Patent Publication Number: US-2023146432-A1

Title: Slidable telecommunications tray with cable slack management

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 17/384,473, filed Jul. 23, 2021; which is a continuation of U.S. application Ser. No. 16/935,907, filed Jul. 22, 2020, now U.S. Pat. No. 11,073,672; which is a continuation of U.S. application Ser. No. 16/273,691, filed Feb. 12, 2019, now U.S. Pat. No. 10,732,371; which is a continuation of U.S. application Ser. No. 15/802,083, filed Nov. 2, 2017, now U.S. Pat. No. 10,209,471; which is a continuation of U.S. application Ser. No. 15/363,016, filed Nov. 29, 2016, now U.S. Pat. No. 9,810,869; which is a continuation of U.S. application Ser. No. 14/830,009, filed on Aug. 19, 2015, now U.S. Pat. No. 9,523,833; which is a continuation of U.S. application Ser. No. 14/169,941, filed on Jan. 31, 2014, now U.S. Pat. No. 9,128,262; which claims priority to U.S. Provisional Application Ser. No. 61/761,009, filed on Feb. 5, 2013; 61/763,347, filed on Feb. 11, 2013; 61/843,744, filed on Jul. 8, 2013; and 61/843,977, filed on Jul. 9, 2013, which applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to fiber optic telecommunications equipment. More specifically, the present disclosure relates to a slidable fiber optic tray or blade designed for high density applications and a rack or frame configured to support a plurality of such fiber optic trays. 
     BACKGROUND 
     In telecommunications industry, the demand for added capacity is growing rapidly. This demand is being met in part by the increasing use and density of fiber optic transmission equipment. Even though fiber optic equipment permits higher levels of transmission in the same or smaller footprint than traditional copper transmission equipment, the demand requires even higher levels of fiber density. This has led to the development of high-density fiber handling equipment. 
     An example of this type of equipment is found in U.S. Pat. No. 6,591,051 (the &#39;051 patent) assigned to ADC Telecommunications, Inc. This patent concerns a high-density fiber distribution frame and high-density fiber termination blocks (FTBs) which are mounted to the frame. Because of the large number of optical fibers passing into and out of the FTBs, the frame and blocks have a variety of structures to organize and manage the fibers. Some structures are used to aid the fibers entering the back of the frame and FTBs. Other structures are provided for managing the cables leaving the FTBs on the front. The FTBs also include structures for facilitating access to the densely packed terminations. One such structure is a slidable adapter module that is incorporated into the FTBs to allow selective access to the densely packed terminations inside the FTBs. 
     Further development in such fiber termination systems is desired. 
     SUMMARY 
     The present disclosure relates to fiber optic telecommunications devices. The telecommunications devices include slidable fiber optic connection trays or blades with features for cable slack management and racks or frames supporting panels or chassis that house such slidable trays in stacked arrangements. 
     According to one aspect of the disclosure, a fiber optic telecommunications device defines a telecommunications chassis for mounting on a telecommunications frame. The chassis includes a plurality of fiber optic trays slidably mounted on the chassis, the fiber optic trays arranged in a vertically stacked arrangement, each fiber optic tray slidable between a closed storage position and an open access position. Each fiber optic tray includes fiber optic connection locations for connecting cables to be routed through the telecommunications frame and a cable manager coupled at a first end to the fiber optic tray and coupled at a second end to the telecommunications chassis. The cable manager is configured for routing cables to and from the fiber optic connection locations, the cable manager defining a plurality of link arms that are pivotally connected to each other such that the cable manager retracts and extends with a corresponding movement of the tray as the link arms pivot with respect to each other, wherein the link arms are configured to pivot relative to each other to prevent fiber optic cables managed therein from being bent in an arc having a radius of curvature that is less than a predetermined value during the movement of the tray. Each link arm defines a top wall, a bottom wall, and two oppositely positioned sidewalls, wherein each link arm defines an open portion along at least one of the sidewalls and an open portion along the top wall for receiving fiber optic cables therein, the open portions along the top wall and the at least one of the sidewalls communicating with each other. 
     According to another aspect of the disclosure, a fiber optic telecommunications device defines a telecommunications rack for mounting a plurality of telecommunications chassis, wherein each chassis includes a plurality of fiber optic trays slidably mounted on the chassis, the fiber optic trays arranged in a vertically stacked arrangement, each fiber optic tray slidable between a closed storage position and an open access position. Each fiber optic tray includes fiber optic connection locations for connecting cables to be routed through the telecommunications frame and a cable manager coupled at a first end to the fiber optic tray and coupled at a second end to the telecommunications chassis, the cable manager configured for routing cables to and from the fiber optic connection locations, the cable manager defining a plurality of link arms that are pivotally connected to each other such that the cable manager retracts and extends with a corresponding movement of the tray as the link arms pivot with respect to each other, wherein the link arms are configured to pivot relative to each other to prevent fiber optic cables managed therein from being bent in an arc having a radius of curvature that is less than a predetermined value during the movement of the tray. Each link arm defines a top wall, a bottom wall, and two oppositely positioned sidewalls, wherein each link arm defines an open portion along at least one of the sidewalls and an open portion along the top wall for receiving fiber optic cables therein, the open portions along the top wall and the at least one of the sidewalls communicating with each other. 
     According to another aspect of the disclosure, a fiber optic tray includes first and second slide portions for slidably mounting the tray to a telecommunications fixture and a connection portion located between the first and second slide portions. Fiber optic connection locations are defined by the connection portion of the tray for connecting cables and a cable manager is coupled at a first end to the fiber optic tray and defines a second end for coupling to the telecommunications fixture receiving the tray. The cable manager is configured for routing cables to and from the fiber optic connection locations, the cable manager defining a plurality of link arms that are pivotally connected to each other such that the cable manager retracts and extends with a corresponding movement of the tray with respect to the fixture as the link arms pivot with respect to each other. The link arms are configured to pivot relative to each other to prevent fiber optic cables managed therein from being bent in an arc having a radius of curvature that is less than a predetermined value during the movement of the tray, each link arm defining a top wall, a bottom wall, and two oppositely positioned sidewalls, wherein each link arm defines an open portion along at least one of the sidewalls and an open portion along the top wall for receiving fiber optic cables therein, the open portions along the top wall and the at least one of the sidewalls communicating with each other. 
     A variety of additional inventive aspects will be set forth in the description that follows. The inventive aspects can relate to individual features and combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a front, right, top partially exploded perspective view of a high-density fiber distribution chassis configured to support a plurality of slidable fiber optic connection trays or blades having features that are examples of inventive aspects in accordance with the principles of the present disclosure mounted in a stacked arrangement thereon; 
         FIG.  2    illustrates the high-density fiber distribution chassis of  FIG.  1    in a partially assembled configuration, shown with a main or master controller circuit board of the chassis being slidably mounted thereon; 
         FIG.  3    illustrates the first and second tray assemblies of the chassis of  FIG.  1    in a partially exploded configuration, the tray assemblies shown outside of the chassis; 
         FIG.  4    illustrates the first and second tray assemblies of  FIG.  3    in an assembled configuration outside of the chassis; 
         FIG.  5    illustrates the first tray assembly of  FIG.  3    in an exploded configuration outside of the chassis; 
         FIG.  6    illustrates the first tray assembly of  FIG.  5    in an assembled configuration; 
         FIG.  7    illustrates the electrical communication pathways via circuit boards for the entire chassis of  FIGS.  1 - 2   ; 
         FIG.  8    illustrates the electrical communication pathways via circuit boards for one of the first trays of  FIG.  6   ; 
         FIG.  9    is a close-up view illustrating the routing of a flexible circuit board in the form of a ribbon cable from a mounting block to one of the trays of the first tray assembly; 
         FIG.  10    is a top cross-sectional view illustrating the routing of the flexible circuit board in the form of a ribbon cable from the center mounting portion of the tray to the fiber optic connection locations of the tray; 
         FIG.  11    is a close-up view of a portion of the flexible circuit board of  FIG.  10    that transitions from the center mounting portion of the tray to the main connection portion of the tray; 
         FIG.  12    is a close-up view of another portion of the flexible circuit board of  FIG.  10    within the center mounting portion of the tray; 
         FIG.  13    illustrates one of the first trays exploded from the mounting block of the first tray assembly; 
         FIG.  14    is a close-up view illustrating the interaction between one of the stop surfaces within one of the channels of the mounting block and one of the stop tabs of a tray of the first tray assembly; 
         FIG.  15    is a cross-sectional view illustrating the center mounting portion of one of the trays within one of the channels of the mounting block of the first tray assembly; 
         FIG.  16    is a perspective cross-sectional view illustrating the interaction between the stop tab of one of the trays and the stop surface within one of the channels of the mounting block when a tray has been pulled fully forwardly with respect to the mounting block; 
         FIG.  17    illustrates a close-up view of the stop tab and the stop surface of  FIG.  16   ; 
         FIG.  18    is a partial exploded view showing the cable management portion of one of the first trays of the first tray assembly of  FIG.  3   , the cable management portion defined at least in part by a link arm assembly that connects between the right end support and the tray of the tray assembly, the link arm assembly formed by a plurality of cable management link arms; 
         FIG.  19    is a close-up view showing the pivotal coupling of the link arm assembly to the right end support of the tray assembly; 
         FIG.  20    is a top, right, front perspective view of the chassis of  FIG.  1    without the top chassis cover mounted thereon to illustrate an example cable routing configuration for one of the first trays within the chassis; 
         FIG.  21    is a top view of the chassis of  FIG.  20    without the chassis cover thereon; 
         FIG.  22    is a perspective view of the chassis of  FIG.  1   , with one of the trays fully pulled out to an open position, illustrating an example cable routing configuration within the tray; 
         FIG.  23    is a perspective view of a first embodiment of a managed connectivity rack housing a plurality of 4RU chassis having features similar to those of the 1RU chassis of  FIG.  1   ; 
         FIG.  24    is a perspective view of the rack of  FIG.  23   , shown without any chassis mounted thereon; 
         FIG.  25    is a perspective view of the rack of  FIG.  23   , shown with a number of the cable management features removed therefrom to illustrate the cable path from the rack controller to the individual chassis mounted within the rack; 
         FIG.  26    is a perspective view of a second embodiment of a managed connectivity rack housing a plurality of 4RU chassis having features similar to those of the 1RU chassis of  FIG.  1   , the second embodiment of the rack having features similar to the rack of  FIGS.  23 - 25   ; 
         FIG.  27    is a perspective view of the rack of  FIG.  26   , shown without any chassis mounted thereon; 
         FIG.  28    is a perspective view of the rack of  FIG.  26   , shown with a number of the cable management features removed therefrom to illustrate the cable path from the rack controller to the individual chassis mounted within the rack; 
         FIG.  29    is a perspective view of a third embodiment of a managed connectivity rack housing a plurality of 4RU chassis having features similar to those of the 1RU chassis of  FIG.  1   , the third embodiment of the rack having features similar to the racks of  FIGS.  23 - 28   ; 
         FIG.  30    is a perspective view of the rack of  FIG.  29   , shown without any chassis mounted thereon; 
         FIG.  31    is a perspective view of the rack of  FIG.  29   , shown with a number of the cable management features removed therefrom to illustrate the cable path from the rack controller to the individual chassis mounted within the rack; 
         FIG.  32    is a rear, top, left perspective view of a rack similar to one of the racks of  FIGS.  23 - 31    shown with a bus-bar mounted thereon for grounding an armored cable; 
         FIG.  33    is a rear, bottom, left perspective view of the rack of  FIG.  32   ; 
         FIG.  34    is a rear view of the rack of  FIG.  32   ; 
         FIG.  35    illustrates the rack of  FIG.  33    with the bus-bar removed from the bus-bar support of the rack; 
         FIG.  36    illustrates a rear, top, left perspective view of the rack of  FIG.  35   ; 
         FIG.  37    illustrates a rear view of the rack of  FIG.  35   ; 
         FIG.  38    is a perspective view of one of the rear horizontal troughs of the rack of  FIGS.  32 - 37    shown in isolation, the horizontal trough configured for mounting the bus-bar support of the rack; 
         FIG.  39    is a front perspective view of the bus-bar support and the bus-bar located therein for mounting to the rack of  FIGS.  32 - 37   ; 
         FIG.  40    is a top view of the bus-bar support and the bus-bar of  FIG.  39   ; 
         FIG.  41    is a bottom view of the bus-bar support and the bus-bar of  FIG.  39   ; 
         FIG.  42    is a front view of the bus-bar support and the bus-bar of  FIG.  39   ; 
         FIG.  43    is a rear perspective view of the bus-bar support and the bus-bar of  FIG.  39   ; 
         FIG.  44    is a perspective view of a top cover of the bus-bar support of the rack of  FIGS.  32 - 37   ; 
         FIG.  45    is a perspective view of a bottom cover of the bus-bar support of the rack of  FIGS.  32 - 37   ; 
         FIG.  46    is a bottom, front perspective view of the bus-bar of the rack of  FIGS.  32 - 37   ; 
         FIG.  47    is a front view of the bus-bar of  FIG.  46   ; 
         FIG.  48    is a bottom view of the bus-bar of  FIG.  46   ; 
         FIG.  49    is a front, right, top partially exploded perspective view of one of the 4RU high-density fiber distribution chassis shown removed from the racks of  FIGS.  23 - 37   ; 
         FIG.  50    illustrates the high-density fiber distribution chassis of  FIG.  49    in a partially assembled configuration, shown with a main or master controller circuit board of the chassis being slidably mounted thereon; 
         FIG.  51    illustrates the first and second tray assemblies of the chassis of  FIG.  49    in a partially exploded configuration, the tray assemblies shown outside of the chassis; 
         FIG.  52    illustrates the first and second tray assemblies of  FIG.  51    in an assembled configuration outside of the chassis; 
         FIG.  53    illustrates the first tray assembly of  FIG.  51    in an exploded configuration outside of the chassis; 
         FIG.  54    illustrates the first tray assembly of  FIG.  53    in an assembled configuration; 
         FIG.  55    illustrates the electrical communication pathways via circuit boards for the entire chassis of  FIGS.  49 - 50   ; 
         FIG.  56    is a partial exploded view showing the cable management portion of one of the first trays of the first tray assembly of  FIG.  51   ; 
         FIG.  57    is a close-up view showing the pivotal coupling of the link arm assembly of the first tray to a right end support of the tray assembly of  FIG.  56   ; 
         FIG.  58    is a top, right, front perspective view of the chassis of  FIG.  49    without the top chassis cover mounted thereon to illustrate an example cable routing configuration for one of the first trays within the chassis; 
         FIG.  59    is a close-up view of the cable management portion of the first tray of the first tray assembly of  FIG.  58   ; 
         FIG.  60    is a top view of the chassis of  FIG.  58    without the chassis cover thereon; 
         FIG.  61    is a perspective view of the chassis of  FIG.  49   , with one of the trays fully pulled out to an open position, illustrating an example cable routing configuration within the tray; 
         FIG.  62    is a front, right, top perspective view of another embodiment of a 1RU high-density fiber distribution chassis configured to support a plurality of slidable fiber optic connection trays or blades having features that are examples of inventive aspects in accordance with the principles of the present disclosure mounted in a stacked arrangement thereon, the chassis of  FIG.  62    including features similar to the 1RU chassis of  FIGS.  1 - 22   ; 
         FIG.  63    is a partially exploded view of the chassis of  FIG.  62   ; 
         FIG.  64    is a partially exploded view of the chassis of  FIG.  63   , shown with the top chassis cover removed completely to illustrate the tray assemblies mounted therein, the cable management portions for two of the trays shown exploded off the chassis; 
         FIG.  65    illustrates the chassis of  FIG.  64    with the trays shown exploded off the chassis; 
         FIG.  66    illustrates the chassis of  FIG.  65    with the ends supports and the center divider assembly of the chassis shown exploded off the chassis; 
         FIG.  67    illustrates the center divider assembly of the chassis in an exploded configuration; 
         FIG.  68    illustrates the right end support of the chassis in an exploded configuration, the right end support configured to house the main controller or PCB of the chassis; 
         FIG.  69    is a side view of the removable end cap of the right end support of the chassis, the end cap shown with the end cap cover removed to illustrate the end cap lever features; 
         FIG.  70    illustrates one of the first trays of the first tray assembly of the chassis of  FIGS.  62 - 65    in isolation with the cable management portion of the tray removed; 
         FIG.  71    is a partially exploded view of the tray of  FIG.  70    with the tray PCB cover exploded off the tray; 
         FIG.  71 A  is a close-up view of a portion of the tray of  FIG.  71   ; 
         FIG.  72    is a fully exploded view of the tray of  FIG.  70   , with portions of the slide assembly of the tray removed to illustrate the features thereof; 
         FIG.  73    is a top view of the slide assembly of the tray with the top cover of the center rail of the slide assembly removed to illustrate the routing of the flexible circuit board in the form of a ribbon cable within the slide assembly; 
         FIG.  74    illustrates a partially exploded view of the mounting rail of the slide assembly of  FIG.  72   ; 
         FIG.  74 A  is a close-up view of a portion of the tray of  FIG.  74   ; 
         FIG.  75    illustrates the tray of  FIG.  70    removed from the slide assembly of  FIG.  72   , the tray defining a main connection portion, a center mounting portion, and a side mounting portion; 
         FIG.  76    illustrates an exploded view of a cable management portion of one of the first trays of the first tray assembly of the chassis of  FIGS.  62 - 65   ; 
         FIG.  77    illustrates a portion of a fully assembled configuration of the cable management portion of the first tray of  FIG.  76   ; 
         FIG.  78    illustrates an exploded view of a cable management portion of one of the second trays of the second tray assembly of the chassis of  FIGS.  62 - 65   ; 
         FIG.  79    illustrates the electrical communication pathways via circuit boards for the entire chassis of  FIG.  62   ; 
         FIG.  80    illustrates a mounting panel for the top PCB of the chassis, the mounting panel configured to mount the top PCB to the top chassis cover of the chassis of  FIG.  62   . 
         FIG.  81    is a perspective view of another embodiment of a pivot door that can be used with the chassis of  FIGS.  62 - 80   ; 
         FIG.  82    is a partially exploded view of the pivot door of  FIG.  81   ; 
         FIG.  82 A  is a close-up view of a portion of the pivot door of  FIG.  82   ; 
         FIG.  83    is another exploded view of the pivot door of  FIG.  81   ; 
         FIG.  84    is a close-up, rear view of the spring latch mechanism of the door of  FIG.  81    with the cover removed; 
         FIG.  85    is a close-up, front view of the spring latch mechanism in isolation removed from the door of  FIG.  81   , the spring latch mechanism shown in a latched position; 
         FIG.  86    illustrates the spring latch mechanism of  FIG.  85    in an unlatched or open position; 
         FIG.  87    illustrates another version of a link arm assembly including a compression spring assembly provided between a first link arm and a second link arm connected thereto; 
         FIG.  87 A  is a close-up view of a portion of the link arm assembly of  FIG.  87   ; 
         FIG.  88    illustrates the link arms of  FIG.  87    from a top view; 
         FIG.  89    illustrates the compression spring assembly exploded off the first link arm of  FIG.  87   ; 
         FIG.  90    is a perspective view of a spring housing of the compression spring assembly of  FIG.  87   ; 
         FIG.  91    is a top view of the spring housing of  FIG.  90   ; 
         FIG.  92    is a bottom view of the spring housing of  FIG.  90   ; 
         FIG.  93    is a perspective view of a slider of the compression spring assembly of  FIG.  87   ; 
         FIG.  94    is another perspective view of the slider of  FIG.  93   ; 
         FIG.  95    is a front view of the slider of  FIG.  93   ; 
         FIG.  96    illustrates a perspective view of the link arm assembly of  FIG.  87    with a pair of first fanouts mounted on the first link arm; 
         FIG.  97    illustrates another perspective view of the link arm assembly of  FIG.  96   ; 
         FIG.  98    illustrates a top view of the link arm assembly of  FIG.  96   ; 
         FIG.  99    illustrates the first fanouts exploded from the first link arm of the link arm assembly of  FIG.  96   ; 
         FIG.  100    is a cross-sectional view taken along a line  100 - 100  of  FIG.  98   ; 
         FIG.  101    illustrates a perspective view of the link arm assembly of  FIG.  87    with a pair of second fanouts mounted on the first link arm; 
         FIG.  102    illustrates another perspective view of the link arm assembly of  FIG.  101   ; 
         FIG.  103    illustrates a top view of the link arm assembly of  FIG.  96   ; 
         FIG.  104    illustrates the second fanouts exploded from the first link arm of the link arm assembly of  FIG.  101   ; 
         FIG.  105    illustrates in an exploded configuration one of the second fanouts and a fanout holder used for mounting one of the second fanouts to the first link arm of the link arm assembly of  FIG.  101   ; 
         FIG.  106    is a front perspective view of the second fanout and the fanout holder of  FIG.  105    in an assembled configuration; 
         FIG.  107    is a rear perspective view of the second fanout and the fanout holder of  FIG.  106   ; 
         FIG.  108    is a top view of the second fanout and the fanout holder of  FIG.  106   ; 
         FIG.  109    is a bottom view of the second fanout and the fanout holder of  FIG.  106   ; 
         FIG.  110    is a side view of the second fanout and the fanout holder of  FIG.  106   ; 
         FIG.  111    is a front view of the second fanout and the fanout holder of  FIG.  106   ; 
         FIG.  112    is a front perspective view of the fanout holder of  FIG.  105    shown in isolation; 
         FIG.  113    is a rear perspective view of the fanout holder of  FIG.  112   ; 
         FIG.  114    is a top view of the fanout holder of  FIG.  112   ; 
         FIG.  115    is a bottom view of the fanout holder of  FIG.  112   ; 
         FIG.  116    is a side view of the fanout holder of  FIG.  112   ; 
         FIG.  117    is a front view of the fanout holder of  FIG.  112   ; 
         FIG.  118    is a rear view of the fanout holder of  FIG.  112   ; 
         FIG.  119    illustrates another embodiment of a slide assembly for mounting a tray such as the tray of  FIG.  70    to a chassis, the slide assembly shown in a partially exploded configuration; 
         FIG.  119 A  illustrates a close-up view of the locking features of the slide assembly of  FIG.  119    for locking the tray at pulled-out positions or at a central position within the chassis; 
         FIG.  120    is a top view of the slide assembly of  FIG.  119    with the top cover of the center rail of the slide assembly removed to illustrate the internal locking features thereof; 
         FIG.  120 A  is a close-up view of a front end portion of the slide assembly of  FIG.  120   ; 
         FIG.  120 B  is a close-up view of a rear end portion of the slide assembly of  FIG.  120   ; 
         FIG.  121    illustrates the slide assembly of  FIG.  119    when the tray is at a forward, pulled-out position; 
         FIG.  121 A  is a close-up top view of a front end portion of the slide assembly of  FIG.  121   ; and 
         FIG.  121 B  is a close-up top view of a rear end portion of the slide assembly of  FIG.  121   . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to examples of inventive aspects of the present disclosure which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     The fiber optic telecommunications devices shown in  FIGS.  1 - 48    are high density distribution racks or frames and panels or chassis mounted therein, wherein each chassis or panel is configured to house a plurality of slidable trays or blades. The trays are configured to support multiple fiber optic connections. According to one embodiment, the panels or the racks housing the panels can be managed devices wherein the connections can be monitored to verify that the connectors have been installed into the correct connection locations (e.g., adapters) and have not been disturbed. The panels may be available in 1-rack-unit (1RU) and 4-rack-unit (4RU) sizes. According to one embodiment, the 1RU panels may house 144 mated LC connector pairs, 72 SC connector pairs or 48 MPO connector pairs. The 4RU panels may house four times the number of connections as the 1RU units with the same functionality. 
     Within each panel and within each tray or blade, the connection locations defined by, for example, an adapter block assembly, which is used to connect fiber optic connectors, may be accessible from both the front and the back of the panel. An adapter block assembly may be installed onto a sliding tray and may reside toward the center portion of the panel. Using a portion of the tray which may define a pull handle or a pull arm, the tray can be slid forward to access the front connections of the adapter block assembly. The cables attached to the front connectors may be managed using a link arm assembly made up of four cable management link arms, which swing forward and out of the way for access to the front of the adapter block assembly. When a technician is done accessing/loading the front connectors, using the aforementioned pull arm, the tray is pushed back to its central location. The tray, as well as a torsion spring located within the link arm that is connected directly to one of the end supports of the tray assembly, pull the cable management link arms back into the panel as the tray is pushed back into place by the technician. 
     To access or load the back-side of the adapter block assemblies, a technician can, from the back of the panel, pull the tray out the other side, moving the link arms to manage the cables on the back side as well. 
     According to one example embodiment, there may be a total of six trays per 1RU panel, each housing an adapter block assembly capable of holding 24 LC connections, for a total of 6×24=144 connections. According to one example, the trays may be stacked three high on each side (i.e., first side and second side) of the panel. Each tray may use link arms on both the front and back sides to manage incoming and outgoing cables. The link arms are configured to allow cables to be installed and removed from both the tops and the sides of the link arms. The link arms are designed such that, regardless of position of the moving tray, the cables contained therewithin do not violate the minimum bend radius requirements. The longest link arm that is directly attached to one of the end supports of the tray assembly may be designed to hold two fanouts, which are devices that transition fiber from one high-fiber-count cable to multiple single-fiber-count cables. 
     On each tray, a technician may attach a 24-port adapter block assembly using a snap fit mounting arrangement on the tray. For managed panels, the adapter block assemblies may include a printed circuit board (PCB) installed thereonto, which connects to each connector installed using contacts within the adapter openings and a chip on each connector. The PCB on the adapter block assembly may connect to the tray using a multi-pin connector on the tray. The connector on the tray may be attached to a flexible circuit formed from a ribbon cable that routes to a central PCB within the chassis. The ribbon cable may be looped within a cavity defined by the pull arm or pull handle of the tray to allow the tray to travel back and forth without disrupting the communication through the ribbon cable between the central PCB and the adapter block assembly PCB. The central PCB may use indicators in the form of light emitting diodes (LEDs) on both the front and back of the panel to communicate to a technician which tray should be accessed. The central PCB then may connect to a main PCB (i.e., a main controller), which is housed within one of the end supports of the tray assembly. The connection is made via another ribbon cable that runs along a top cover of the chassis into the end support. The main PCB or controller is accessible to the technician by removing a front end cap of the applicable end support. The main controller may use a card-edge-style connection at its opposite rear end to connect to the ribbon cable that runs along the cover, allowing the main controller to be a field-replaceable device. The main controller is configured to communicate to a higher-level managed connectivity rack or frame via a connection (e.g., an RJ connection) on the side of the panel. The main controller of the panel may be powered via another connection on the side of the panel. 
     The above aspects of the telecommunications device will now be described in further detail below. 
     Referring specifically now to  FIGS.  1 - 6   , the high-density fiber distribution chassis or panel  10  is shown in various views. In  FIG.  1   , the chassis  10  is shown in an exploded view with a plurality of slidable fiber optic connection trays or blades  12  mounted thereon. The chassis  10  defines a bottom plate  14  with upwardly extending sidewalls  16 , a top chassis cover  18 , and a pair of mounting brackets  20  that are configured to be fastened to the sidewalls  16 . The mounting brackets  20  are used for mounting the chassis  10  to other fixtures such as telecommunications racks or frames. The bottom plate  14 , including the upwardly extending sidewalls  16 , and the top cover  18  define fastener openings  22  for mounting a tray assembly  24  within the chassis  10 . The mounting brackets  20  of the chassis  10  are also fastened to fastener openings  22  on the sidewalls  16  of the chassis  10 . 
     In the depicted embodiment, the chassis  10  is configured as a standard 1RU (rack unit) piece. In other embodiments, the chassis  10  may be configured to have different sizes. According to one example embodiment, the chassis  10  may be configured as a 4RU device. Such an example of a chassis is shown in  FIGS.  23 - 37    as mounted on a telecommunications rack  40 , as will be discussed in further detail below. 
     Still referring to  FIGS.  1 - 6   , as noted above, each chassis  10  is configured to house tray assemblies  24 . In the depicted embodiment, the tray assemblies  24  may be defined by a first tray assembly  24   a  that is located on the right side of the chassis  10  and a second tray assembly  24   b  that is located on the left side of the chassis  10 . Each of the tray assemblies  24  may include a plurality of slidable trays  12  mounted in a stacked arrangement. For example, the first tray assembly  24   a , as shown, may include three first trays  12   a  to be mounted in a stacked arrangement and the second tray assembly  24   b  may include three second trays  12   b  to be mounted in a stacked arrangement, wherein the chassis  10  can house six total slidable trays  12  in the depicted version. 
     The first and second tray assemblies  24   a ,  24   b  are generally similar in configuration and for ease of description, only the first tray assembly  24   a  will be described in detail, with the understanding that the features of the first tray assembly  24   a  are fully applicable to the second tray assembly  24   b  except for the noted differences. In addition, in the drawings, only one representative first tray  12   a  and one representative second tray  12   b  have been shown for ease of illustration. Thus, in the present disclosure, only one of the first trays  12   a  will be shown and described in detail, with the understanding that the features of that first tray  12   a  are fully applicable to other first trays  12   a  that might be mounted in a stacked arrangement therewith or to other second trays  12   b  that might be mounted on the left side of the chassis  10 . 
     Referring specifically now to  FIGS.  3  and  4   , the first and second tray assemblies  24   a ,  24   b  are shown outside of the chassis  10  of  FIGS.  1  and  2   . In  FIG.  3    specifically, the first and second tray assemblies  24   a ,  24   b  are shown in an exploded configuration where they have been separated from each other. As discussed previously and as will be discussed in further detail below, the two tray assemblies  24 , when mounted together, capture a central PCB  28  therebetween. The central PCB  28  may include indicators in the form of LEDs  30  on both the front  32  and the back  34  of the chassis  10  to communicate to a technician which tray  12  should be accessed. As will be discussed in further detail below, all of the trays  12  of both the first tray assembly  24   a  and the second tray assembly  24   b  electrically connect to the central PCB  28 . And, the central PCB  28  is electrically connected to a main PCB or controller  36  of the chassis  10 , wherein the main PCB  36  of the chassis  10  is configured to communicate to a higher-level managed connectivity rack or frame  40 . 
     Referring now to  FIG.  5   , the different parts of the first tray assembly are illustrated in an exploded configuration. The first tray assembly includes the central PCB  28 , a mounting plate  38 , a mounting block  42 , a first tray  12   a , an end support  44 , and the main PCB  36  to be mounted to the end support  44 . As noted above and as will be described in further detail below, a flexible circuit in the form of a ribbon cable  46  provides an electrical connection between the central PCB  28  and a PCB  48  located on the tray  12  and another ribbon cable  50  provides the connection between the central PCB  28  and the main PCB or controller  36  of the chassis  10 . The ribbon cable  50  is configured to run along the top cover  18  of the chassis  10 , and, via the central PCB  28 , can connect both the first and second tray assemblies  24   a ,  24   b  to the main PCB  36 . 
     The mounting plate  38  of the first tray assembly  24   a , which along with a mounting plate  38  of the second tray assembly  24   b , is configured for capturing the central PCB  28  and mounting the central PCB  28  and the mounting blocks  42  of the tray assemblies  24  to the chassis  10 . The mounting plate  38  defines tabs  52  with fastener openings  54  that are aligned with fastener openings  56  of the central PCB  28  for mounting the central PCB  28  to the bottom plate  14  and top cover  18  of the chassis  10 . The mounting plate  38  also includes fastener openings  58  on a sidewall thereof for fastening the mounting blocks  42  thereto and to the chassis  10 . 
     As will be discussed in further detail, each tray  12  is configured to be slidably captured between the mounting block  42  and the end support  44  of the tray assembly  24 . For the first tray assembly  24   a , for example, the end support  44  defines fastener openings  60  for mounting to the right sidewall  16  of the chassis  10 , capturing the main PCB  36  thereagainst. The end support  44  defines a channel  62  for housing the main PCB  36 . As shown in  FIG.  2   , the main PCB  36  may be slidably loaded into the channel  62  of the end support  44 . The main PCB  36  is accessible to a technician by removing a front end cap  64  of the end support  44 . The main controller  36  may use a card-edge-style connection at its opposite rear end to connect to the ribbon cable  50  that runs along the chassis top cover  18 , allowing the main controller  36  to be a field-replaceable device. A side cap  68  is used at the rear end of the end support  44  to cover a card-edge-style connector  66 . It should be noted that in the depicted embodiment of the chassis  10 , since both tray assemblies  24  are being connected through the central PCB  28 , only the end support  44  of the first tray assembly  24   a  defines a channel  62  for supporting the main controller  36 , wherein the end support  44  of the second tray assembly  24   b  is not shown as housing a main controller or PCB  36 . This configuration may be modified depending upon the orientation of the chassis  10  within a given rack  40 . 
     Referring now to  FIGS.  5  and  8 - 14   , each tray  12  of each tray assembly  24  defines a main connection portion  70 , a center mounting portion  72 , a side mounting portion  74 , and a cable management portion  76 . The center mounting portion  72  of the tray  12  is configured for slidable coupling to the mounting block  42  that is located generally toward the center of the chassis  10 . The side mounting portion  74  of the tray  12  is configured for slidable coupling to an end support  44  of the tray assembly  24  that is located generally close to one of the sides of the chassis  10 . 
     Both the mounting block  42  and the end support  44  include longitudinally extending channels provided in a stacked arrangement. The channels  78  of the mounting block  42  are configured to slidably receive the center mounting portion  72  of each tray  12 . The channels  80  of the end support  44  are configured to receive the side mounting portion  74  of each tray  12 . 
     Referring now to the interaction between the side mounting portions  74  of the trays  12  and the channels  80  of the end support  44 , the side mounting portions  74  and the channels  80  of the end support  44  define matching dovetail configurations for providing slidable movement and preventing lateral separation. 
     Regarding the interaction between the center mounting portions  72  of the trays  12  and the channels  78  of the central mounting block  42 , the center mounting portions  72  may define pull handles or arms  82  at both the front and rear ends of the center mounting portions  72 . Using the pull handles  82 , the trays  12  can be slid forward to access the front connections within the trays  12  or slid rearward to access the rear connections within the trays  12 . 
     As shown in detail in  FIG.  13   , both the top and bottom sides  84 ,  86  of the center mounting portion  72  of a tray  12  define longitudinal tracks  88 . The tracks  88  receive guides  90  located within the channels  78  of the mounting block  42  for slidably guiding the trays  12 . The guides  90  are located adjacent the front  92  and the rear  94  of the channels  78  of the mounting block  42 . 
     Within the channels  78  of the mounting block  42  are also located flexible tabs  96  on both the top and bottom walls  98 ,  100  defining each channel  78 . The tabs  96  cooperate with depressions  102  located within the tracks  88  of the center mounting portion  72  of the tray  12  to provide temporary stops for the tray  12 . In this manner, the trays  12  may be stopped at discrete intermittent positions such as at a center position within the chassis  10  or when pulled forwardly or rearwardly. 
     In addition, each channel  78  and the center mounting portion  72  of each tray  12  also define positive stops to prevent removal of the trays  12  when the trays  12  are pulled fully forwardly or fully rearwardly. The positive stops are defined first by a stop surface  104  adjacent the front end  92  of the channel  78  and a stop surface  104  adjacent the rear end  94  of the channel  78 . The stop surfaces  104  are defined at ends of top and bottom longitudinal recesses  106  within the channel  78  as seen in  FIG.  15   . The other portion of the positive stops between the tray  12  and the mounting block  42  are defined on the trays  12 . As shown in  FIGS.  13 - 16   , the center mounting portion  72  of each tray  12  defines a stop tab  108  adjacent the front end  110  of the center mounting portion  72  and a stop tab  108  adjacent the rear end  112  of the center mounting portion  72 . The stop tab  108  at the front end  110  extends outwardly from the top side  84  of the center mounting portion  72  and the stop tab  108  at the rear end  112  extends outwardly from the bottom side  86  of the center mounting portion  72 . 
     As shown in  FIG.  15   , the stop surface  104  adjacent the front  92  of the channel  78  of the mounting block  42  is positioned toward the bottom wall  100  of the channel  78  and the stop surface  104  adjacent the rear  94  of the channel  78  of the mounting block  42  is positioned toward the top wall  98  of the channel  78 . Thus, when a tray  12  is pulled fully forwardly, the rear stop tab  108  (which is located at the bottom side  86 ) contacts the front stop surface  104  within the channel  78 . When a tray  12  is pulled fully rearwardly, the front stop tab  108  (which is located at the top side  84 ) contacts the rear stop surface  104  within the channel  78 . As noted above, the top and bottom stop tabs  108  of the center mounting portion  72  are normally accommodated by the top and bottom longitudinal recesses  106  within each channel  78  until they encounter the stop surfaces  104  at the respective ends. 
     The main connection portion  70  of the tray  12  is located between the center mounting portion  72  and the side mounting portion  74  and is configured to define connection locations  114  for the tray  12 . By stacking a plurality of the trays  12  on a distribution chassis  10 , density of connections for fiber optic transmission can be increased and the slidability of the trays  12  in either the front direction or the rear direction provides for easy access at both the front and the rear of the distribution chassis  10 . 
     As shown in  FIGS.  8 - 9   , the depicted version of the main connection portion  70  of the tray  12  includes a mount  116  for mounting fiber optic adapters  118  which define the fiber optic connection locations  114  in the present embodiment of the tray  12 . Specifically, in the tray  12  shown and described in the present application, the fiber optic connection locations  114  are defined by adapters  118  having an LC type footprint. In the depicted embodiments, twenty-four LC adapters  118  are mounted to the mount  116  via a snap-fit connection defined on the mount  116 . In the high density distribution chassis  10  shown in the present disclosure, six slidable trays  12  may be mounted on a 1RU of rack space, providing 144 LC connections as noted above. 
     As noted earlier, other standards of fiber optic adapters  118  (such as SC or MPO adapters) can be mounted to the mount  116 . Fiber optic adapters  118  are only one type of fiber optic equipment that provides connection locations  114  for the tray  12  and the tray  12  can be used with other types of fiber optic equipment. For example, equipment such as fiber optic splitters, couplers, multiplexers/demultiplexers, or other types of equipment wherein cables may be routed away from the connection locations  114  may be housed on the main connection portion  70 . 
     If fiber optic adapters  118  are used, the connection locations  114  may be defined by adapters  118  individually mounted in the mount  116  or may be defined by adapter block assemblies  120  that include integrally formed adapters  118  in block form, as shown in the depicted embodiment. In other embodiments, the connection locations  114  may be in the form of a cassette that may include fiber optic adapters  118  on one side wherein the opposite side may have a multi-fiber connector or a cable extending outwardly therefrom, with optical fibers normally housed within such a cassette. 
     Examples of devices that may define the connection locations such as the adapter block assemblies  120  or cassettes are illustrated and described in further detail in U.S. Pat. Nos. 9,423,570; 9,285,552; and 9,379,501, which are all incorporated by reference in their entireties. 
     As noted previously, the chassis or panels may be available in 1-rack-unit (1RU) and 4-rack-unit (4RU) sizes. The 1RU panels may house 144 mated LC connector pairs (as shown), 72 SC connector pairs or 48 MPO connector pairs. The 4RU panels may house four times the number of connections as the 1RU units with the same functionality. 
     Within each panel  10  and within each tray  12 , the connection locations  114  may be accessible from both the front and the back of the panel  10 . For example, as shown, an adapter block assembly  120  may be installed on a sliding tray  12  such that it resides toward the center portion of the panel  10 . Using the pull handles or arms  82  discussed above, the tray  12  can be slid forwardly or rearwardly to access the front connections or the rear connections of the adapter block assembly  120 . 
     Cable management is an important aspect of a high density distribution panel or frame when managing a high density of cables extending from the front and rear ends of the adapter block assemblies  120  that may be mounted on the trays  12 . 
     As discussed above, each tray  12  is configured to include a cable management portion  76  for managing cables  122  from the connection locations  114  to and away from the chassis  10  both for the cables  122  extending from the front ports of the adapters  118  and from the rear ports of the adapters  118 . The cable management portions  76  of the trays  12  are configured such that they accommodate any cable slack during the forward and rearward slidable movements of the trays  12 , while maintaining minimum bend radius requirements of the cables  122 . Also, the cable management portions  76  of the trays  12  are designed to keep the same length of cabling from the connection locations  114  to the exterior of the chassis  10  so as to prevent any pulling or pinching of the cables  122  and to limit the need for excess slack cabling. 
     The cable management portion  76  of each tray  12  may be defined by a front cable management portion  76   a  and a rear cable management portion  76   b . It should be noted that the front and rear cable management portions  76   a ,  76   b  are similar in configuration and only the front cable management portion  76   a  will be discussed herein for ease of description, with the understanding that all of the inventive features of the front cable management portion  76   a  of a given tray  12  are fully applicable to the rear cable management portion  76   b.    
     Referring now to  FIGS.  13  and  18 - 22   , the front cable management portion  76   a  is defined by a radius limiter  124  that is located adjacent the side mounting portion  74  of the tray  12  and a link arm assembly  126  made up of four cable management link arms  128 , which are attached between the radius limiter  124  and the front of the end support  44  of the tray assembly  24 . 
     The link arms  128  are configured to swing forwardly and out of the way for access to the front of the adapter block assembly  120  when the tray  12  is pulled forwardly. When a technician is done accessing and/or loading the front connectors, using the aforementioned pull arm  82 , the tray  12  is pushed back to its original closed location. 
     The link arms  128  are defined by four link arms that are pivotally coupled with respect to each other so as to define a limited pivotal movement therebetween. The four link arms include a first link arm  128   a  that is directly pivotally coupled to the front of the end support  44  of the tray assembly  24  via a hinge assembly  130 . The hinge assembly  130  defines a hinge pin  132  that is inserted through openings  134  on both the end support  44  and the first link arm  128   a  for the pivotal coupling. As shown in  FIGS.  18  and  19   , the hinge assembly  130  also defines a torsion spring  136 , one end of which is inserted into a longitudinal pocket  138  at the front of the end support  44  and a second (perpendicular) end which is inserted into a pocket  140  provided on the first link arm  128   a . The torsion spring  136  is configured to bias the link arm assembly  126  into its original closed position wherein the torsion spring  136  pulls the cable management link arms  128  back into the panel  10  as the tray  12  is pushed back into place by the technician, whether the tray  12  is being pulled forwardly or rearwardly. A similar torsion spring is also provided on the rear cable management portion  76   b  of the tray  12  assisting the torsion spring  136  of the front cable management portion  76   a  in biasing the tray  12  back into a closed position. 
     In the depicted embodiment, the cable management portion  76  of the trays  12  are configured for top and side loading of the cables thereinto. As shown in  FIGS.  13 ,  20   , and  21 , the radius limiter  124  defines a generally curved cable channel  142  with inwardly extending cable management fingers  144  for retaining cables  122  once therein. In such an example, the cables  122  can be top loaded into the radius limiter  124  as they extend from the connection locations  114 . 
     The first link arm  128   a  is pivotally connected to the end support  44  such that it can move between a transverse position when the tray  12  is closed to a longitudinal orientation when the tray  12  is fully open as shown in  FIG.  22   . A contact surface  146  defined on the first link arm  128   a  prevents further movement of the first link arm  128   a  with respect to the end support  44 . The remaining three link arms  128   b  of the link arm assembly  126  are configured to have the same shape as each other. Each of the three similar link arms  128   b  is coupled back to back from the first link arm  128   a  to the radius limiter  124  of the tray  12 . The link arms  128   b  include snap-fit coupling features defined, for example, by cylindrical tabs  148  on a first male end  150  and cylindrical receptacles  152  on an opposite second female end  154  for providing the pivotal movement. Each of the link arms  128   b , as in the first link arm  128   a , defines contact surfaces  156  such that they are limited in their pivotal movement with respect to each other. For example, the link arm  128   b  that is directly coupled to the first link arm  128   a  might define a contact surface  156  to prevent further pivotal movement with respect thereto when the tray  12  is fully open. Each of the link arms  128  including the first link arm  128   a  is designed such that regardless of position of the moving tray  12 , the cables  122  contained therewithin will not violate the minimum bend radius requirements. 
     According to one example embodiment, as shown in  FIGS.  20  and  21   , the link arms  128  may be designed for top and side loading of the cable  122 , wherein cable management tabs  158  might be located on the peripheral edges  160 . Other configurations are certainly possible for the link arms  128 . 
     The first link arm  128   a  that is directly attached to one of the end supports  44  of the tray assembly  24  may be designed to hold structures such as fanouts, which are devices that transition fiber from one high-fiber-count cable to multiple single-fiber-count cables  122 . 
     Example cable routing configurations have been shown in  FIGS.  20 - 22   . The cables  122  lead from both the front and rear connection locations  114  through the radius limiters  124  and through each of the three similar link arms  128   b  and finally through the first link arm  128   a  before being directed out of the chassis  10 . As noted above, the front link arm assembly  126   a  and the rear link arm assembly  126   b  are configured to move simultaneously together to manage the cable slack as the trays  12  are pulled out from either direction. 
     Referring now to  FIGS.  8 ,  13 ,  18 ,  20 , and  21   , the cable management portion  76  of the trays  12  may also include cable retainers  5  that extend between the center mounting portion  72  and the radius limiter  124 . The cable retainers  5  are pivotally coupled to the center mounting portion  72  of the tray assembly  24  at a first end  6  via a hinge assembly  7  defined by both the center mounting portion  72  and the first end of the cable retainer  5 . The cable retainer  5  includes a snap-fit tab  8  at a second end  9  thereof that is configured to be inserted into a receptacle  3  defined adjacent the radius limiter  124  for interlocking the cable retainer  5  at a closed or pivoted-down position with a snap-fit. The cable retainers  5  are configured to hold or retain cables extending from the connection locations  114  when in a pivoted-down position. The cable retainers can be pivoted up and out of the way by the technician to access the connection locations  114 . 
     Referring now to  FIGS.  7 - 12   , as noted above, in accordance with some aspects, certain types of adapters  118  that are mounted to the trays  12  in the form of adapter block assemblies  120  may be configured to collect physical layer information from one or more fiber optic connectors received thereat. For example, certain types of adapters  118  of the adapter block assemblies  120  may include a body configured to hold one or more media reading interfaces that are configured to engage memory contacts on the fiber optic connectors. One or more media reading interfaces may be positioned in the adapter body. In certain implementations, the adapter body may define slots extending between an exterior of the adapter body and an internal passage in which the ferrules of the connectors are received. 
     Certain types of media reading interfaces may include one or more contact members that are positioned in the slots. A portion of each contact member may extend into a respective one of the passages to engage memory contacts on a fiber optic connector. Another portion of each contact member may also extend out of the slot to contact a circuit board that may be positioned on the adapter block assembly  120 . As noted, portions of the tray  12  and the chassis  10  may define conductive paths that are configured to connect the media reading interfaces of the adapters  118  with a main controller or PCB  36  of the chassis  10 , which can further communicate with a controller of the rack  40  that is housing the chassis  10 . 
     The main controller  36  of the chassis  10  or the controller of the rack  40  may include or connect (e.g., over a network) to a processing unit that is configured to manage physical layer information obtained by the media reading interfaces. 
     According to the depicted example embodiment, on each tray  12 , once a technician attaches a 24-port adapter block assembly  120  using snap features on the tray  12 , the adapter block assemblies  120  may plug into the network as discussed above. For such managed panels  10 , for example, the printed circuit boards of the adapter block assemblies  120  may connect to the tray  12  using multi-pin connectors  162  on the tray  12  as shown in  FIGS.  7 ,  8 , and  10   . The multi-pin connectors  162  on the tray  12  may be attached to a flexible circuit formed by a ribbon cable  46  that routes to a central PCB  28  within the panel  10 . As shown, the conductive pathway from the multi-pin connectors  162  to the ribbon cable  46  is provided by a printed circuit board  48  that is located at a central divider portion  164  of the tray  12  and also by a portion  45  of the flexible ribbon cable  46  that is positioned horizontally along the rear side  166  of the main connection portion  70  of the tray  12 . The printed circuit board  48  and the horizontal portion  45  of the ribbon cable  46  are preferably mounted flush within recesses  168  provided on the central divider  164  and the rear side  166  of the main connection portion  70  of the tray  12 . 
     A portion  47  of the ribbon cable  46 , which is provided in a vertical orientation, may be looped within a cavity  170  defined by the center mounting portion  72  of the tray  12  as shown in  FIGS.  10 - 12   . The vertical portion  47  of the ribbon cable  46  is configured to move within the cavity  170  to allow the tray  12  to travel back and forth without disrupting the communication through the ribbon cable  46  between the central PCB  28  and tray PCB  48 . An end  172  of the ribbon cable  46  extends through a slot  174  on the left wall  176  of the center mounting portion  72  of the tray  12  to connect to the central PCB  28 . Another slot  178  is provided on the right wall  180  of the center mounting portion  72  of the tray  12  to allow a portion of the ribbon cable  46  to extend from inside the cavity  170  to the main connection portion  70  of the tray  12 , wherein the ribbon cable  46  transitions from a vertical orientation to a flat horizontal orientation by a twist of the cable  46 . 
     The end  172  of the ribbon cable  146 , after passing though the slot  174  on the left wall of the center mounting portion  72  of the tray, extends through slots  175  on the mounting block  42  and then slots  177  on the mounting plate  38 , before making a connection with a connector  179  on the central PCB  28 . 
     As noted above, the central PCB  28  may use indicators such as LEDs  30  on both the front  32  and back  34  of the panel  10  to communicate to a technician which tray  12  should be accessed. The central PCB  28  then may connect to the main PCB or controller  36  of the chassis  10 , which is housed within the end support  44  of the tray assembly  24 . The connection is made via another ribbon cable  50  that runs along a top cover  18  of the panel  10  into the end support  44 . The ribbon cable  50  is configured to extend to the card-edge-style connector  66  that is located toward the rear of the channel  62 . The main controller  36  is accessible to the technician by removing a front end cap  64  of the applicable end support  44 . The main controller  36  may use a card-edge-style connection with the connector  66  at its opposite rear end to connect to the ribbon cable  50  that runs along the top cover  18 , allowing the main controller  36  to be a field-replaceable device. The main controller  36  is configured to communicate to a higher-level managed connectivity rack or frame  40  via a connection on the side of the panel  10 . The main controller  36  of the panel  10  may be powered via another connection on the side of the panel  10 . 
     Referring now to  FIGS.  23 - 31   , three different examples of a managed connectivity racks or frames  40  are shown. In the example embodiments of the racks  40  shown, the racks  40  are configured for housing chassis  1010  that are 4RU in size. The main controller or PCB of the 4RU chassis  1010  is designed to communicate with twenty four trays  12  and may be provided at a location different than the location discussed for a 1RU chassis  10  (of  FIGS.  1 - 22   ) which is designed to communicate with six trays  12 . In the 1RU chassis  10 , each chassis  10  is illustrated as having the main controller  36  embedded in an end support  44  of the chassis  10 . According to one example, for the 4RU chassis  1010 , the main controller may be positioned within a channel located in an end support of the tray assemblies, similar to the 1RU version of the chassis  10 , as will be described in further detail with respect to  FIGS.  49 - 61   . Other locations are possible for the chassis main controller. 
     Still referring to  FIGS.  23 - 31   , the managed connectivity racks  40  are designed to include a rack controller  41  that communicates with each chassis  1010  mounted within the rack  40 . The three different examples of the racks  40  illustrate different methods of routing the cabling  222  from the rack controller  41  to the individual chassis  1010  mounted within the rack  40 . 
     Except for the way the cabling  222  is routed from the rack controller  41  to the individual chassis  1010 , all depicted versions of the racks  40  share certain similar features. Such features will generally be discussed with reference to one of the versions, with the understanding that the features are fully applicable to the other versions. 
     Referring now to  FIGS.  23 - 25   , a first embodiment of a managed connectivity rack  40   a  housing a plurality of 4RU chassis  1010  having features similar to those of the 1RU chassis  10  of  FIG.  1    is shown. As noted above, the first embodiment of the rack  40   a  shares certain features with the other two versions. In  FIG.  24   , the rack  40   a  is shown without any chassis  1010  mounted thereon and in  FIG.  25   , the rack  40   a  is shown with a number of cable management features removed therefrom to illustrate the cable path from the rack controller  41  to the individual chassis  1010  mounted within the rack  40   a.    
     Still referring to  FIGS.  23 - 25   , at the front  230 , the rack  40   a  includes front-to rear troughs  232  that communicate with rear horizontal troughs  234  at the rear  236  of the rack  40   a . Cable loops  238  are provided adjacent both the right and left sides  240 ,  242  of the rack  40   a , wherein the cable loops  238  are located within right and left front vertical cable channels  244 ,  246  defined on the right and left sides  240 ,  242  of the chassis  40   a , respectively. In the depicted embodiment, the rack  40   a  also includes cable slack management spools  249  at the left side  242  of the rack  40   a , wherein the spools  249  are provided in a stacked arrangement along a column at the left side  242  of the rack  40   a , at the front  230  thereof. 
     At the rear  236  of the rack  40   a , the rack  40   a  defines vertical cable guides or channels  248 ,  250 , respectively, on both the right and left sides  240 ,  242  of the rack  40   a  extending along the height of the rack  40   a . Please see  FIGS.  32  and  34    for the rear view of a similar rack  40   d . A cross-frame trough  252  is provided for each chassis or panel  1010  and connects the vertical cable guides  248 ,  250  on the right and left sides  240 ,  242 . A radius limiter in the form of a trumpet flare  254  is provided on the left end of the cross-frame trough  252 . A second trumpet flare  256  is provided below the first trumpet flare  254  on the left side  242  of the rack  40   a . At the right side  240  of the rack  40   a , a plurality of radius limiters  258  (e.g., spools) is located within the right vertical cable guide or channel  248 . Still referring to  FIGS.  23 - 25   , the rack  40   a  also includes the rear horizontal troughs  234  extending between the right side  240  and the left side  242  of the rack  40   a . The front-to-rear troughs  232  provided at each of the right and left sides  240 ,  242  of the rack  40   a  provide for the routing of cables  122  between the front side  230  and the rear side  236  of the rack  40   a.    
     The cable routing within the rack  40   a  for cables  122  extending from the front connection locations  114  and rear connection locations  114  of the trays  12  of the individual chassis  1010  are similar in configuration to those example routings described in U.S. Pat. Nos. 9,069,150 and 9,057,859, the entire disclosures of which are incorporated herein by reference in their entireties. 
     Racks  40  illustrated in  FIGS.  26 - 31    generally follow the same construction and routing configuration as the rack  40   a  illustrated in  FIGS.  23 - 25   . 
     As noted above, the three different versions of the racks illustrated in  FIGS.  23 - 31    all include controllers  41  that are configured to communicate with the individual chassis  1010  mounted on the racks  40 . 
     In the depicted embodiments of the racks  40 , the racks  40  are configured to hold six 4RU chassis  1010 . In such an embodiment, the frame controller  41  may contain an 8-port Ethernet switch, one of which may be used to route data from each 4RU chassis main controller to an Infrastructure Configuration Manager (ICM). A local microprocessor may be attached to the Ethernet switch which allows the processor to access an Address Translation Unit of the Ethernet switch and look up the Media Access Control Address of each 4RU chassis main controller connected to the frame  40  by specific ports (e.g., six different ports allowing for six chassis  1010  to be managed). This allows mapping of each switch port to the Media Access Control Addresses of the attached chassis main controller. Each switch port may relate to a specific location in the frame  40 . The Media Access Control Addresses and related Ethernet switch port data can be sent to the Infrastructure Configuration Manager, which may use the data to determine which frame each 4RU chassis main controller is installed in, and the location of each 4RU main controller within the frame  40 . An auxiliary Ethernet port may be provided for local access to each 4RU chassis main controller or the rack controller  41 . A Power over Ethernet powered Wi-Fi access point can optionally be added to allow mobile devices access to each 4RU chassis main controller, or the frame controller  41 . Further aspects of the managed connectivity of the rack  40  and the chassis  10 / 1010  mounted thereon is described in Examples of devices that may define the connection locations such as the adapter block assemblies  118  or cassettes are illustrated and described in further detail in U.S. Pat. No. 9,507,113, which is incorporated by reference in its entirety. 
     Regarding the routing of the cabling  222  from the Ethernet ports of the controller  41  of the rack  40  to the individual 4RU chassis  1010 , in the first version of the rack  40   a  shown in  FIGS.  23 - 25   , the rack  40   a  defines a single vertical bracket  260  with openings  262  that allow breakout points  223  of the cables  222  to extend therethrough. The vertical bracket  260  is mounted to the right vertical frame member  264  and is configured to contain the cabling  222  extending from the controller  41  as shown in detail in  FIG.  25   , wherein the rack  40   a  is shown with a number of cable management features removed therefrom to illustrate the cable path. The vertical bracket  260  defines a plurality of mounting flanges  266  for fastening to the right vertical frame member  264  of the rack  40   a.    
     In the second version of the rack  40   b  shown in  FIGS.  26 - 28   , the rack  40   b  defines a plurality of individual brackets  268  having cable management tabs  269  that are mounted to the right vertical frame member  264  of the rack  40   b . The brackets  268  are configured to provide cable breakouts  223  at either the top side or the bottom sides of the brackets  268 . The brackets  268  are positioned depending upon where the main controller for each 4RU chassis  1010  may be located. 
     In the third version of the rack  40   c  shown in  FIGS.  29 - 31   , the rack  40   c  may include a plurality of clips  270  that are configured to be mounted to cross frame members  272  that extend between the right vertical frame member  264  of the rack  40   c  and the left vertical frame member  274 . According to one embodiment, the clips  270  may be adhesively attached. The cables  222  that are contained by the clips  270  can breakout at the desired locations. 
     In such a version of the rack  40   c , the rack  40   c  does not have to be previously modified (e.g., requiring mounting holes on the vertical frame members  264 / 274 , etc.) and, thus, the routing of the cabling  222  from the controller  41  to the individual chassis  1010  may be characterized as a retrofit arrangement. 
     Referring now to  FIGS.  32 - 37   , there is shown an embodiment of a rack  40   d  similar to those of  FIGS.  23 - 31    that includes a bus-bar  280  mounted thereon for grounding an armored cable. The cabling coming into a rack  40  from a central office (e.g., an IFC cable) for further distribution might include armored cabling having grounded shielding surrounding the cable bundle. Each of the cables of the bundle may be grounded using the bus-bar  280  mounted on the rack  40   d.    
     According to one example mounting arrangement, the bus-bar  280  may be housed in a bus-bar support  282  that is mounted to the bottom  233  of the uppermost rear horizontal trough  234 . 
     The bus-bar support  282  is shown in  FIG.  39 - 45   . It should be noted that the bus-bar support  282  that is depicted in the application is simply one example structure that may be used. Other support structures or enclosures may be used. In the depicted example, the bus-bar support  282  defines a top cover  284  and a bottom cover  286  that is fastened to the top cover  284 . The top cover  284  may define mounting flanges  288  that are slidably inserted into receptacles  290  defined at the bottom  233  of the uppermost rear horizontal trough  234 . The uppermost rear horizontal trough  234  is shown in isolation, removed from the rack  40   d , in  FIG.  38   . The top cover  284  of the bus-bar support  282  defines projections  292  which receive a main plate  294  of the bus-bar  280  and the bottom cover  286  captures the bus-bar  280  with respect to the top plate  284 . 
     The bus-bar  280  is shown in isolation in  FIGS.  46 - 48   . Even though the bus-bar  280  is described and shown as being mounted to the uppermost rear horizontal trough  234 , other locations are also possible for the mounting of the bus-bar  280  in the rack  40   d.    
     According to another aspect of the racks  40  discussed in the present application, the racks  40  may include a light source. The light source may provide visual assistance to a technician in locating a rack  40  in an environment where light may be limited. The light source may be provided in various forms and may be positioned at various locations on the rack  40  for illuminating the rack  40  and the connection locations  114  thereof. 
     Referring now to  FIGS.  49 - 61   , one of the 4-rack-unit (4RU) panels  1010  that have been shown mounted on the racks  40  of  FIGS.  23 - 37    is illustrated in further detail. Except for the differences that will be discussed in detail, the 4RU versions of the panels  1010  are similar in configuration and functionality to the 1RU versions and are designed to slidably receive the same fiber optic connection devices as the 1RU panels  10 . For example, as shown in  FIGS.  49 - 61   , the 4RU panels  1010  may be sized to fit twenty-four trays  12  (i.e., twelve first trays  12   a  in a stacked arrangement on the right side of the chassis  1010  and twelve second trays  12   b  in a stacked arrangement on the left side of the chassis  1010 ). Within those trays  12 , whereas the 1RU panels  10  (shown in  FIGS.  1 - 32   ) may house 144 mated LC connector pairs, 72 SC connector pairs or 48 MPO connector pairs, the 4RU versions  1010  may house four times the number of connections as the 1RU units with the same functionality. As will be discussed in further detail below, the trays  12  mounted within the 4RU panels  1010  form parts of tray assemblies  1024  similar to those tray assemblies  24  of 1RU panels  10 . 
     As discussed above, the connection locations within the trays  12  within the 4RU panels  1010  may be managed similar to the connection locations within the 1RU panels  10 . As will be discussed in further detail below, for managed 4RU panels, similar to 1RU panels, a connection between a central PCB  1028  within the panel  1010  and a main PCB or controller  1036  of the panel  1010  may be established via ribbon cables that run within the panel  1010 . Similar to the 1RU versions of the panels  10 , in a 4RU panel  1010 , the main controller  1036  may use a card-edge-style connection  1066  at its opposite rear end to connect to the ribbon cable(s), allowing the main controller  1036  to be a field-replaceable device. As shown in  FIGS.  23 - 31   , the main controller  1036  of the 4RU panel  1010 , similar to the 1RU version, is configured to communicate to a higher-level managed connectivity rack or frame  40  via a connection  1077  (e.g., an RJ connection) on the side of the panel  1010 . The main controller  1036  of the panel  1010  may be powered via another connection  1079  on the side of the panel  1010 . 
     Further aspects of the 4RU panel  1010  will now be described below with reference to  FIGS.  49 - 61   . 
     Referring to  FIGS.  49 - 61   , the high-density fiber distribution chassis or panel  1010  is shown in various views. In  FIG.  49   , the chassis  1010  is shown in an exploded view with a plurality of slidable fiber optic connection trays or blades  12  mounted thereon. The chassis  1010  defines a bottom plate  1014  with upwardly extending sidewalls  1016 , a top chassis cover  1018 , and a pair of mounting brackets  1020  that are configured to be fastened to the sidewalls  1016 . The mounting brackets  1020  are used for mounting the chassis  1010  to other fixtures such as telecommunications racks or frames. The bottom plate  1014 , including the upwardly extending sidewalls  1016 , and the top cover  1018  define fastener openings  1022  for mounting tray assemblies  1024  within the chassis  1010 . The mounting brackets  1020  of the chassis  1010  are also fastened to the fastener openings  1022  on the sidewalls  1016  of the chassis  1010 . A pair of spacer plates  1011  are mounted to the bottom plate  1014  of the chassis  1010 . The spacer plates  1011  are positioned underneath the stacked trays  12 . The spacer plates cooperatively define a notch  1013  extending from the front to the back of the chassis  1010  for accommodating the central PCB  1028  and mounting plates  1038  that are attached at each side of the central PCB  1028 , which extend further down than the trays  12 . 
     In the depicted embodiment, the chassis  1010  is configured as a standard 4RU (4-rack-unit) piece. The chassis  1010  is configured to house four times as many trays  12  as the 1RU chassis  10  described previously. 
     Still referring to  FIGS.  49 - 61   , as noted above, each chassis  1010  is configured to house tray assemblies  1024 . In the depicted embodiment, similar to the 1RU chassis  10 , the tray assemblies  1024  may be defined by a first tray assembly  1024   a  that is located on the right side of the chassis  1010  and a second tray assembly  1024   b  that is located on the left side of the chassis  1010 . Each of the tray assemblies  1024  may include a plurality of slidable trays  12  mounted in a stacked arrangement. For example, the first tray assembly  1024   a , as shown, may include twelve first trays  12   a  to be mounted in a stacked arrangement and the second tray assembly  1024   b  may include twelve second trays  12   b  to be mounted in a stacked arrangement, wherein the chassis  1010  can house twenty-four total slidable trays  12  in the depicted version. 
     The first and second tray assemblies  1024   a ,  1024   b  are generally similar in configuration and for ease of description, only the first tray assembly  1024   a  will be described in detail, with the understanding that the features of the first tray assembly  1024   a  are fully applicable to the second tray assembly  1024   b  except for the noted differences. In addition, in a number of the drawings (e.g.,  FIGS.  53 - 54   ), only one representative first tray  12   a  has been shown for ease of illustration. Thus, in the present disclosure, only one of the first trays  12   a  will be shown and described in detail, with the understanding that the features of that first tray  12   a  are fully applicable to other first trays  12   a  that might be mounted in a stacked arrangement therewith or to other second trays  12   b  that might be mounted on the left side of the chassis  1010 . 
     Referring specifically now to  FIGS.  51  and  52   , the first and second tray assemblies  1024   a ,  1024   b  are shown outside of the chassis  1010  of  FIGS.  49  and  50   . In  FIG.  51    specifically, the first and second tray assemblies  1024   a ,  1024   b  are shown in an exploded configuration where they have been separated from each other. As discussed previously and as will be discussed in further detail below, the two tray assemblies  1024 , when mounted together, capture a central PCB  1028  therebetween. The central PCB  1028  may include indicators in the form of LEDs  1030  on both the front  1032  and the back  1034  of the chassis  1010  to communicate to a technician which tray  12  should be accessed. Similar to the 1RU panel  10 , all of the trays  12  of both the first tray assembly  1024   a  and the second tray assembly  1024   b  electrically connect to the central PCB  1028 . And, the central PCB  1028  is electrically connected to a main PCB or controller  1036  of the chassis  1010 , wherein the main PCB  1036  of the chassis  1010  is configured to communicate to a higher-level managed connectivity rack or frame  40 . 
     Referring now to  FIGS.  51 - 54   , the different parts of the first tray assembly  1024   a  are illustrated. The first tray assembly  1024   a  includes the central PCB  1028 , a mounting plate  1038 , four of the mounting blocks  42  from the 1RU chassis  10  (only one shown), a first tray  12   a , a first end support  1044   a , a second end support  1044   b  that is stacked on top of the first end support  1044   a , and the main PCB  1036  to be mounted to the first end support  1044   a . As noted above, similar to the 1RU panel  10 , a flexible circuit in the form of the ribbon cable  46  provides an electrical connection between the central PCB  1028  and the PCB  48  located on the tray  12 . And, a pair of ribbon cables  1050   a  and  1050   b  provide a connection between the central PCB  1028  and the main PCB or controller  1036  of the chassis  1010 . The ribbon cables  1050   a  and  1050   b  are configured to run underneath the trays  12 , along the top of one of the spacer plates  1011  of the chassis  1010 . Via the central PCB  1028 , the ribbon cables  1050   a  and  1050   b  can connect both the first and second tray assemblies  1024   a ,  1024   b  to the main PCB  1036 . The central PCB  1028  includes a first connection point  1029   a  for the ribbon cable  1050   a  and a second connection point  1029   b  for the ribbon cable  1050   b.    
     The mounting plate  1038  of the first tray assembly  1024   a , which along with a mounting plate  1038  of the second tray assembly  1024   b , is configured for capturing the central PCB  1028  and mounting the central PCB  1028  and the mounting blocks  42  of the tray assemblies  1024  to the chassis  1010 . The mounting plate  1038  defines tabs  1052  with fastener openings  1054  that are aligned with fastener openings  1056  of the central PCB  1028  for mounting the central PCB  1028  to the bottom plate  1014  and to the top cover  1018  of the chassis  1010 . The mounting plate  1038  also includes fastener openings  1058  on a sidewall thereof for fastening the mounting blocks  42  (four in a stacked arrangement on each mounting plate  1038 ) thereto and to the chassis  1010 . 
     Each tray  12  is configured to be slidable between the mounting blocks  42  and the end supports  1044   a ,  1044   b  of the tray assembly  1024 . For the first tray assembly  1024   a , for example, the end supports  1044   a ,  1044   b  define fastener openings  1060  for mounting to the right sidewall  1016  of the chassis  1010 . The first end support  1044   a  defines a channel  1062  for housing the main PCB  1036 . As shown in  FIG.  50   , the main PCB  1036  may be slidably loaded into the channel  1062  of the first end support  1044   a . The main PCB  1036  is accessible to a technician by removing a front end cap  1064  of the first end support  1044   a . The main controller  1036  may use a card-edge-style connection at its opposite rear end to connect to the ribbon cables  1050   a ,  1050   b . The card-edge-style connection allows the main controller  1036  to be a field-replaceable device. A rear end cap  1068  is also positioned at the rear end of the first end support  1044   a . As in the 1RU panel  10 , since both tray assemblies  1024  are being connected through the central PCB  1028 , only the first end support  1044   a  of the first tray assembly  1024   a  defines a channel  1062  for supporting the main controller  1036 . In the depicted embodiment, the end supports  1044   a ,  1044   b  of the second tray assembly  1024   b  are not shown as housing a main controller or PCB  1036 . This configuration may be modified depending upon the orientation of the chassis  1010  within a given rack  40 . 
     As in the 1RU panel  10 , the side mounting portion  74  of the tray  12  is configured for slidable coupling to the end supports  1044   a  and  1044   b  of the tray assembly  1024 . The end supports  1044   a ,  1044   b  include longitudinally extending channels  1080  provided in a stacked arrangement. The channels  1080  of the end supports  1044   a ,  1044   b  are configured to receive the side mounting portion  74  of each tray  12 . As in the 1RU panel  10 , the side mounting portions  74  and the channels  1080  of the end supports  1044   a ,  1044   b  define matching dovetail configurations for providing slidable movement and preventing lateral separation. 
     The cable management portions of the trays are coupled to the end supports  1044   a  and  1044   b  in a similar manner to that shown and described for the 1RU panel  10 . 
     Referring now to  FIGS.  56  and  57   , the first link arm  128   a  is directly pivotally coupled to the front of the end supports  1044   a ,  1044   b  of the tray assembly  1024  via a hinge assembly  1130 . The hinge assembly  1130  defines a hinge pin  1132  that is inserted through openings  1134  on both the end supports  1044   a ,  1044   b  and the first link arm  128   a  for the pivotal coupling. As shown in  FIGS.  56  and  57   , the hinge assembly  1130  also includes the torsion spring  136 , one end of which is inserted into a longitudinal pocket  1138  at the fronts of the end supports  1044   a ,  1044   b  and a second (perpendicular) end which is inserted into the pocket  140  provided on the first link arm  128   a . As in the 1RU chassis  10  described above, the torsion spring  136  is configured to bias the link arm assembly  126  into its original closed position wherein the torsion spring  136  pulls the cable management link arms  128  back into the panel  1010  as the tray  12  is pushed back into place by the technician, whether the tray  12  is being pulled forwardly or rearwardly. A similar torsion spring is also provided on the rear cable management portion  76   b  of the tray  12  assisting the torsion spring  136  of the front cable management portion  76   a  in biasing the tray  12  back into a closed position. 
     Example cable routing configurations have been shown in  FIGS.  58 - 61    for the 4RU chassis. The cables  122  lead from both the front and rear connection locations  114  through the radius limiters  124  and through each of the three similar link arms  128   b  and finally through the first link arm  128   a  before being directed out of the chassis  1010 . As noted previously, the front link arm assembly  126   a  and the rear link arm assembly  126   b  are configured to move simultaneously together to manage the cable slack as the trays  12  are pulled out from either direction. 
     As described above with respect to the 1RU chassis  10 , portions of the tray  12  and the chassis  1010  may define conductive paths that are configured to connect media reading interfaces of adapters  118  mounted within the tray  12  with the main controller or PCB  1036  of the chassis  1010 , which can further communicate with a controller of the rack  40  that is housing the chassis  1010 . 
     The main controller  1036  of the chassis  1010  or the controller of the rack  40  may include or connect (e.g., over a network) to a processing unit that is configured to manage physical layer information obtained by the media reading interfaces. 
     Referring now to  FIGS.  53 - 55   , according to the depicted example embodiment, on each tray  12 , once a technician attaches a 24-port adapter block assembly  120  using snap features on the tray  12 , the adapter block assemblies  120  may plug into the network as discussed above. For such managed panels  1010 , for example, the printed circuit boards of the adapter block assemblies  120  may connect to the tray  12  using the multi-pin connectors  162  on the tray  12  as shown in  FIG.  55   . The multi-pin connectors  162  on the tray  12  may be attached to a flexible circuit formed by the ribbon cable  46  that routes to the central PCB  1028  within the panel  1010 . As shown, the conductive pathway from the multi-pin connectors  162  to the ribbon cable  46  is provided by the printed circuit board  48  that is located at a central divider portion  164  of the tray  12  and also by a portion  45  of the flexible ribbon cable  46  that is positioned horizontally along the rear side  166  of the main connection portion  70  of the tray  12 . 
     As described above for the 1RU panels  10 , a portion  47  of the ribbon cable  46 , which is provided in a vertical orientation, is looped within the cavity  170  defined by the center mounting portion  72  of the tray  12  (as shown previously in  FIGS.  10 - 12   ). The vertical portion  47  of the ribbon cable  46  is configured to move within the cavity  170  to allow the tray  12  to travel back and forth without disrupting the communication through the ribbon cable  46  between the central PCB  1028  and the tray PCB  48 . An end  172  of the ribbon cable  46  extends through a slot  174  on the left wall  176  of the center mounting portion  72  of the tray  12  to connect to the central PCB  1028 . Another slot  178  is provided on the right wall  180  of the center mounting portion  72  of the tray  12  to allow a portion of the ribbon cable  46  to extend from inside the cavity  170  to the main connection portion  70  of the tray  12 , wherein the ribbon cable  46  transitions from a vertical orientation to a flat horizontal orientation by a twist of the cable  46 . 
     For each tray  12 , the end  172  of the ribbon cable  146 , after passing though the slot  174  on the left wall of the center mounting portion  72  of the tray, extends through slots  175  on the mounting blocks  42  and then slots  1177  on the mounting plate  1038 , before making a connection with a connector  1179  on the central PCB  28 . 
     As noted above, the central PCB  1028  may use indicators such as LEDs  1030  on both the front  1032  and back  1034  of the panel  1010  to communicate to a technician which tray  12  should be accessed. The central PCB  1028  then may connect to the main PCB or controller  1036  of the chassis  1010 , which is housed within the first end support  1044   a  of the tray assembly  1024 . The connection is made via ribbon cables  1050   a ,  1050   b  that run to the first end support  1044   a . The ribbon cables  1050   a  and  1050   b  are configured to extend to the card-edge-style connector  1066  that is located within the channel  1062  of the first end support  1044   a . The main controller  1036  is accessible to a technician by removing the front end cap  1064  of the first end support  1044   a . The main controller  1036  may use the card-edge-style connection with the connector  1066  at its opposite rear end to connect to the ribbon cables  1050   a ,  1050   b , allowing the main controller  1036  to be a field-replaceable device. 
     As shown in  FIGS.  23 - 37   , the main controller  1036  is configured to communicate to a higher-level managed connectivity rack or frame  40  via a connection (e.g., connection  1077 ) on the side of the panel  1010 . The main controller  1036  of the panel  1010  may be powered via another connection (e.g., connection  1079 ) on the side of the panel  1010 . 
       FIGS.  62 - 80    illustrate another embodiment of a 1RU high-density fiber distribution chassis configured to support a plurality of slidable fiber optic connection trays or blades having features that are examples of inventive aspects in accordance with the principles of the present disclosure. As will be described in further detail below, the chassis  2010  of  FIGS.  62 - 80    includes features similar to the 1RU chassis of  FIGS.  1 - 22   . The chassis  2010  of  FIGS.  62 - 80    also includes features that are different than the 1RU chassis of  FIGS.  1 - 22   , as will be discussed in further detail. For example, the chassis  2010  is configured to house slidable trays or blades that are completely physically and electrically removable from the chassis and replaceable with other trays or blades. 
     As in the previous examples of devices shown in  FIGS.  1 - 61   , the fiber optic telecommunications device shown in  FIGS.  62 - 80    is a panel or chassis that is configured to be mounted in a high density distribution rack or frame. The chassis or panel is configured to house a plurality of slidable trays or blades. The trays are configured to support multiple fiber optic connections. According to one embodiment, the panel or the rack housing the panel can be managed devices wherein the connections can be monitored to verify that the connectors have been installed into the correct connections locations (e.g., adapters) and have not been disturbed. Even though the panel described herein and shown in  FIGS.  62 - 80    is a 1-rack-unit (1RU) panel, versions that include 4-rack-unit (4RU) sizes may be provided. 
     As in the previous 1RU chassis described above and shown in  FIGS.  1 - 22   , within the panel and within each tray or blade, the connection locations defined by, for example, an adapter block assembly, which is used to connect fiber optic connectors, may be accessible from both the front and the back of the panel. An adapter block assembly may be installed onto a sliding tray and may reside toward the center portion of the panel. Using a portion of the tray which may define a pull or slide lever, the tray can be slid forward to access the front connections of the adapter block assembly. The cables attached to the front connectors may be managed using a link arm assembly made up of five cable management link arms, which swing forward and out of the way for access to the front of the adapter block assembly. When a technician is done accessing/loading the front connectors, using the aforementioned pull or slide lever, the tray is pushed back to its central location. The tray, as well as an extension spring located within the link arm assembly are configured to pull the cable management link arms back into the panel as the tray is pushed back into place by the technician. 
     To access or load the back-side of the adapter block assemblies, a technician can, from the back of the panel, pull the tray out the other side, moving the link arms to manage the cables on the back side as well. 
     As in the previous example 1RU panel, according to one example embodiment, there may be a total of six trays per 1RU panel, each housing an adapter block assembly capable of holding 24 LC connections, for a total of 6×24=144 connections. According to one example, the trays may be stacked three high on each side (i.e., first side and second side) of the panel. Each tray may use link arms on both the front and back sides to manage incoming and outgoing cables. The link arms are configured to allow cables to be installed and removed from both the tops and the sides of the link arms. The link arms are designed such that, regardless of position of the moving tray, the cables contained therewithin do not violate the minimum bend radius requirements. The longest link arm that is directly attached to one of the end supports of the tray assembly may be designed to hold two fanouts, which are devices that transition fiber from one high-fiber-count cable to multiple single-fiber-count cables. 
     On each tray, a technician may attach a 24-port adapter block assembly using a snap fit mounting arrangement on the tray. For managed panels, the adapter block assemblies may include a printed circuit board (PCB) installed thereonto, which connects to each connector installed using contacts within the adapter openings and a chip on each connector. The PCB on the adapter block assembly may connect to the tray using multi-pin connectors on the tray. The connectors on the tray may be attached to a flexible circuit in the form of a ribbon cable that routes to a central PCB within the chassis. The ribbon cable may be flexibly routed within a slide assembly of the tray to allow the tray to travel back and forth without disrupting the communication through the ribbon cable between the central PCB and the adapter block assembly PCB. The slide assembly of each tray may house a micro slide PCB that is configured to be electrically connected to the central PCB when the trays are mounted to the chassis. The micro slide PCB of each removable tray may use indicators in the form of light emitting diodes (LEDs) to communicate to a technician which tray should be accessed. The central PCB then may connect to a main PCB (i.e., a main controller), which is housed within one of the end supports of the tray assembly of the chassis. The connection is made via another top PCB that runs along a top cover of the chassis into the end support. The main PCB or controller may be a removable device and may be accessible to the technician by removing a front end cap of the end support. The main controller may use a card-edge-style connection at its opposite rear end to connect to a backplane PCB housed within the end support. The top PCB that runs along the cover connects the central PCB to the backplane PCB and thus to the main controller using card-edge-style connections. The main controller of the chassis is configured to communicate to a higher-level managed connectivity rack or frame via a connection (e.g., an RJ connection) on the side of the panel. The main controller of the panel may be powered via another connection on the side of the panel. 
     The above aspects of the telecommunications device will now be described in further detail below. 
     Referring specifically now to  FIGS.  62 - 69   , the high-density fiber distribution chassis or panel  2010  is shown in various views. The chassis  2010  is shown with a plurality of slidable fiber optic connection trays or blades  2012  mounted thereon. As will be described in further detail below, the trays  2012  are configured to be completely removable, both physically and electrically, from the chassis  2010  and replaceable with other similar trays. 
     The chassis  2010  defines a bottom plate  2014  with upwardly extending sidewalls  2016 , a top chassis cover  2018 , and a pair of mounting brackets  2020  that are configured to be fastened to the sidewalls  2016  (see  FIG.  63   ). The mounting brackets  2020  are used for mounting the chassis  2010  to other fixtures such as telecommunications racks or frames  40 . The bottom plate  2014 , including the upwardly extending sidewalls  2016 , and the top cover  2018  define fastener openings  2022  for mounting tray assemblies  2024  within the chassis  2010 . The mounting brackets  2020  of the chassis  2010  are also fastened to fastener openings  2022  on the sidewalls  2016  of the chassis  2010 . 
     In the depicted embodiment, as discussed above, the chassis  2010  is configured as a standard 1RU (rack unit) piece. In other embodiments, the chassis  2010  may be configured to have different sizes. According to one example embodiment, the chassis may be configured as a 4RU device. Such an example of a chassis is shown in  FIGS.  23 - 37    as mounted on a telecommunications rack  40 . 
     Still referring to  FIGS.  62 - 69   , as noted above, each chassis  2010  is configured to house tray assemblies  2024 . In the depicted embodiment, the tray assemblies  2024  may be defined by a first tray assembly  2024   a  that is located on the right side of the chassis  2010  and a second tray assembly  2024   b  that is located on the left side of the chassis  2010 . Each of the tray assemblies  2024  may include a plurality of slidable trays  2012  mounted in a stacked arrangement. For example, the first tray assembly  2024   a , as shown, may include three first trays  2012   a  to be mounted in a stacked arrangement and the second tray assembly  2024   b  may include three second trays  2012   b  to be mounted in a stacked arrangement, wherein the chassis  2010  can house six total slidable trays  2012  in the depicted version. 
     As shown in  FIG.  65   , in the depicted embodiment of the chassis  2010 , the first tray assemblies  2024   a  are removable from the front side of the chassis and the second tray assemblies  2024   b  are removable from the rear side of the chassis. Each tray is slidable both in the forward and the rearward direction with respect to the chassis  2010 . 
     As shown in  FIG.  62   , the chassis defines a pair of pivot doors  2003  at each of the front end  2032  and the rear end  2034  of the chassis  2010 . The pivot doors  2003  protect the first and second tray assemblies  2024  within the chassis  2010 . Both of the pivot doors  2003  at the front end  2032  and the at the rear end  2034  share a pivot hinge  2011  and pivot about the same pivot axis to provide access to the tray assemblies  2024  within the chassis  2010 . The pivot doors  2003  define latches  2013  at the ends opposite from the pivot hinge  2011  for locking the pivot doors  2003  at a closed position. The latches  2013  may define flexible portions that are configured to snap into detents  2015  located at the top chassis cover  2018  and the bottom plate  2014  of the chassis  2010 , adjacent the end supports  2044 . 
       FIGS.  81 - 86    illustrate another example of a pivot door  3003  that can be used with the chassis  2010  of the present application. The pivot door  3003  includes a spring latch mechanism  3005  that allows a user to latch and unlatch the door  3003 . 
     Referring to  FIGS.  81 - 86   , at a first end  3007 , the pivot door  3003  defines a pivot pin  3009  for cooperating with the pivot hinge  2011  of the chassis  2010  for pivotally opening the door  3003  to provide access to the tray assemblies  2024  within the chassis  2010 . At a second end  3011 , the pivot door  3003  defines the spring latch mechanism  3005  that allows the user to latch the door  3003  at a closed position and unlatch the pivot door  3003  to an open position. 
     The spring latch mechanism  3005  includes a slide latch  3013  that is configured to be captured against the second end  3011  of the door  3003  with a cover  3015 . The cover  3015  is fastened to the second end  3011  of the door  3003  with a fastener  3017 . The slide latch  3013  is configured to have limited sliding movement between the cover  3015  and the door  3003  and is spring-biased to an extended position (i.e., a closed or a latched position) as will be discussed below. 
     The slide latch  3013  defines guide slots  3019  that cooperate with guide tabs  3021  on the door  3003  for allowing the slide latch  3013  to slide between the extended position and a depressed position (i.e., an open or an unlatched position). The abutment of the guide tabs  3021  with ends  3023  of the guide slots  3019  provide the positive stops in limiting the sliding movement of the slide latch  3013 . 
     Still referring to  FIGS.  81 - 86   , the spring  3025  providing the biasing force on the slide latch  3013  is positioned within a spring pocket  3027  defined on the slide latch  3013 . The spring  3025  abuts a first end  3029  of the spring pocket  3027  at a first end  3031  of the spring  3025  and a spring stop  3033  defined on the door  3003  at a second end  3035  of the spring  3025 . In this manner, the spring  3025  is captured between the slide latch  3013  and a structure that is on the door  3003  and is able to bias the slide latch  3013  away from the door  3003 . 
     The slide latch  3013  defines a pair of angled pin tracks  3037  that are configured to receive pins  3039  of two opposing locking tabs  3041 . The locking tabs  3041  are configured to slidably move in a direction generally perpendicular to that of the movement of the slide latch  3013 . The locking tabs  3041 , similar to the slide latch  3013 , also include guide tabs  3045  that slidably fit within guide slots  3047  defined on the cover  3015  for guiding and limiting the movement of the locking tabs  3041 . The guide tabs  3045  are located on an opposite face of the locking tabs  3041  from the pins  3039 . 
     The locking tabs  3041  include locking ends  3049  with a tapered face  3051  and an opposing flat face  3053 . The locking ends  3049  are configured to snap into the detents  2015  located at the top chassis cover  2018  and the bottom plate  2014  of the chassis  2010 , adjacent the end supports  2044 . The flat faces  3053  of the locking ends  3049  need to be cleared off the detents  2015  in order to pivot the door  3003  to an open position. 
     As shown in  FIGS.  85 - 86   , when the slide latch  3013  is pushed inwardly toward the door  3003  and the spring  3025  is depressed, the locking tabs  3041  are pulled toward the slide latch  3013  due to the camming action between the angled pin tracks  3037  and the pins  3039  of the locking tabs  3041 . When the locking tabs  3041  have cleared the detents  2015 , the door  3003  can be pivoted open. 
     The spring  3025  biases the slide latch  3013  outwardly to an extended position. Due to the camming action between the angled pin tracks  3037  and the pins  3039  of the locking tabs  3041 , the locking tabs  3041  are also pushed outwardly away from the slide latch  3013  due to the spring  3025 . When a user needs to close the pivot door  3003 , the user can simply push the pivot door  3003  to a closed position and the tapered faces  3051  of the locking ends  3049  of the locking tabs  3041  allow the locking tabs  3041  to snap-fit into the detents  2015  on the chassis  2010 . The tapered faces  3051  of the locking ends  3049  abut the front edge of the top chassis cover  2018  and the front edge of the bottom plate  2014  of the chassis  2010  to provide the slight inward movement needed for the locking tabs  3041  to clear the top chassis cover  2018  and the bottom plate  2014  of the chassis  2010  and snap into the detents  2015 . 
     The pivot door  3003 , although illustrated and described for a 1RU chassis, may be modified for use with a 4RU chassis with a similar spring latch mechanism. 
     Now referring back to  FIG.  64   , a partially exploded view of the chassis  2010  is shown with the top chassis cover  2018  removed completely to illustrate the tray assemblies  2024  mounted therein, the cable management portions for two of the trays  2012  shown exploded off the chassis  2010 . 
     The first and second tray assemblies  2024   a ,  2024   b  are generally similar in configuration and for ease of description, only the first tray assembly  2024   a  will be described in detail, with the understanding that the features of the first tray assembly  2024   a  are fully applicable to the second tray assembly  2024   b  except for the noted differences. In addition, in  FIGS.  70 - 77   , only one representative first tray  2012   a  has been shown for ease of illustration and description, with the understanding that the features of that first tray  2012   a  are fully applicable to other first trays  2012   a  that might be mounted in a stacked arrangement therewith or to other second trays  2012   b  that might be mounted on the left side of the chassis  2010 . 
     Referring specifically now to  FIGS.  65 - 69   , the first and second tray assemblies  2024   a ,  2024   b  are shown outside of the chassis  2010 . As discussed for the previous embodiments of chassis and as will be discussed in further detail below, the two tray assemblies  2024 , when mounted together, capture a central PCB  2028  therebetween. The central PCB  2028  may electrically connect to indicators in the form of LEDs  2030  on both the front  2032  and the back  2034  of the chassis  2010  to communicate to a technician which tray  2012  should be accessed. As will be discussed in further detail, the LEDs  2030  may be carried by the removable trays  2012  and may be electrically connected to the central PCB  2028  when the trays  2012  are slidably mounted on the chassis  2010 . 
     All of the trays  2012  of both the first tray assembly  2024   a  and the second tray assembly  2024   b  are configured to be electrically connected to the central PCB  2028 . And, the central PCB  2028  is configured to be electrically connected to a main PCB or controller  2036  of the chassis  2010 , wherein the main PCB  2036  of the chassis  2010  is configured to communicate to a higher-level managed connectivity rack or frame  40 . 
     Referring still to  FIGS.  65 - 69   , the different parts of the first tray assembly  2024   a  are illustrated in an exploded configuration. The first tray assembly  2024   a  is formed from a center divider assembly  2027  that includes the central PCB  2028  and a pair of mounting blocks  2042  that capture the central PCB  2028  thereinbetween. The first tray assembly  2024   a  also includes the first tray  2012   a , an end support  2044 , the main PCB  2036 , and a backplane PCB  2066  that are mounted to the end support  2044 . As noted above and as will be described in further detail below, a flexible circuit in the form of a ribbon cable  2046  provides an electrical connection between the central PCB  2028  of the chassis  2010  and a tray PCB  2048  located on the tray  2012 . Another PCB (i.e., the top PCB)  2050  provides the connection between the central PCB  2028  and a backplane PCB  2066 . The main PCB or controller  2036  of the chassis  2010  is connected to the backplane PCB  2066  via card-edge-style connections. The top PCB  2050  is mounted to a mounting panel  2007 , the mounting panel  2007  configured to mount the top PCB  2050  to the top chassis cover  2018  of the chassis  2010 . The top PCB  2050 , via the central PCB  2028 , can connect both the first and second tray assemblies  2024   a ,  2024   b  to the main PCB  2036 . 
       FIG.  65    illustrates the chassis  2010  with the trays  2012  shown exploded off the chassis  2010 .  FIG.  66    illustrates the chassis  2010  with the ends supports  2044  and the center divider assembly  2027  of the chassis  2010  shown exploded off the chassis  2010 .  FIG.  67    illustrates the center divider assembly  2027  of the chassis  2010  in an exploded configuration.  FIG.  68    illustrates the right end support  2044  of the chassis  2010  in an exploded configuration, the right end support  2044  configured to house the main controller or PCB  2036  of the chassis  2010 .  FIG.  69    is a side view of the removable end cap  2064  of the right end support  2044  of the chassis  2010 . 
     Still referring to  FIGS.  65 - 69   , the right and left mounting blocks  2042  are configured for capturing the central PCB  2028  and mounting the central PCB  2028  and the center divider assembly  2027  to the chassis  2010 . The mounting blocks  2042  define fastener openings  2054  that are aligned with fastener openings  2056  of the central PCB  2028  for mounting the central PCB  2028  to the blocks  2042 . The mounting blocks  2042  also define fastener openings  2055  that are configured to align with fastener openings of the top chassis cover  2018  for mounting the center divider assembly  2027  to the chassis  2010 . 
     As will be discussed in further detail, each tray  2012  is configured to be slidably captured between the mounting block  2042  and the end support  2044  of the tray assembly  2024 . For the first tray assembly  2024   a , for example, the end support  2044  defines fastener openings  2060  for mounting to the top chassis cover  2018  and the bottom plate  2014 . The right end support  2044  is also configured to capture the main PCB  2036  and the backplane PCB  2066  against the right sidewall  2016  of the chassis  2010 , wherein the right sidewall  2016  is also fastened to the top chassis cover  2018 . The right end support  2044  defines a channel  2062  for housing the main PCB  2036  and the backplane PCB  2066 . As shown in  FIG.  68    and as will be discussed in further detail, the main PCB  2036  may be slidably loaded into the channel  2062  of the right end support  2044 . The main PCB  2036  is accessible to a technician by removing a front end cap  2064  of the end support  2044 . The main controller  2036  may use a card-edge-style connection  2017  at its opposite rear end to connect to the backplane PCB  2066  and eventually to the top PCB  2050  that is mounted to the chassis top cover  2018  via the mounting panel  2007 . As in the previous embodiments discussed, it should be noted that in the depicted embodiment of the chassis  2010 , since both tray assemblies  2024  are being connected through the central PCB  2028 , only one end support  2044  (i.e., the right end support) of the first tray assembly  2024   a  defines a channel  2062  for supporting the main controller  2036  and the backplane PCB  2066 , wherein the end support  2044  of the second tray assembly  2024   b  is not shown as housing a main PCB  2036  or backplane PCB  2066 . This configuration may be modified depending upon the orientation of the chassis  2010  within a given rack  40 . 
     Still referring to  FIG.  67   , the right mounting block  2042  defines channels  2078  for slidably receiving portions of the first tray assembly  2024   a  and the left mounting block  2042 , similarly defines channels  2078  for receiving portions of the second tray assembly  2024   b.    
     The left mounting block  2042  defines three lock levers  2019  at the front end thereof, one for each tray  2012 . The right mounting block  2042  defines three lock levers  2019  at the rear end thereof, one for each tray  2012 . As will be discussed in further detail below, the lock levers  2019  are configured to cooperate with portions of the trays  2012  in locking the trays  2012  with respect to the center divider assembly  2027 . When the center divider assembly  2027  has been formed with the central PCB  2028  captured between the mounting blocks  2042 , the lock levers  2019  of the left mounting block  2042  cooperate with the right trays  2012   a  in locking the trays  2012   a  against slidable movement with respect to the chassis  2010 . The lock levers  2019  of the right mounting block  2042  cooperate with the left trays  2012   b  in locking the trays  2012   b  against slidable movement with respect to the chassis  2010 . As discussed before, the chassis  2010  is configured such that the right trays  2012   a  are only removable from the front end  2032  of the chassis  2010  and the left trays  2012   b  are only removable from the rear end  2034  of the chassis  2010 . As will be discussed in further detail below, the lock levers  2019  have to be pivoted away from the center divider assembly  2027  before the trays  2012  can be slidably removed from the chassis  2010 . 
     Referring now to  FIGS.  70 - 78   , each tray  2012  of each tray assembly  2024  defines a main connection portion  2070 , a center mounting portion  2072 , a side mounting portion  2074 , and a cable management portion  2076 . Each tray  2012  also defines a slide assembly  2021  that is formed from a center rail  2023  that is configured to slide with respect to a mounting rail  2025 . As shown specifically in the exploded view in  FIG.  72   , the mounting rail  2025  defines a dovetail portion  2029  that is slidably captured against the center rail  2023  by a top cover  2031  of the center rail  2023 . The mounting rail  2025  also defines a gear rack  2033 , the purpose of which will be discussed in further detail below. 
     The center mounting portion  2072  of the tray  2012  is also configured for slidable coupling to the center rail  2023  of the slide assembly  2021 . The center mounting portion  2072  of the tray  2012  also defines a dovetail profile  2035  that is slidably captured against the center rail  2023  by the top cover  2031  of the center rail  2023 . The center mounting portion  2072  of the tray  2012  also defines a gear rack  2037 , the purpose of which will be discussed in further detail below. 
     The side mounting portion  2074  of the tray  2012  is configured for slidable coupling to an end support  2044  of the tray assembly  2024  that is located generally close to one of the sides of the chassis  2010 . 
     As noted previously, both the mounting block  2042  and the end support  2044  include longitudinally extending channels provided in a stacked arrangement. The channels  2078  of the mounting block  2042  are configured to slidably receive the mounting rail  2025  of the slide assembly  2021  of each tray  2012 . The lock levers  2019  of the mounting blocks  2042  are configured to fix the mounting rails  2025  to the mounting blocks  2042  with a snap fit interlock. In this manner, the mounting rail  2025  of the slide assembly  2021  is stationarily fixed with respect to the mounting block  2042 , thus, to the chassis  2010 . The center rail  2023  slides with respect to the mounting rail  2025 . And, the tray  2012  slides with respect to the center rail  2023 , at twice the speed of the center rail  2023  relative to the stationary mounting rail  2025  due to a gear arrangement, as will be discussed. 
     The channels  2080  of the end support  2044  are configured to receive the side mounting portion  2074  of each tray  2012  for supporting the slidable movement of the tray  2012 . 
     Referring now to the interaction between the side mounting portions  2074  of the trays  2012  and the channels  2080  of the end support  2044 , the side mounting portions  2074  and the channels  2080  of the end support  2044  might also define matching dovetail configurations for providing slidable movement and preventing lateral separation. Other types of support structures may also be used for slidable movement such as shelf type of alignment and support structures. 
     Regarding the interaction between the center mounting portions  2072  of the trays  2012  and the center rails  2023  of the slide assemblies  2021 , as discussed above, the center mounting portion  2072  of the tray also defines a dovetail profile  2035  that is slidably captured against the center rail  2023  by the top cover  2031  of the center rail  2023 . 
     Referring now to  FIGS.  74  and  74 A , the mounting rail  2025  is illustrated in isolation. As discussed above, the mounting rail  2025  is the portion of the slide assembly  2021  that is configured to be fixedly mounted to the mounting block  2042 . The mounting rail  2025  is the portion that needs to be removed from the channels  2078  of the mounting block  2042  in removing the entire tray  2012  and the slide assembly  2021  thereof from the chassis  2010 . Otherwise, with the mounting rail  2025  fixed in place with respect to the mounting block  2042 , each tray  2012  is still free to slide via the slide assembly  2021 , without being removed from the chassis  2010 . 
     Referring to the mounting rail  2025  of one of the first trays  2012   a , the mounting rail  2025  defines a dovetail configuration  2041  on the leftmost wall  2043  of the mounting rail  2025  for slidable insertion into one of the channels  2078  of the mounting block  2042 . As discussed above, the rightmost wall  2045  of the mounting rail  2025  also defines a dovetail configuration  2029  for allowing the center rail  2023  to slide with respect to the mounting rail  2025 . The gear rack  2033  also defined on the rightmost wall  2045  of the mounting rail  2025  is configured to interact with first and second gear wheels  2051  that are positioned on the center rail  2023 . 
     As the center rail  2023  slides with respect to the mounting rail  2025 , the gear teeth  2053  of the gear wheels  2051  cause the gear wheels  2051  to spin as they interact with the gear rack  2033  of the mounting rail  2025 . As the gear wheels  2051  spin, the wheels  2051  also interact with the gear rack  2037  that is found on the center mounting portion  2072  of the tray  2012 . Thus, when the center rail  2023  slides with respect to the stationary mounting rail  2025 , the tray  2012  slides with respect to the center rail  2023 , at twice the speed of the center rail  2023  relative to the stationary mounting rail  2025  due to the gear arrangement. 
     Still referring to  FIGS.  74  and  74 A , the mounting rail  2025  defines an LED mount  2055  at a front end thereof. The LED mount  2055  is configured to house a micro slide PCB  2057  that is provided with two LEDs  2030 , one on each side thereof. The LEDs  2030  can be seen through a pair of transparent lenses  2059  provided at the front of the LED mount  2055 . The micro slide PCB  2057  is captured within a PCB pocket  2061  of the LED mount  2055  with a cover  2063 . The rear end of the micro slide PCB  2057  defines an edge connection portion  2065  and receives a card-edge-style connector  2067 . The card-edge-style connector  2067  at the back end of the micro slide PCB  2057  is configured to electrically connect to one of the front extensions  2069  defined on the central PCB  2028 . The front extension  2069  of the central PCB  2028  extends through a slot  2071  located at the rear end of the LED mount  2055  to electrically connect to the micro slide PCB  2057  via the card edge connector  2067 . 
     As shown in  FIG.  74 A , the micro slide PCB  2057  electrically ties the tray  2012  to the central PCB  2028  via a flexible circuit in the form of a ribbon cable  2046 . The ribbon cable  2046  is configured to be connected to the micro slide PCB  2057  and enters into the PCB pocket  2061  via a side entrance  2073  of the LED mount  2055 . 
     Referring now to  FIGS.  72 ,  74 , and  74 A , the flexible circuit  2046  extends through the mounting rail  2025 . The mounting rail  2025  defines a flex pocket  2075  that runs longitudinally along the mounting rail  2025  and houses the flexible circuit  2046 . Toward the rear end of the mounting rail  2025 , the mounting rail  2025  defines a slot  2077  for directing the flexible circuit  2046  out of the flex pocket  2075  into the center rail  2023  as will be discussed in further detail below. 
     As noted above, the mounting rail  2025  is the portion of the slide assembly  2021  that is configured to be stationarily fixed with respect to the mounting block  2042  of the center divider assembly  2027 . 
     As discussed previously, the mounting block  2042  to the left of the central PCB  2028  defines three lock levers  2019 . The lock levers  2019  of the mounting blocks  2042  are configured to fix the mounting rails  2025  to the mounting blocks  2042  with a snap fit interlock once the mounting rails  2025  have been slidably inserted into the channels  2078  of the mounting blocks  2042 . As shown in  FIG.  65   , each LED mount  2055  defines an exterior lock detent  2079 . The lock detents  2079  flexibly receive the lock levers  2019  with a snap fit. If an entire tray  2012  needs to be removed from the chassis  2010 , the lock levers  2019  are pivoted away from the detents  2079  until they clear the detents  2079 . Once the lock levers  2019  clear the detents  2079 , the entire tray  2012  can be slidably removed from the chassis  2010 . 
     Referring now back to  FIGS.  72 - 73   , as noted above, the center rail  2023  receives the mounting rail  2025  on the left side of the center rail  2023  and the center mounting portion  2072  of the tray  2012  at the right side of the center rail  2023 . The center rail  2023  slides with respect to the mounting rail  2025  and also causes the tray  2012  to slide with respect to the center rail  2023  due to the gear wheels  2051  that are located within the center rail  2023 . The gear wheels  2051 , the rightmost wall  2045  of the mounting rail  2025  and the dovetail profile  2035  of the center mounting portion  2072  of the tray  2012  are captured with respect to the center rail  2023  via the top cover  2031 . The top cover  2031  is fastened to the center rail  2023  via fasteners  2081  that are inserted into fastener mounts  2083 . The fastener mounts  2083  are located on a divider wall  2085  that is located within the center rail  2023 . 
     The first and second gear wheels  2051   a ,  2051   b  are positioned within wheel pockets  2087  formed within the divider wall  2085  of the center rail  2023 . The gear wheels  2051  rotate freely once captured by the top cover  2031 . Each gear wheel  2051  defines a lower portion having the gear teeth  2053  and an upper portion that acts as a ribbon cable guide or pulley  2089 . 
     As shown in  FIG.  73   , once the flexible circuit in the form of the ribbon cable  2046  exits the center mounting portion  2072  of the tray  2012  and enters the center rail  2023 , the flexible circuit  2046  runs toward the front of the center rail  2023  and is positioned between the center mounting portion  2072  of the tray  2012  and the right side of the divider wall  2085  of the center rail. 
     Once lead around the first gear wheel  2051   a , the flex circuit  2046  is directed toward the rear of the center rail  2023  and is positioned at the left side of the divider wall  2085  (between the divider wall  2085  and the rightmost wall  2045  of the mounting rail  2025  (please see  FIG.  73   ). As shown in  FIG.  72   , the pocket  2087  that receives the gear wheel  2051  defines a notch  2091  that allows the ribbon cable  2046  to pass from the right side of the divider wall  2085  to the left side of the divider wall  2085 . 
     In this manner, as shown in the top view of  FIG.  73   , as the tray  2012  is moved back and forth with respect to the chassis  2010  via the slide assembly  2021 , any slack within the ribbon cable  2046  is taken up by the first gear wheel  2051   a , which acts as a pulley for the ribbon cable  2046 . 
     The portion of the flexible circuit  2046  that resides within the flex pocket  2087  of the mounting rail  2025  remains generally stationary while the portions of the flexible circuit  2046  that are located at both sides of the divider wall  2085  of the center rail  2023  move back and forth as the tray  2012  moves back and forth. 
     As noted previously, the mounting rail  2025  of the slide assembly  2021  is stationarily fixed with respect to the mounting block  2042 , thus, to the chassis  2010 . The center rail  2023  slides with respect to the mounting rail  2025 . And, the tray  2012  slides with respect to the center rail  2023 , at twice the speed of the center rail  2023  relative to the stationary mounting rail  2025  due to the gear arrangement. 
     When the tray  2012  is in a fully pulled-out position, a pivotable slide lever  2093  is used to lock and release the tray  2012 . As shown in  FIGS.  72  and  73   , the center rail  2025  defines a lever housing  2095  at a front end thereof. The lever housing  2095  houses the slide lever  2093 . The slide lever  2093  defines a catch portion  2097  and a finger grip portion  2099 . The slide lever  2093  is pivotally coupled to the lever housing  2095  via a pivot hinge  2101  defined by a pivot pin  2103 . The slide lever  2093  is laterally biased by a spring  2105  that is within the lever housing  2095 . As the lever  2093  is pushed laterally toward the left using the finger grip portion  2099 , the spring  2105  is loaded and biases the lever  2093  back toward the right. The catch portion  2097  is configured to interact with an extension latch  2107  defined on the center mounting portion  2072  of the tray  2012 . 
     When the tray  2012  is fully pulled out, the extension latch  2107  locks with the catch portion  2097  of the slide lever  2093 . In order to free the tray  2012  and allow it to slide back, the finger grip portion  2099  of the slide lever  2093  is pushed, against the bias of the spring  2105 , and the catch portion  2097  is released from the extension latch  2107  of the tray  2012 . 
     Once the tray  2012  starts sliding into the chassis  2010 , the tray also makes temporary stops at discrete positions along its travel path. For this purpose, the center rail  2023  defines stop detents  2109  positioned at discrete locations along the center rail  2023 . The detents  2109  cooperate with a flexible position latch  2111  located on the center mounting portion  2072  of the tray  2012 . The position latch  2111  is located underneath the extension latch  2107  and defines a round profile to facilitate entrance into and removal from the stop detents  2109 . 
     It should be noted that the center rail  2023  is configured with similar features at both the front end and the rear end, such as the slide lever  2093 , so that trays  2012  can be accessed and slid from both ends of the chassis  2010  in either the forward direction or the rearward direction. 
     Referring now to  FIGS.  119 - 121   , another version of a slide assembly  5021  for mounting a tray such as the tray  2012  to a chassis such as chassis  2010  is illustrated. The slide assembly  5021  includes features similar to slide assembly  2021  of  FIGS.  72 - 73    but also includes certain differences, which will be discussed in further detail. 
     Still referring to  FIGS.  119 - 121   , the slide assembly  5021  includes a further locking arrangement for locking a tray such as tray  2012  at the center position within a chassis. 
     Similar to slide assembly  2021 , slide assembly  5021  defines a mounting rail  5025  that is stationarily fixed with respect to the mounting block  2042 , thus, to the chassis  2010 . A center rail  5023  of the slide assembly slides with respect to the mounting rail  5025 . And, a tray such as the tray  2012  that is mounted using the slide assembly  5021  slides with respect to the center rail  5023 , at twice the speed of the center rail  5023  relative to the stationary mounting rail  5025  due to the gear arrangement. 
     The slide assembly  5021  includes a pivotable slide lever  5093  similar to slide lever  2093  of slide assembly  2021 . When a tray is in a fully pulled-out position, the pivotable slide lever  5093  is used to lock and release the tray. As shown in  FIGS.  119 ,  119 A,  120 ,  120 A, and  120 B , the center rail  5023  defines a lever housing  5095  at a front end thereof. The lever housing  5095  houses the slide lever  5093 . The slide lever  5093  defines a catch portion  5097  and a finger grip portion  5099 . The slide lever  5093  is pivotally coupled to the lever housing  5095  via a pivot hinge  5101  defined by a pivot pin  5103 . The slide lever  5093  is laterally biased by a spring  5105  that is within the lever housing  5095 . As the lever  5093  is pushed laterally toward the left using the finger grip portion  5099 , the spring  5105  is loaded and biases the lever  5093  back toward the right. The catch portion  5097  is configured to interact with an extension latch such as the extension latch  2107  defined on the center mounting portion  2072  of the tray  2012 . 
     When a tray such as tray  2012  is fully pulled out, the extension latch  2107  locks with the catch portion  5097  of the slide lever  5093 . In order to free the tray  2012  and allow it to slide back, the finger grip portion  5099  of the slide lever  5093  is pushed, against the bias of the spring  5105 , and the catch portion  5097  is released from the extension latch  2107  of the tray  2012 . 
     Once the tray  2012  starts sliding into the chassis  2010 , the tray also makes temporary stops at discrete positions along its travel path. For this purpose, the center rail  5023  defines stop detents  5109  positioned at discrete locations along the center rail  5023 . The detents  5109  cooperate with a flexible position latch  2111  located on the center mounting portion  2072  of the tray  2012 . The position latch  2111  is located underneath the extension latch  2107  and defines a round profile to facilitate entrance into and removal from the stop detents  5109 . 
     The center rail  5023  is configured with similar features at both the front end and the rear end, such as the slide lever  5093 , so that trays such as trays  2012  can be accessed and slid from both ends of the chassis  2010  in either the forward direction or the rearward direction. 
     As noted above, in addition to the stop detents  5109  positioned at discrete locations along the center rail  5023 , the slide assembly  5021  includes a further locking feature for locking a tray such as tray  2012  at the center position within a chassis such as chassis  2010 . 
     As shown in  FIGS.  119 - 121   , the slide assembly  5021  includes a pivot lever  5111  that is pivotally connected to the slide lever  5093 . The pivot lever  5111  includes a second catch portion  5113  that is configured to fit within a detent  5115  located on the mounting rail  5025  of the slide assembly  5021 . When the tray  2012  is positioned at the central position within the chassis  2010 , the second catch portion  5113  is positioned within the detent  5115 . Since the slide lever  5093  is laterally biased by the spring  5105  toward the right, the pivot lever  5111  is biased to pivot in a counter-clockwise direction and the second catch portion  5113  sits within the detent  5115  under the bias force of the spring  5105 . 
     When the tray  2012  needs to be moved from the central position and pulled forwardly, the lever  5093  is pushed laterally toward the left using the finger grip portion  5099  and the spring  5105  is compressed. Pushing the lever  5093  laterally leftwardly pivots the lever  5111  in a clockwise direction and frees the second catch portion  5113  from the detent  5115 , allowing the tray to now be slid forwardly. 
     It should be noted that the center rail  5023  is configured with similar features at both the front end and the rear end such as the pivot lever  5111 , so that trays  2012  can be accessed and slid from both ends of the chassis  2010  in either the forward direction or the rearward direction as they are released from a central position within the chassis  2010 . 
     As shown in the close-up view in  FIG.  120 A , the second catch portion  5113  and the detent  5115  both include complementary angled faces  5117 ,  5119  such that if the tray  2012  is pulled from the rear end of the chassis  2010 , the angled face  5117  of the second catch portion  5113  at the front of the slide assembly can automatically clear the detent  5115  as the center rail  5023  is moved with respect to the mounting rail  5025 . 
     When a tray  2012  is not at the central position, the second catch portions  5113  of the pivot levers  5111  are either not in contact with or simply ride along the surface of the mounting rail  5025  and are not used in locking the tray. Please see  FIGS.  121 ,  121 A, and  121 B . When the tray  2012  is at a forward or backward position as shown in  FIGS.  121 ,  121 A, and  121 B , only the slide lever  5093  is used in locking the tray  2012 . 
       FIGS.  120 ,  120 A, and  120 B  illustrate a tray such as the tray  2012  locked in a central position within the chassis  2010 , wherein both the front and rear pivot levers  5111  are being used to lock the tray. When moving the tray from the central position either forwardly or rearwardly, the finger grip portion  5099  of the corresponding slide lever  5093  (either front or back) has to be pressed to move the pivot lever  5111  attached to that slide lever  5093  in freeing the tray. 
     Thus, the slide assembly  5021  includes features that allow locking of the trays, not only in the forward and rearward positions, but also at the central position, wherein the trays will not be accidentally moved from their neutral position without engaging, once again, the finger grip portions  5099  of the slide levers  5093 . 
     Referring now back to  FIG.  75   , the main connection portion  2070  of the tray  2012  is located between the center mounting portion  2072  and the side mounting portion  2074  and is configured to define connection locations for the tray  2012 . By stacking a plurality of the trays  2012  on a distribution chassis  2010 , density of connections for fiber optic transmission can be increased and the slidability of the trays  2012  in either the front direction or the rear direction provides for easy access at both the front or the rear of the distribution chassis  2010 . 
     As shown in  FIG.  75   , the depicted version of the main connection portion  2070  of the tray  2012  includes a mount  2116  for mounting fiber optic adapters which define the fiber optic connection locations in the present embodiment of the tray  2012 . Specifically, in the tray  2012  shown and described in the present application, the fiber optic connection locations may be defined by adapters having an LC type footprint. In the depicted embodiments, twenty-four LC adapters may be mounted to the mount  2116  via a snap-fit connection defined on the mount  2116 . In the high density distribution chassis  2010  shown in the present disclosure, six slidable trays  2012  may be mounted on a 1RU of rack space, providing 144 LC connections as noted above. 
     As noted earlier, other standards of fiber optic adapters (such as SC or MPO adapters) can be mounted to the mount  2116 . Fiber optic adapters are only one type of fiber optic equipment that provides connection locations for the tray  2012  and the tray  2012  can be used with other types of fiber optic equipment. For example, equipment such as fiber optic splitters, couplers, multiplexers/demultiplexers, or other types of equipment wherein cables may be routed away from the connection locations may be housed on the main connection portion  2070 . 
     If fiber optic adapters are used, the connection locations may be defined by adapters individually mounted in the mount  2116  or may be defined by adapter block assemblies that include integrally formed adapters in block form, as shown in the previously depicted embodiments. In other embodiments, the connection locations may be in the form of a cassette that may include fiber optic adapters on one side wherein the opposite side may have a multi-fiber connector or a cable extending outwardly therefrom, with optical fibers normally housed within such a cassette. 
     Examples of devices that may define the connection locations such as the adapter block assemblies or cassettes are illustrated and described in further detail in U.S. Pat. Nos. 9,423,570; 9,285,552; and 9,379,501, which have been incorporated by reference in their entireties. 
     As noted previously, the chassis or panels  2010  may be available in 1-rack-unit (1RU) and 4-rack-unit (4RU) sizes. The 1RU panels may house 144 mated LC connector pairs, 72 SC connector pairs or 48 MPO connector pairs. The 4RU panels may house four times the number of connections as the 1RU units with the same functionality. 
     Within each panel  2010  and within each tray  2012 , the connection locations may be accessible from both the front  2032  and the back  2034  of the panel  2010 . An adapter block assembly may be installed on a sliding tray  2012  such that it resides toward the center portion of the panel  2010 . The trays  2012  can be slid forwardly or rearwardly to access the front connections or the rear connections of an adapter block assembly. 
     Cable management is an important aspect of a high density distribution panel or frame when managing a high density of cables extending from the front and rear ends of the adapter block assemblies that may be mounted on the trays  2012 . 
     As discussed above, each tray  2012  is configured to include a cable management portion  2076  for managing cables from the connection locations to and away from the chassis  2010  both for the cables extending from the front ports of the adapters and from the rear ports of the adapters. The cable management portions  2076  of the trays  2012  are configured such that they accommodate any cable slack during the forward and rearward slidable movements of the trays  2012 , while maintaining minimum bend radius requirements of the cables. Also, the cable management portions  2076  of the trays  2012  are designed to keep the same length of cabling from the connection locations to the exterior of the chassis  2010  so as to prevent any pulling or pinching of the cables and to limit the need for excess slack cabling. 
     The cable management portion  2076  of each tray  2012  may be defined by a front cable management portion  2076   a  and a rear cable management portion  2076   b . It should be noted that the front and rear cable management portions  2076   a ,  2076   b  are similar in configuration and only the front cable management portion  2076   a  will be discussed herein for ease of description, with the understanding that all of the inventive features of the front cable management portion  2076   a  of a given tray  2012  are fully applicable to the rear cable management portion  2076   b.    
     Referring now to  FIGS.  71  and  76 - 78   , the front cable management portion  2076   a  is defined by a radius limiter  2124  that is located adjacent the side mounting portion  2074  of the tray  2012  and a link arm assembly  2126  made up of five cable management link arms  2128 , which are attached between the radius limiter  2124  and the front of the end support  2044  of the tray assembly  2024 . The side mounting portion  2074  of the tray  2012  also includes removable cable management fingers  2144  that are snap fit over the radius limiters  2124  to manage the cables therearound. 
     In the depicted embodiment, the cable management portion  2076  of the trays  2012  are configured for top and side loading of the cables thereinto. As shown in  FIGS.  71  and  76 - 78   , the radius limiter  2124  defines a generally curved cable channel  2142  with the removably-mounted inwardly extending cable management fingers  2144  for retaining cables once therein. In such an example, the cables can be top loaded into the radius limiter  2124  as they extend from the connection locations. 
     The link arms  2128  are configured to swing forwardly and out of the way for access to the front of the adapter block assembly  2120  when the tray  2012  is pulled forwardly. When a technician is done accessing and/or loading the front connectors, the tray  2012  is pushed back to its original closed location. 
     The link arms  2128  are defined by five link arms that are pivotally coupled with respect to each other so as to define a limited pivotal movement therebetween. All of the link arms  128  include snap-fit coupling features defined, for example, by cylindrical tabs  2148  on a first male end  2150  and cylindrical receptacles  2152  on an opposite second female end  2154  for providing the pivotal movement. 
     The five link arms include a first link arm  2128   a  that is directly pivotally coupled to the front of the end support  2044  of the tray assembly  2024 . The first link arm  2128   a  is pivotally connected to the end support  2044  such that it can move between a transverse position when the tray  2012  is closed to a longitudinal orientation when the tray  2012  is fully open, similar to the view shown in  FIG.  22   . A contact surface  2146  defined on the first link arm  2128   a  prevents further movement of the first link arm  2128   a  with respect to the end support  2044 . The next link arm  2128   b  of the link arm assembly  2126  is configured to house an extension spring  2113  that is configured to bias the link arm assembly  2126  and thus the tray  2012  to a closed position, as will be discussed in further detail below. 
     The next two link arms  2128   c  are configured to have the same shape as each other. Each of the similar link arms  2128   c  are coupled back to back from the second link arm  2128   b  toward a fifth link arm  2128   d  that is connected to the radius limiter  2124  of each tray  2012 . Each of the link arms  2128 , as in the first link arm  2128   a , defines contact surfaces  2156  such that they are limited in their pivotal movement with respect to each other. For example, the link arm  2128   b  that is directly coupled to the first link arm  2128   a  might define a contact surface  2156  to prevent further pivotal movement with respect thereto when the tray  2012  is fully open. Each of the link arms  2128 , including the first link arm  2128   a , is designed such that regardless of position of the moving tray  2012 , the cables contained therewithin will not violate the minimum bend radius requirements. 
     Referring now specifically to  FIGS.  76 - 78   , exploded views of a right link arm assembly  2126  and a left link assembly  2126  are shown, illustrating the extension springs  2113  that are configured to bias the link arm assemblies  2126  and thus the trays  2012  to a closed position. In the link arm assembly  2126 , the link arm  2128   b  is configured to support a slidable spring mount  2115 . A spring mount cover  2117  captures the slidable spring mount  2115  against the link arm  2128   b  and snaps onto the link arm  2128   b  with snap-fit structures  2119 . The spring mount cover  2117  defines a track  2121  along which the slidable spring mount  2115  can slide. The extension spring  2113  is mounted between a mount pin  2123  defined on the slidable spring mount  2115  and a mount pin  2125  defined on the spring mount cover  2117  (please refer to  FIG.  78   ). As the slidable spring mount  2115  slides away from the pin  2125  of the spring mount cover  2117 , the extension spring  2113  is extended under a load. When at an extended position, the spring  2113  biases the slidable spring mount  2115  toward its initial position. The slidable spring mount  2115  is linked to one of the link arms  2128   c  with a spring mount link  2129 . The spring mount link  2129  defines male snap-fit structures in the form of pins  2131  that are received into female snap-fit structures in the form of receptacles  2133  that are provided both on the slidable spring mount  2115  and the link arm  2128   c.    
     In this manner, when the link arm  2128   b  and the link arm  2128   c  pivot relative to each other, the slidable spring mount  2115  is slidably moved via the spring mount link  2129 . As the slidable spring mount  2115  is moved with respect to the spring mount cover  2117  along its track  2121 , the spring  2113  extends and is loaded with a biasing force. Thus, when the link arms  2128   b  and  2128   c  are pivoted to an angle that is larger than 90 degrees, the spring  2113  biases the link arms  2128   b  and  2128   c  to a generally 90-degree, right angle position and starts to pull the entire link arm assembly  2126  back into the tray  2012 . The initial pull provided by the extension spring  2113  facilitates moving the link arm assembly  2126  and the tray  2012  back into the chassis  2010 . Although only one of the link arms  2128   b  is used with the extension spring  2113 , the two link arms  2128   b  are manufactured with the same features, including receptacles  2133  for receiving an end of the spring mount link  2129 , for manufacturing efficiency purposes. Also, although only one of the link arm assemblies  2126  has been described herein with respect to having an extension spring  2113 , it should be noted that an extension spring  2113  is used on all four corners of the chassis  2010  to facilitate closing of the trays. 
     Referring now to  FIGS.  87 - 95   , another feature that facilitates the closing and opening of the link arm assemblies is illustrated. This feature, as illustrated in  FIGS.  87 - 95   , includes a compression spring assembly  4115  that is configured to bias a first link arm away from the adjacent link arm attached thereto. It should be noted that the compression spring assembly  4115  is shown with an alternative embodiment of a link assembly  4126  that has features similar to the link assemblies  2126  discussed above. The link assembly  4126 , which will be discussed in further detail below, includes certain additional features to that of the link assembly  2126 . 
     Still referring to  FIGS.  87 - 95   , the compression spring assembly  4115  is configured bias the first link arm  4128   a  away from the link arm  4128   b  so as to provide a generally 90-degree angle between the two arms  4128   a ,  4128   b . The biasing provided by the compression spring assembly  4115  facilitates closing and opening of the link arm assembly  4126 . During opening, the link arm  4128   b  applies a contact force on the spring assembly  4115 , which in turn applies a force on the first link arm  4128   a  to spread the two link arms apart to generally a 90-degree position to help establish a smooth opening motion for the arms  4128   a ,  4128   b . Similarly, during closing, the link arm  4128   a  applies a contact force on link arm  4128   b  through the compression spring assembly  4115  and forces the link arm  4128   b  away from link arm  4128   a  to start moving it in the closing direction. 
     As shown in the exploded view provided by  FIG.  89   , the compression spring assembly  4115  includes a slider  4117  that is mounted within a spring housing  4119 . The slider  4117  is biased away from the spring housing  4119  via a compression spring  4113  that is captured between the slider  4117  and the spring housing  4119 . The slider  4117  defines a pair of tabs  4121  that slide within opposing tracks  4123  provided in the spring housing  4119 . The slider  4117  is limited in its movement away from the spring housing  4119  due to stops  4125  formed at the ends of the tracks  4123 , which are contacted by the tabs  4121  of the slider  4117 . The slider  4117  and the spring housing  4119  include further guiding or keying features  4131 ,  4133  for slidably guiding the slider  4117  within the spring housing  4119 . The spring housing is shown in isolation in  FIGS.  90 - 92    and the slider is shown in isolation in  FIGS.  93 - 95   . 
     The spring housing  4119  includes snap-fit features  4127  for latching the spring housing  4119  to the first link arm  4128   a  as shown in  FIGS.  87 - 92   . The features provided on the first link arm  4128   a , such as snap-fit tabs  4129 , are some of the differences provided on the alternative version of the link assembly  4126  as compared to the link assembly  2126  discussed earlier. Certain other differences for the version of the link assembly  4126  will be discussed in further detail below. 
     Referring now back to  FIGS.  76 - 78   , according to one example embodiment, as shown in  FIGS.  76 - 78   , all of the link arms  2128  (and link arms  4128 ) may be designed for top and side loading of the cable, wherein cable management tabs  2158  might be located on the peripheral edges  2160 . 
     The first link arm  2128   a  that is directly attached to one of the end supports  2044  of the tray assembly  2024  may be designed to hold structures such as fanouts, which are devices that transition fiber from one high-fiber-count cable to multiple single-fiber-count cables. 
     The version of the link arm assembly  4126  that has features similar to link arm assembly  2126 , as shown in  FIGS.  96 - 118   , is illustrated with such features designed to hold equipment such as fanouts. The features for holding equipment such as fanouts are some of the other differences provided on the alternative version of the link assembly  4126  as compared to the link assembly  2126  discussed above. 
     Still referring to  FIGS.  96 - 118   , in the version of the link assembly  4126 , the first link arm  4128   a  includes features for holding different sized fanouts. In the depicted embodiment, the first link arm  4128   a  includes features for holding two different sized fanouts. 
     In  FIGS.  96 - 100   , the first link arm  4128   a  is shown with a pair of first fanouts  4141  (e.g., 2 mm fanouts). The link arm  4128   a  may be provided with bumps  4143  on the top and bottom walls  4145 ,  4147  of the link arm  4128   a  for accepting the first fanouts  4141  with a snap-fit interlock. The first fanouts  4141  define cavities or slots  4149  for receiving the bumps  4143  located on the top and bottom walls  4145 ,  4147  of the first link arm  4128   a . As shown in  FIGS.  96  and  97   , when the two fanouts  4141  are mounted, one is mounted at an angle to provide a space  4151  for cables  4153  that are fanned out from the rear fanout  4141 . The cables  4153  fanned out from the rear fanout  4141  are able to pass by the front fanout  4141  and are retained by cable management features  4160  defined by the periphery of the link arm  4128   a.    
     Referring now to  FIGS.  101 - 104   , the first link arm  4128   a  is shown with a pair of second fanouts  4161 . The second fanouts  4161  depicted are 900 micron fanouts and are sized smaller than the 2 mm first fanouts  4141  discussed above. In mounting the second fanouts  4161 , the first link arm  4128   a  utilizes a fanout holder  4155  that is configured to receive the second fanout  4161  with a snap-fit interlock and also latch to the first link arm  4128   a.    
     The holder  4155  and the second fanout  4161  are shown in an exploded configuration in  FIG.  105   . In  FIGS.  106 - 111   , the holder  4155  and the second fanout  4161  are shown in a coupled arrangement. The holder  4155  is shown in isolation in  FIGS.  112 - 118   . 
     As noted, the holder  4155  includes flexible cantilever arms  4157  both at the top and bottom sides of the holder  4155 . The cantilever arms  4157  include latching tabs  4159  that are configured to snap into detents  4162  provided on the top and bottom walls  4145 ,  4147  of the first link arm  4128   a . The holder  4155  also includes flexible holding tabs  4164  for mounting the second fanout  4161  to the holder  4155 . 
     Thus, with the use of a holder  4155 , the link arm  4128   a  is provided with features for accommodating two different types and sizes of fanouts. 
     Referring now back to  FIGS.  76 - 78   , in an example cable routing configuration, cables may lead from both the front and rear connection locations of a tray  2012  through the radius limiters  2124  and through each of the link arms  2128   d ,  2128   c ,  2128   b  in that order and finally through the first link arm  2128   a  before being directed out of the chassis  2010 . As noted above, the front link arm assembly  2126   a  and the rear link arm assembly  2126   b  are configured to move simultaneously together to manage the cable slack as the trays  2012  are pulled out from either direction. 
     Referring now to  FIGS.  70 ,  71 , and  71 A , the cable management portion  2076  of the trays  2012  may also include snap-on cable retainers  2005  located at the main connection portion of each tray  2012  that extend toward the front and the back of the trays. The cable retainers  2005  may include snap-fit features for coupling to a central divider portion  2164  of the trays  2012 . The cable retainers  2005  are configured to hold or retain cables extending from the connection locations toward the link arm assemblies  2126 . 
     Referring for example to  FIGS.  75 ,  79 , and  80   , as discussed for previous embodiments, in accordance with some aspects, certain types of adapters that are mounted to the trays  2012  in the form of adapter block assemblies may be configured to collect physical layer information from one or more fiber optic connectors received thereat. For example, certain types of adapters of the adapter block assemblies may include a body configured to hold one or more media reading interfaces that are configured to engage memory contacts on the fiber optic connectors. One or more media reading interfaces may be positioned in the adapter body. In certain implementations, the adapter body may define slots extending between an exterior of the adapter body and an internal passage in which the ferrules of the connectors are received. 
     Certain types of media reading interfaces may include one or more contact members that are positioned in the slots. A portion of each contact member may extend into a respective one of the passages to engage memory contacts on a fiber optic connector. Another portion of each contact member may also extend out of the slot to contact a circuit board that may be positioned on the adapter block assembly. As noted, portions of the tray  2012  and the chassis  2010  may define conductive paths that are configured to connect the media reading interfaces of the adapters with a main controller or PCB  2036  of the chassis  2010 , which can further communicate with a controller of the rack  40  that is housing the chassis  2010 . 
     The main controller  2036  of the chassis  2010  or the controller of the rack  40  may include or connect (e.g., over a network) to a processing unit that is configured to manage physical layer information obtained by the media reading interfaces. 
     According to the depicted example embodiment, on each tray  2012 , once a technician attaches an adapter block assembly using snap features on the tray  2012 , the adapter block assemblies may plug into the network as discussed above. For such managed panels  2010 , for example, the printed circuit boards of the adapter block assemblies may connect to the tray  2012  using multi-pin connectors  2162  on the tray  2012  as shown in  FIGS.  75  and  79   . The multi-pin connectors  2162  on the tray  12  may be attached to the flexible circuit formed by the ribbon cable  2046  that routes to the central PCB  2028  within the panel  2010 . As shown, the conductive pathway from the multi-pin connectors  2162  to the ribbon cable  2046  is provided by a printed circuit board  2048  that is located at the central divider portion  2164  of the tray  2012  and also by a portion  2045  of the flexible ribbon cable  2046  that is positioned horizontally along the rear side  2166  of the main connection portion  2070  of the tray  2012 . The printed circuit board  2048  and the horizontal portion  2045  of the ribbon cable  2046  are preferably mounted flush within recesses  2168  provided on the central divider  2164  and the rear side  2166  of the main connection portion  2070  of the tray  2012 . 
     A tray PCB cover  2001  may be snapped on to the tray to protect the printed circuit board  2048  and the horizontal portion  2045  of the ribbon cable  2046 , as shown in  FIGS.  71  and  71 A . 
     The portion  2045  of the flexible circuit or ribbon cable that is positioned horizontally along the rear side  2166  is provided with a twist to position it vertically as it passes from the center mounting portion  2072  of the tray  2012  to the slide assembly  2021 . The vertical portion  2047  of the ribbon cable passes through a slot  2135  located adjacent the rear end of the center mounting portion  2072  of the tray  2012  to the opposite side of the center mounting portion  2072  of the tray  2012 . As discussed previously, the portion  2047  of the ribbon cable  2046 , which is provided in a vertical orientation, may then be looped within the slide assembly  2021  of the tray  2012  as shown in  FIGS.  72 ,  73 , and  79   . The vertical portion  2047  of the ribbon cable  2046  is configured to move within the slide assembly  2021  to allow the tray  2012  to travel back and forth without disrupting the communication through the ribbon cable  2046  between the central PCB  2028  and tray PCB  2048 . 
     As shown in  FIG.  73   , once the ribbon cable  2046  exits the center mounting portion  2072  of the tray  2012  and enters the center rail  2023 , the ribbon cable  2046  runs toward the front of the center rail  2023  and is positioned between the center mounting portion  2072  of the tray  2012  and the right side of the divider wall  2085  of the center rail  2023 . Once lead around the first gear wheel  2051   a , the ribbon cable  2046  is directed toward the rear of the center rail  2023  and is positioned at the left side of the divider wall  2085  (between the divider wall  2085  and the rightmost wall  2045  of the mounting rail  2025  (please see  FIG.  73   ). As the tray  2012  is moved back and forth with respect to the chassis  2010  via the slide assembly  2021 , any slack within the ribbon cable  2046  is taken up by the first gear wheel  2051   a , which acts as a pulley for the ribbon cable  2046 . 
     The portion of the ribbon cable  2046  that resides within the flex pocket  2075  of the mounting rail  2025  remains generally stationary while the portions of the ribbon cable  2046  that are located at both sides of the divider wall  2085  of the center rail  2023  move back and forth as the tray  2012  moves back and forth. As discussed previously, an end  2172  of the ribbon cable  2046  that is within the flex pocket  2075  connects to the micro slide PCB  2057  housed within the LED mount  2055  of the mounting rail  2025  of the slide assembly  2021 . When a tray  2012  is slidably mounted to the mounting block  2042  and is locked in via the lock lever  2019 , the tray  2012  establishes electrical communication with the central PCB  2028  via card-edge-style connections between the micro slide PCB  2057  and the front extensions  2069  of the central PCB  2028 . 
     As noted above, the micro slide PCB&#39;s  2057  of the slide assemblies  2021  may use indicators such as LEDs  2030  on both the front  2032  and back  2034  of the panel  2010  to communicate to a technician which tray  2012  should be accessed. The central PCB  2028  then may connect to the main PCB or controller  2036  of the chassis  2010 , which is housed within the end support  2044  of the tray assembly  2024 . The connection is made via the top PCB  2050  that runs along the top cover  2018  of the panel  2010  into the end support  2044 . The top PCB  2050  is configured to extend to the backplane PCB  2066  located toward the rear of the channel  2062  via a card-edge-style connection. The main controller  2036  is accessible to the technician by removing a removable front end cap  2064  of the applicable end support  2044 . The main controller  2036  may also use a card-edge-style connection at its opposite rear end to connect to the backplane PCB  2066 , allowing the main controller  2036  to be a field-replaceable device. The main controller  2036  is configured to communicate to a higher-level managed connectivity rack or frame  40  via a connection on the side of the panel  2010 . The main controller  2036  of the panel  2010  may be powered via another connection on the side of the panel  2010 . 
     The right end support  2044  is shown in an exploded configuration in  FIG.  68    to illustrate the removability feature of the end cap  2064 . The end cap  2064  includes an end cap lever  2137  that needs to be pulled toward the front of the chassis  2010  when removing the end cap  2064 . The lever  2137  slides within an aperture  2139  defined by an end cap cover  2241  that is used to capture the lever  2137  against the end cap  2064 . The lever  2137  defines a pair of angled pin tracks  2141  that are configured to receive the pins  2143  of two opposing locking tabs  2145 . The locking tabs  2145  include tapered locking ends  2147  that are configured to snap into upper and lower notches  2149  defined on extensions  2151  provided on the end support  2044 . The tapered ends  2147  need to be cleared off the notches  2149  to pull the end cap  2064  forwardly and remove it from the end support  2044 . As shown in  FIG.  69   , when the lever  2137  is pulled toward the front  2032  of the chassis  2010 , the locking tabs  2145  are pulled toward the lever  2137 . The tapered ends  2147  that are snapped into the notches  2149  are pulled out of the notches  2149  due to the interaction of the pins  2143  and the tracks  2141  and the end cap  2064  can be removed from the end support  2044 . A spring  2153  biases the lever  2137  rearwardly, to keep the locking tabs  2145  in a locking position. When the lever  2137  is pulled forwardly, the lever  2137  is pulled against the bias of the spring  2153 . 
     Once the main controller  2036  has been inserted into the end support  2044 , the end cap  2064  can be slidably re-inserted onto the end support  2044 , with the extensions  2151  of the end support  2044  slidably fitting into guides  2155  defined on the end cap  2064 . The tapered ends  2147  of the locking tabs  2145  contact the extensions  2151  and eventually clear the extensions  2151  under the bias of the spring  2153  until they snap into the notches  2149  defined on the extensions  2151 . 
     It should be noted that in the depicted embodiment, only the front end cap  2064  of the right end support  2044  has been provided with features to make it removable. A similar end cap cover  2141  may be used on all four corners of the chassis  2010  for efficiency in manufacturing. 
     Although in the foregoing description, terms such as “top,” “bottom,” “front,” “back,” “right,” “left,” “upper,” and “lower” were used for ease of description and illustration, no restriction is intended by such use of the terms. The telecommunications devices described herein can be used in any orientation, depending upon the desired application. 
     Having described the preferred aspects and embodiments of the present invention, modifications and equivalents of the disclosed concepts may readily occur to one skilled in the art. However, it is intended that such modifications and equivalents be included within the scope of the claims which are appended hereto.