Patent Publication Number: US-8542972-B2

Title: Wavelength division multiplexing module

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 12/467,564, filed May 18, 2009, which is a continuation of application Ser. No. 11/975,905, filed Oct. 22, 2007, now U.S. Pat. No. 7,536,075, issued May 19, 2009, which applications are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present disclosure generally relates to fiber optic telecommunications equipment. More specifically, the present disclosure relates to fiber optic modules and chassis for holding fiber optic modules. 
     BACKGROUND 
     In fiber optic telecommunications systems, it is common for optical fibers of transmission cables to be split into multiple strands, either by optical splitting of a signal carried by a single stranded cable or by fanning out the individual fibers of a multi-strand cable. Further, when such systems are installed, it is known to provide excess capacity in the installations to support future growth and utilization of the fibers. Often in these installations, modules including splitters or fanouts are used to provide the connection between transmission fibers and customer fibers. To reduce the cost and complexity of the initial installation and still provide options for future expansion, a module mounting chassis capable of mounting multiple modules may be used in such an installation. 
     While the chassis may accept several modules, the initial installation may only include fewer modules mounted in the chassis, or enough to serve current needs. These chassis may be configured with limited access to one or more sides, or may be mounted in cramped locations. In addition, some of these chassis may be pre-configured with the maximum capacity of transmission cables to accommodate and link to modules which may be installed in the future. Since it is desirable to have access to components within the chassis for cleaning during the installation of a new module, some provision or feature of the chassis will desirably permit a user to access and clean the connectors of these pre-connectorized and pre-installed transmission cables. 
     It is also desirable for the chassis to be configured to ensure that modules are installed correctly and aligned with other components within the chassis to mate with the pre-connectorized and pre-installed transmission cables. 
     In fiber-optic communications, it is also common for optical signals of transmission cables to be multiplexed. Wavelength division multiplexing (WDM) is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths of laser light to carry different signals. This allows for a multiplication in capacity, in addition to making it possible to perform bidirectional communications over one strand of fiber. 
     A WDM system uses a multiplexer at the transmitter to join signals together and a demultiplexer at the receiver to split them apart. With the right type of fiber, it is possible to have a device that does both simultaneously, and can function as an optical add-drop multiplexer. WDM systems allow expansion of the capacity of the network without laying more fiber. 
     WDM systems are divided in different wavelength patterns: 1) conventional WDM; 2) dense WDM (DWDM); and 3) coarse WDM (CWDM). Conventional WDM systems may provide up to 16 channels in the 3rd transmission window (C-band) of silica fibers around 1550 nm with a channel spacing of 100 GHz. DWDM may use the same transmission window but with less channel spacing enabling up to 31 channels with 50 GHz spacing and 62 channels with 25 GHz spacing, sometimes called ultra dense WDM. CWDM in contrast to conventional WDM and DWDM uses increased channel spacing to allow less sophisticated and thus less expensive transceiver designs. WDM, DWDM and CWDM are based on the same concept of using multiple wavelengths of light on a single fiber, but differ in the spacing of the wavelengths, number of channels, and the ability to amplify the multiplexed signals in the optical space. 
     In the telecommunications industry, it would be desirable to package optical add-drop multiplexers in a modular form to allow for future expansion of service to customers. It would also be desirable to reduce the cost and complexity of the installation and integration of the multiplexers into telecommunications systems and allow for easy access to the multiplexers. 
     SUMMARY 
     The present invention relates to a telecommunications assembly including a chassis and a plurality of modules mounted within the chassis. The modules include one or more fiber optic connectors for receiving an input signal (or outputting an output signal). Within an interior of the module is located an optical multiplexer/demultiplexer. As a receiver, the multiplexer/demultiplexer is configured to demultiplex multiple optical carrier signals carried by the single input optical fiber into different wavelengths of laserlight as customer output signals. As a transmitter, the multiplexer/demultiplexer is configured to multiplex the customer signals, which are different wavelengths of laserlight, and combine them into a single optical fiber to be outputted at the one or more fiber optic connectors of the module. 
     Within the interior of the chassis, at each mounting location are positioned corresponding fiber optic adapters. Inserting the multiplexer module into the chassis at a mounting location positions the one or more connectors of the module for insertion into and mating with the adapters of the chassis. 
     The present invention further relates to a method of mounting a multiplexer module within a telecommunications chassis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the description, illustrate several aspects of the inventive features and together with the detailed description, serve to explain the principles of the disclosure. A brief description of the drawings is as follows: 
         FIG. 1  is a rear perspective view of a telecommunications assembly with a plurality of fiber optic splitter modules installed within a chassis, with one of the adapter assemblies exploded out of the telecommunications assembly; 
         FIG. 2  is a top view of the telecommunications assembly of  FIG. 1 ; 
         FIG. 3  is a front view of the telecommunications assembly of  FIG. 1 ; 
         FIG. 4  is a rear view of the telecommunications assembly of  FIG. 1 ; 
         FIG. 5  is a left side view of the telecommunications assembly of  FIG. 1 ; 
         FIG. 6  is a right side view of the telecommunications assembly of  FIG. 1 ; 
         FIG. 6A  illustrates a front perspective of the chassis of the telecommunications assembly of  FIG. 1 , shown with one fiber optic splitter module mounted therein; 
         FIG. 7  is a close-up view of the telecommunications assembly of  FIG. 1  showing the adapter assembly exploded out of the telecommunications assembly; 
         FIG. 8  is a front perspective view of one of the adapter assemblies of  FIG. 1 ; 
         FIG. 9  is a rear perspective view of the adapter assembly of  FIG. 8 ; 
         FIG. 10  is a right side view of the adapter assembly of  FIG. 8 ; 
         FIG. 11  is a left side view of the adapter assembly of  FIG. 8 ; 
         FIG. 12  is a front view of the adapter assembly of  FIG. 8 ; 
         FIG. 13  is a rear view of the adapter assembly of  FIG. 8 ; 
         FIG. 14  is a top view of the adapter assembly of  FIG. 8 ; 
         FIG. 15  is a bottom view of the adapter assembly of  FIG. 8 ; 
         FIG. 16  is a right side view of one of the fiber optic splitter modules of  FIG. 1 , shown with an adapter assembly mounted thereon; 
         FIG. 17  is a left side view of the fiber optic splitter module and adapter assembly of  FIG. 16 ; 
         FIG. 18  is a front view of the fiber optic splitter module and adapter assembly of  FIG. 16 ; 
         FIG. 19  is a rear view of the fiber optic splitter module and adapter assembly of  FIG. 16 ; 
         FIG. 20  is a front perspective view of the fiber optic splitter module of  FIG. 16 , shown in isolation without an adapter assembly mounted thereon; 
         FIG. 21  is a rear perspective view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 22  is an exploded view of the fiber optic splitter module of  FIG. 16 , shown with the adapter assembly exploded from the fiber optic splitter module; 
         FIG. 23  is a left side view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 24  is a right side view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 25  is a front view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 26  is a rear view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 27  is a top view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 28  is a bottom view of the fiber optic splitter module of  FIG. 20 ; 
         FIG. 29  is a right side view of the fiber optic splitter module of  FIG. 20 , shown without a cover exposing the interior features of the fiber optic splitter module including routing of a fiber optic cable within the fiber optic splitter module; 
         FIG. 30  is a cross-sectional view taken along section line  30 - 30  of  FIG. 29 ; 
         FIG. 31  illustrates a fiber optic splitter module partially inserted within the chassis of  FIG. 1 , the chassis including an adapter assembly mounted thereon, the fiber optic splitter module shown in a position prior to the connectors of the splitter module having contacted a shield located within the chassis; 
         FIG. 32  illustrates the fiber optic splitter module of  FIG. 31 , shown in a position within the chassis with the connectors of the fiber optic splitter module making initial contact with the shield located within the chassis; 
         FIG. 33  illustrates the fiber optic splitter module of  FIG. 31 , shown in a fully inserted position within the chassis; 
         FIG. 34  is a side cross-sectional view of the fiber optic splitter module of  FIG. 32  within the chassis, taken through the center of the fiber optic splitter module; 
         FIG. 35  is a side cross-sectional view of the fiber optic splitter module of  FIG. 33  within the chassis, taken through the center of the fiber optic splitter module; 
         FIG. 36  illustrates a front perspective view of a fiber optic wavelength-division multiplexing (WDM) module having features that are examples of inventive aspects in accordance with the present disclosure, the WDM module configured to be inserted within the chassis that is shown in  FIGS. 1-6 ; 
         FIG. 37  is a rear perspective view of the WDM module of  FIG. 36 ; 
         FIG. 38  is an exploded view of the WDM module of  FIG. 36 ; 
         FIG. 39  is a right side view of the WDM module of  FIG. 36 , shown without a cover exposing the interior features of the module including routing of fiber optic cables within the module; 
         FIG. 40  is a front perspective view of the main housing portion of the WDM module of  FIG. 36 , the main housing portion shown without the internal components mounted therein; 
         FIG. 41  is a rear perspective view of the main housing portion of  FIG. 40 ; 
         FIG. 42  is a right side view of the main housing portion of  FIG. 40 ; 
         FIG. 43  is a left side view of the main housing portion of  FIG. 40 ; 
         FIG. 44  is a front view of the main housing portion of  FIG. 40 ; 
         FIG. 45  is a cross-sectional view of the main housing portion of  FIG. 40  taken along line  45 - 45  of  FIG. 43 ; 
         FIG. 46  is a rear perspective view of the cover of the WDM module of  FIG. 36 ; 
         FIG. 47  is a right side view of the cover of  FIG. 46 ; and 
         FIG. 48  is a left side view of the cover of  FIG. 46 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary aspects of the present invention 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 similar parts. 
       FIGS. 1-7  illustrate a telecommunications assembly  10  that includes a telecommunications chassis  12  and a plurality of fiber optic splitter modules  14  adapted to be mounted within chassis  12 . Fiber optic splitter modules  14  are configured to be slidably inserted within chassis  12  and be optically coupled to adapter assemblies  16  mounted within chassis  12 . Adapter assemblies  16  mounted within chassis  12  form connection locations between connectors terminated to an incoming fiber optic cable and connectors of splitter modules  14  as will be discussed in further detail below. 
     Still referring to  FIGS. 1-7 , chassis  12  includes a top wall  18  and a bottom wall  20  extending between a pair of opposing transverse sidewalls,  22 ,  24 . Chassis  12  includes an opening  26  through a rear side  28  of chassis  12  and an opening  30  through a front side  32  of chassis  12 . Fiber optic splitter modules  14  are inserted into chassis  12  through front opening  30 . Adapter assemblies  16  are inserted through and mounted adjacent rear opening  26  of chassis  12 . Sidewalls  22 ,  24 , each include a cut-out  34  extending from front opening  30  toward rear side  28 . Splitter modules  14  mounted within chassis  12  are visible through cut-out  34 . Sidewalls  22 ,  24  of chassis  12  also define an inset portion  36  at rear side  28  of chassis  12  to facilitate access to adapter assemblies  16 . 
     In  FIG. 1 , chassis  12  is shown with eight fiber optic splitter modules  14  mounted thereon. It should be noted that in other embodiments, the chassis may be sized to hold a larger or a smaller number of splitter modules. As will be described further below, it should be noted that the chassis may hold modules other than splitter modules, such as modules housing fiber optic multiplexers. A fiber optic splitter is only one example of telecommunications equipment that might be supported by the module. 
     Still referring to  FIGS. 1-7 , chassis  12  includes a plurality of mounting locations  38  for slidably receiving splitter modules  14 . Each mounting location  38  defines a slot  40  adjacent top wall  18  and a slot  42  adjacent bottom wall  20  of chassis  12 . Slots  42  adjacent bottom wall  20  are visible in  FIG. 1 . Slots  40  adjacent top wall  18  are illustrated in  FIG. 6A . Slots  40 ,  42  extend from front  32  of chassis  12  to rear  28  of chassis  12 . Slots  40 ,  42  are configured to receive mounting flanges  44 ,  46  of splitter modules  14  as shown in  FIG. 6A  to align modules  14  with other components within chassis  12  (e.g., adapters of the adapter assemblies) to mate with pre-connectorized and/or pre-installed transmission cables. 
     Slots  40  defined underneath top wall  18  of chassis  12  are deeper than slots  42  defined at bottom wall  20  of chassis  12 . The depth of slots  40 ,  42  are configured to accommodate the different sized flanges  44 ,  46  that are defined at top and bottom walls of splitter modules  14 . In this manner, slots  40 ,  42  and mounting flanges  44 ,  46  of fiber optic splitter modules  14  provide a keying system to ensure that modules  14  are inserted into chassis  12  in the correct orientation. 
     Slots  40  underneath top wall  18  of chassis  12  are defined between a plurality of bulkheads  48  (please see  FIG. 6A ). Bulkheads  48  extend from front  32  of chassis  12  to rear  28  of chassis  12 . At front end  32  of chassis  12 , each bulkhead  48  defines a downwardly extending front lip  50  ( FIG. 35 ) which interlocks with a resiliently deformable latch  52  (e.g., cantilever arm) of splitter module  14  to hold splitter module  14  in place within chassis  12 , as will be discussed in further detail below. 
     Referring to  FIGS. 1 and 7 , at rear end  28  of chassis  12 , each bulkhead  48  defines a rear face  54  with a fastener hole  56  for receiving a fastener  58  (e.g., a thumbscrew) of an adapter assembly  16  for mounting adapter assembly  16  to chassis  12 . In the embodiment shown, fastener hole  56  is threaded to receive a screw-type fastener. It should be noted that in other embodiments, other types of fastening structures may be used to mount adapter assembly  16  to rear  28  of chassis  12 . 
     Adjacent rear end  28 , each bulkhead  48  also includes a horizontal slot  60  and a vertical slot  62  that complement the shape of adapter assembly  16  to slidably receive adapter assembly  16 . 
       FIGS. 8-15  illustrate adapter assembly  16  according to the invention. Adapter assemblies  16  form connection locations between the connectors terminated to an incoming fiber optic cable and the connectors of splitter modules  14  mounted within chassis  12 . 
     Referring to  FIGS. 8-15 , adapter assembly  16  includes two integrated adapters  64  formed as a part of a unitary housing  66 . In other embodiments, other number of adapters are also possible. Each adapter  64  of adapter assembly  16  includes a front end  68  and a rear end  70 . Front end  68  of each adapter  64  receives a connector of fiber optic splitter module  14  and rear end  70  receives a connector terminated to an incoming fiber optic cable. 
     Adapter assembly housing  66  includes a chassis-mounting slide  72  extending from a top  74  of housing  66 , which is received within chassis  12  through rear end  28 . Slide  72  defines a horizontal portion  76  and a vertical portion  78 . Horizontal portion  76  is configured to be slidably received within horizontal slot  60  of bulkhead  48  and vertical portion  78  is configured to be slidably received within vertical slot  62  of bulkhead  48 . 
     Chassis-mounting slide  72  includes a pair of flanges  80  for supporting a fastener  58  for securing adapter assembly  16  to chassis  12 . As discussed earlier, fastener  58  is positioned within an opening  56  defined by rear face  54  of bulkheads  48  located underneath top wall  18  of chassis  12 . Fastener  58  is preferably a captive fastener. In the embodiment of the adapter assembly shown in the figures, fastener  58  is a thumbscrew. In other embodiments, other types of fasteners may be used. 
     Fastener  58  is rotated to threadingly couple the adapter assembly  16  to the bulkheads  48 . Fastener  58  is also configured such that it is able to provide adapter assembly  16  with a predetermined amount of horizontal float relative to the chassis  12  once mounted thereon. As illustrated in  FIGS. 8-14 , the fastener  58  of the adapter assembly  16  includes a flange  81 . The fastener  58  is able to move horizontally within the flanges  80  relative to the adapter assembly housing  66 . As shown in  FIG. 35 , once mounted to the chassis  12 , the adapter assembly housing  66  is able to float or move horizontally with respect to the fastener  58  between flange  81  and the rear face of the bulkhead  48 . For example, in  FIG. 35 , adapter assembly  16  is shown to be able to move or float a distance of A toward the rear end of chassis  12 . In this manner, when a splitter module  14  is slidably pulled out of chassis  12  during disengagement, adapter assembly  16  is able to horizontally float a distance A towards splitter module  14  as the engaged connector  118  of splitter module  14  pulls on adapter  64  of adapter assembly  16 . In this manner, adapter assembly  16  is provided with a certain amount of horizontal float when being engaged to and disengaged from splitter module  14 . 
     Elements of each adapter  64  are positioned through a side opening into adapter recesses formed within the adapter assembly housing  66 . The elements for each adapter  64  include a ferrule alignment sleeve and a pair of inner housing halves. These elements are placed within recesses in manner similar to that shown in commonly-owned U.S. Pat. No. 5,317,663, issued May 20, 1993, entitled ONE-PIECE SC ADAPTER, the disclosure of which is incorporated herein by reference. A panel closes opening and secures the elements within each adapter  64 . Adapters  64  shown are for SC style connectors, although other types, styles and formats of adapters may be used within the scope of the present disclosure and connectors to mate with these alternative adapters. 
     A grip extension  218  ( FIGS. 1 and 7 ) may be used with connectors  118  coupled to rear  70  of adapters  64  of adapter assembly  16 . Grip extension  218  is designed to add length to the outer housing  150  of a connector  118  to facilitate access to individual connectors  118  in dense environments such as the telecommunications assembly  10 . Grip extension is preferably first mounted over a cable before the cable is terminated to a connector  118 . Once the connector  118  is terminated to the cable, grip extension  218  is slid over the boot portion  220  of the connector and mounted to the outer housing  150  of connector  118  as shown in  FIG. 7 . 
     In  FIGS. 16-19 , adapter assembly  16  is shown mounted to a fiber optic splitter module  14 , outside of chassis  12 . 
       FIGS. 20-30  illustrate one of the fiber optic splitter modules  14  according to the invention. Referring to  FIGS. 20-30 , the fiber optic splitter module  14  includes a splitter module housing  92 . Splitter module housing  92  includes a main housing portion  94  and a removable cover  96 . Main housing portion  94  includes a first transverse sidewall  98  extending between a top wall  100 , a bottom wall  102 , a rear wall  104 , and a front wall  106 . Removable cover  96  defines a second transverse wall  108  of splitter module housing  92  and closes off the open side of module main housing  94 . 
     Cover  96  is mounted to main housing portion  94  by fasteners (not shown) through fastener mounts  110  defined on main housing portion  94 . Cover  96  extends beyond first transverse sidewall  98  to form a top mounting flange  44  and a bottom mounting flange  46  of splitter module  14 . Referring to  FIGS. 23 ,  25 , and  26 , as discussed previously, bottom flange  46  of splitter module housing  92  and the corresponding slot  42  on chassis  12  are smaller in size than top flange  44  and the corresponding top slot  40  on chassis  12 . Bottom slot  42  is sized so that, while bottom flange  46  may be received within slot  42 , the larger top flange  44  will not fit. This ensures that modules  14  are positioned within front opening  30  in a particular desired orientation. Similar flanges are described in commonly-owned U.S. Pat. No. 5,363,465, issued Nov. 8, 1994, entitled FIBER OPTIC CONNECTOR MODULE, the disclosure of which is incorporated herein by reference. In this manner, fiber optic modules  14  are oriented correctly to be coupled to adapter assemblies  16  mounted adjacent rear  28  of chassis  12  at each mounting location  38 . 
     Rear wall  104  of main housing portion  94  includes a curved portion  112  configured to provide bend radius protection to cables within interior  114 . Rear wall  104  of main housing  92  also includes an inset portion  116 . A pair of fiber optic connectors  118  positioned at inset portion  116  protrude rearwardly from rear wall  104  for mating with fiber optic adapters  64  of adapter assemblies  16  mounted within chassis  12 . 
     As shown in  FIGS. 5 and 6 , front wall  106  of module main housing  94  is angled with regard to front opening  30  of chassis  12 , which may aid in the direction of cables exiting module  14  toward a desired location. In other embodiments, front walls  106  could be made generally parallel to front  32  of chassis  12  within the scope of the present disclosure. 
     Each module  14  includes two cable exits  120  extending from front wall  106  of module main housing  94 . As shown in  FIG. 22 , cable exits  120  are slidably mounted to main housing  94  of module  14  and captured by cover  96  of module  14  when cover  96  is mounted to main housing  94 . Cable exits  120  define a protruding rear lip  122  that is slidably inserted into slots  124  defined around front apertures  126  for accommodating cable exits  120 . Cover  96  also includes slits  128  that receive rear lips  122  of the cable exits  120  to capture cable exits  120 . Cable exits  120  permit telecommunications cables within module  14  to be directed outside of module  14 . Cable exits  120  are preferably sized thin enough to fit within the profile of the fiber optic splitter module  14 , as shown in  FIG. 25 , to preserve the density of the telecommunications assembly  10 . 
     Main housing  94  includes an integrally formed flexible latch  52  (i.e., cantilever arm) that is adapted to engage a portion of chassis  12  to hold module  14  within front opening  30  of chassis  12 . Flexible latch  52  also deflects to permit withdrawal of module  14  from chassis  12 . 
     Still referring to  FIGS. 20-30 , latch  52  of module  14  includes a finger grip tab  130 , a front latching tab  132  and a rear latching tab  134 . Front latching tab  132  and rear latching tab  134  define a recess  136  thereinbetween. Rear latching tab  134  includes a ramped face  138  that causes latch  52  to elastically deflect down when module  14  is being inserted into chassis  12 . Rear latching tab  134  also includes a square face  140  that opposes a square face  142  of front latching tab  132 . 
     Front lip  50  of bulkhead  48  at mounting location  38  of chassis  12  is captured in recess  136  between the two latching tabs  132 ,  134  to hold module  14  in place within chassis  12 . During insertion, as front lip  50  of bulkhead  48  clears ramped rear tab  134  and is captured in recess  136  between the two latching tabs  132 ,  134 , latch  52  flexes back upwardly. Recess  136  between the two tabs  132 ,  134  of latch  52  allows for a certain amount of horizontal float for splitter module  14  within chassis  12 , as will be discussed in further detail below. 
     The removal of module  14  from chassis  12  is performed by pressing latch  52  downwardly to clear the square face  140  of rear tab  134  from lip  50  and sliding module  14  away from chassis  12 . Module  14  includes a fixed grip tab  144  opposing and adjacent to flexible latch  52  to aid removal of module  14  from chassis  12 . Fixed grip tab  144  is formed as a part of front wall  106  of module  14 . Fixed grip tab  144  is preferably positioned on module  14  opposite latch  52  so that a user may apply opposing force on latch  52  and fixed grip tab  144  to securely grasp module  14  and remove it from chassis  12 . Fixed grip tab  144  is preferably positioned on module  14  close enough to latch  52  so that a user may be apply the force with two adjacent fingers of the hand. 
       FIG. 22  shows an exploded view of fiber optic splitter module  14  illustrating the internal components of module  14 . Fiber optic splitter module  14  is shown in  FIG. 22  with adapter assembly  16  exploded from module  14 . 
     Within interior  114  of main housing  94 , splitter module  14  includes a first radius limiter  146  adjacent curved portion  122  of rear wall  104  of main housing  94 . Splitter module  14  includes a second radius limiter  148  adjacent front wall  106  of housing  94  near cable exits  120 . Connectors  118  of splitter module  14  are slidably inserted into opposing slots  154  formed in apertures  156  at the rear wall  104 . Connectors  118  project out from rear wall  104  at inset portion  116  of rear wall  104 . Outer housings  150  of connectors  118  include transverse flanges  152  that are received within the opposing slots  154  formed in apertures  156  that accommodate the connectors  118 . Once slidably inserted, connectors  118  are captured within housing  92  by cover  96 . 
     Adjacent bottom wall  102  of main housing  94  within interior  114  is an optical component  158  such as a fiber optic splitter or a fan-out. Optical component  158  is held against the interior of bottom wall  102  by a clamp  160  (i.e., bracket). Clamp  160  is mounted to a clamp mount  162  defined on splitter module main housing  94  with fasteners (not shown). In the embodiment of the housing  94  shown in the figures, clamp mount  162  includes two pairs of mounting holes  164 ,  166 . Either the upper set of holes  164  or the lower set of holes  166  are utilized depending upon the size of the clamp that will be used to hold optical component  158  against bottom wall  102 . It should be noted that different optical components may have different thicknesses and may require the use of different sized clamps for holding the optical components in place. In certain embodiments, two optical components that are stacked on top of another may be used, in which case, a smaller clamp would be used to hold the two optical components in place. 
     Optical component  158  is offset from the interior side of first transverse sidewall  98  by a set of cable management structures  168 . In the embodiment of the module  14  illustrated, the set of cable management structures  168  are elongate structures  170  defining cable management slits  172  therein between. When optical component  158  is held in place, cables can be routed through slits  172  between optical component  158  and the interior of first transverse wall  98  (please see  FIGS. 29 and 30 ). 
     Splitter module main housing  94  also includes integrally formed crimp holders  174  (e.g., slots) adjacent front wall  106  of housing  94  underneath second radius limiter  148 . Crimp elements  176  crimped to the ends of cables that are split by optical component  158  are slidably received into crimp holders  174  as shown in  FIGS. 22  and  29 . Crimp elements  176  define square flanges  175  between which is defined a recessed portion  177 . The crimp holders  174  include complementary structure to the crimp elements such that once the crimp elements  176  are slidably inserted into the crimp holders  174 , the crimp elements  176  are prevented from moving in a longitudinal direction due to the flanges  175 . Once slidably inserted, crimp elements  176  are held in place by cover  96  that is mounted to splitter module main housing  94 . In the embodiment shown, there are nine crimp holding slots  174 , each one being able to accommodate up to four crimp elements  176 . Other numbers are possible. Other complementary shapes between the crimp elements and the crimp holding slots are also possible to provide a slidable fit and to prevent axial movement of the crimp elements once inserted therein the crimp holders. 
       FIG. 29  shows fiber optic splitter module  14  without a cover  96  exposing the interior features of fiber optic splitter module  14  including routing of a fiber optic cable within fiber optic splitter module  14 .  FIG. 30  illustrates a cross-sectional view taken along section line  30 - 30  of  FIG. 29 . 
     As shown in  FIG. 29 , a first cable  178  extends from connector  118  toward optical component  158 , mounted within module housing  92 . Optical component  158 , as previously discussed, may be a splitter or a fan-out or another type of optical component. In the embodiment shown, optical component  158  is a fiber optic splitter that splits the signal of a single strand to a plurality of secondary signals. In another embodiment, first cable  178  may be a multi-strand fiber cable with a plurality of strands of optical fiber and optical component may be a fanout to separate the individual strands into each of a plurality of second cables. 
     First cable  178 , as it extends toward optical component  158 , is inserted through slits  172  (see  FIGS. 22 ,  29 , and  30 ) located between optical component  158  and the inner side of first transverse sidewall  98  of module housing  94  and looped around first radius limiter  146  and then around second radius limiter  148  before being received by optical component  158 . Second cables  180  extend from optical component  158  and are looped again all the way around first radius limiter  146  before heading toward crimp holders  174 . From crimp holders  174 , cables (not shown) crimped to the other ends of the crimps  176  exit the module through module exits  120 . 
     An outside cable (not shown) may extend to rear end  70  of an adapter  64  of adapter assembly  16  and be terminated by a connector (not shown in  FIG. 29 ) that is optically connected to connector  118  of module  14  through adapter  64  once module  14  is inserted within chassis  12 . It should be noted that the routing of the fiber optic cables within module  14  as shown in  FIGS. 29 and 30  is only one example and other ways of routing the cables within the module are possible. 
     The embodiment of the fiber optic splitter module  14  shown in the figures is configured such that it can accommodate reduced bend radius fiber. A reduced bend-radius fiber may have a bend radius of about 15 mm whereas a non-reduced bend-radius fiber may have a bend radius of about 30 mm. 
     Similar fiber optic splitter modules are described in commonly-owned U.S. patent application Ser. Nos. 10/980,978 (filed Nov. 3, 2004, entitled FIBER OPTIC MODULE AND SYSTEM INCLUDING REAR CONNECTORS); 11/138,063 (filed May 25, 2005, entitled FIBER OPTIC SPLITTER MODULE); 11/138,889 (filed May 25, 2005, entitled FIBER OPTIC ADAPTER MODULE); and 11/215,837 (filed Aug. 29, 2005, entitled FIBER OPTIC SPLITTER MODULE WITH CONNECTOR ACCESS), the disclosures of which are incorporated herein by reference. 
     The insertion of a splitter module  14  into chassis  12  is illustrated in  FIGS. 31-35 . Referring to  FIGS. 31-35 , insertion of fiber optic module  12  into front opening  30  of chassis  12  begins the mating of module  14  to chassis  12  and to adapters  64  of adapter assembly  16 . Top flanges engage  44  top slots  40  and bottom flanges  46  engages bottom slots  42  of chassis  12  as module  14  is inserted. 
     Still referring to  FIGS. 31-35 , chassis  12  includes a flexible shield  182  in each mounting location  38 . Shield  182  is adapted to prevent protection against accidental exposure to light. Shield  182  is positioned in front end  68  of each adapter  64  of adapter assembly  16 . Before a splitter module  14  is placed in an associated mounting location  38 , if a connectorized cable that is connected to an adapter  64  of adapter assembly  16  is illuminated and transmitting light signals, shield  182  will prevent accidental exposure to these signals which might damage eyes or other sensitive organs, or nearby communications equipment. The insertion of splitter module  14  pushes shield  182  out of the way as illustrated in  FIGS. 31-33 . 
     Shield  182  is deflected by module  14  as module  14  is inserted through front opening  30  so that connectors  118  of module  14  can mate with adapters  64  of adapter assemblies  16 . Shield  182  is preferably made of a resilient deformable material that will return to the position when module  14  is withdrawn from mounting location  38 . 
     For example, in  FIG. 31 , a fiber optic splitter module  14  is shown partially inserted within chassis  12  prior to connectors  118  of splitter module  14  having contacted shield  182  of chassis  12 . In  FIG. 32 , fiber optic splitter module  14  is shown in a position within chassis  12  with connectors  118  of fiber optic splitter module  14  making initial contact with shield  182  of chassis  12  to move shield  182  out of the way (a side cross-sectional view is shown in  FIG. 34 ). In  FIG. 33 , fiber optic splitter module  14  is shown in a fully inserted position within chassis  12 , having moved shield  182  out of the way (a side cross-sectional view is shown in  FIG. 35 ). 
     Shield  182  is configured such that shield  182  does not engage the ferrule  184  of connector  118  of splitter module  14  when connector  118  contacts shield  182  to move it out of the way. Instead, outer connector housing  150  pushes shield  182  out of the way. 
     Shield  182  may be connected to chassis  12  by fasteners, or, alternatively, shield  182  may be formed integrally with chassis  12  or mounted by spot-welding or other fastening techniques. 
     As shield  182  is fully deflected, further insertion of module  14  brings connectors  118  into contact with adapters  64  and connectors  118  are received within front ends  68  of adapters  64 . Latch  52  is deflected inwardly as module  14  is inserted and then flexes back so that front lip  50  of bulkhead  48  is captured in recess  136 . Module  14  is now in position to process and transmit signals from cable through first cable  178 , optical component  158  and second cable  180  within module interior  114 . 
     Referring to  FIG. 35 , as noted above, recess  136  between the two tabs  132 ,  134  of latch  52  provides a certain amount of horizontal float for the splitter module  14  within chassis  12 . Front lip  50  of bulkhead  48  is allowed to move a distance of D as indicated in  FIG. 35  before it makes contact with square face  140  of rear tab  134 . Splitter module  14  is configured such that, when splitter module  14  is pulled away from front  32  of chassis  12 , distance D front lip  50  of bulkhead  48  travels before contacting square face  140  of rear tab  134  is less than the horizontal float (i.e., distance A) provided for adapter assembly  16 , as discussed before. 
     In this manner, splitter module  14  provides a form of protection from accidentally disengaging connectors  118  of the module from adapter assemblies  16  at rear  28  of chassis  12 . The size of recess  136  of module  14  is configured such that the horizontal float of splitter module  14  is interrupted before the adapter assembly  16  can be pulled far enough toward the front of chassis  12  to stop its horizontal movement and accidentally disengage connectors  118  of module  14  from adapters  64 . 
       FIGS. 36-39  illustrate a fiber optic wavelength division multiplexing (WDM) module  214  having features that are examples of inventive aspects in accordance with the present disclosure. The WDM module  214  is configured similarly to the splitter module  14  of  FIGS. 20-30  in certain aspects. For example, the WDM module  214  is configured to be inserted within the chassis  12  in a similar manner as module  14 . However, the WDM module  214  houses a fiber optic multiplexer/demultiplexer  358  and the features of the module  214  are configured for supporting the multiplexer/demultiplexer  358  and integrating into a telecommunications system. As will be discussed in detail, the WDM module  214  includes internal features for housing the multiplexer/demultiplexer  358  and routing and managing cables to and from the multiplexer/demultiplexer  358  and external features for integrating the multiplexer/demultiplexer  358  into a telecommunications assembly including a chassis  12 , such as the telecommunications assembly  10  of  FIGS. 1-7 . 
     Referring to  FIG. 38 , the WDM module  214  is shown in an exploded orientation. WDM module  214  includes a module housing  292  that includes a main housing portion  294  and a removable cover  296 . The main housing portion  294  is illustrated separately in  FIGS. 40-45  and the cover  296  is illustrated separately in  FIGS. 46-48 . The module housing  292  is configured to house a multiplexer/demultiplexer chip  358  therewithin for multiplexing/demultiplexing signals that are input and output through connectors  318  of the module  214 . The module housing  292  includes a cable exit  320  for relaying fiber signals to customers. 
     The WDM module  214  includes a number of cable management/routing features as will be described in further detail below. One of the cable management features includes the fiber retainer  360  that is removably mounted to the main housing portion  294  of the module housing  292 , as shown in  FIG. 38 . As also shown in  FIG. 38 , a label  361  including indicia relating to the module  214  may be mounted to the cover portion  296  of the housing  292 . 
     Still referring to  FIG. 38 , the main housing portion  294  defines a first sidewall  298  extending between a top wall  300 , a bottom wall  302 , a rear wall  304 , and a front wall  306 . Removable cover  296  defines a second sidewall  308  of the module housing  292  and closes off the open side of module main housing portion  294 . 
     Cover  296  is mounted to main housing portion  294  by fasteners through fastener holes  309  in the cover  296  and fastener mounts  310  defined on main housing portion  294 . Cover  296  extends beyond the first sidewall  298  to form a top mounting flange  244  and a bottom mounting flange  246  of the WDM module  214 , similar to the splitter module  14  (see  FIGS. 36 and 37 ). As discussed previously for chassis  12 , the bottom flange  246  and the corresponding slot  42  on chassis  12  are smaller in size than top flange  244  and the corresponding top slot  40  on chassis  12 . Bottom slot  42  is sized so that, while bottom flange  246  may be received within slot  42 , the larger top flange  244  will not fit. This ensures that the WDM modules  214  are positioned within front opening  30  of the chassis  12  in a particular desired orientation to be correctly coupled to adapter assemblies  16  mounted adjacent rear  28  of chassis  12  at each mounting location  38 . 
     Rear wall  304  of main housing portion  294  includes a curved portion  312  configured to provide bend radius protection to cables within interior of the module  214 . Similar to module  14 , the rear wall  304  of main housing  294  includes an inset portion  316  and a pair of fiber optic connectors  318  positioned at the inset portion  316 . The connectors  318  protrude rearwardly from rear wall  304  for mating with fiber optic adapters  64  of adapter assemblies  16  mounted within chassis  12 . 
     As shown in  FIGS. 40-43 , the front wall  306  of the module main housing  294  is angled with regard to front opening  30  of chassis  12 , which may aid in the direction of cables exiting the WDM module  214  toward a desired location. In other embodiments, front walls could be made generally parallel to front  32  of chassis  12  within the scope of the present disclosure. 
     As noted above, the embodiment of the WDM module  214  illustrated includes one cable exit  320  extending from front wall  306  of module main housing  294 . The cable exit  320  is slidably mounted to main housing  294  of the WDM module  214  and is captured by the cover  296  when cover  296  is mounted to main housing  294 . The cable exit  320  defines a protruding rear lip  322  that is slidably inserted into a slot  324  defined around a front aperture  326  for accommodating the cable exit  320 . Cover  296  also includes a slit  328  that receives the rear lip  322  of the cable exit  320  to capture the cable exit  320 . The cable exit  320  permits telecommunications cables within module  214  that have been multiplexed/demultiplexed to be directed outside of module  214 . The cable exit  320  is preferably sized thin enough to fit within the profile of the WDM module  214 , similar to splitter module  14 , as shown in  FIG. 25 , to preserve the density of the telecommunications assembly. 
     Referring to  FIGS. 40-45 , the main housing  294  includes an integrally formed flexible latch  252  (i.e., cantilever arm) that is adapted to engage a portion of chassis  12  to hold module within front opening  30  of chassis  12 . Flexible latch  252  also deflects to permit withdrawal of module from chassis  12 . The flexible latch  252  of the module  214  is constructed similarly to that of module  14  and operates in a similar manner for insertion and removal of the module from chassis  12 . As in module  14 , the latch  252  of module  214  includes a finger grip tab  330 , a front latching tab  332  and a rear latching tab  334  that cooperate with the bulkhead  48  at the mounting location  38  of the chassis  12 . The WDM module  214  also includes a fixed grip tab  344 , similar to module  14 , opposing and adjacent to flexible latch  252  to aid removal of module  214  from chassis  12 . Fixed grip tab  344  is preferably positioned on module  214  opposite latch  252  so that a user may apply opposing force on latch  252  and fixed grip tab  344  to securely grasp module  214  and remove it from chassis  12  with two adjacent fingers of the hand. The insertion of the WDM module  214  into chassis  12  is similar to that of module  14  and is described above with respect to  FIGS. 31-35 . 
     Still referring to  FIGS. 40-45 , within interior of main housing  294 , module  214  includes a first radius limiter  346  adjacent curved portion  322  of rear wall  304  of main housing  294 . The WDM module  214  includes a second radius limiter  348  adjacent front wall  306  of housing near the cable exit  320 . A third radius limiter  349  is located adjacent the front wall  306  below the second radius limiter  348 . As will be discussed in further detail below, the radius limiters  346 ,  348 ,  349  provide bend-protection to fiber cables within the module  214  while providing cable management/routing functionality. 
     Adjacent bottom wall  302  of main housing  294  within interior are located a first guide  364  and a second guide  366  for placement of the multiplexer chip  358  within the module  214 . A third guide  368  is located adjacent the first radius limiter  346 . The first radius limiter  346  defines a curved wall  415 . The curved wall  415  includes a first end  417  and a second end  419 . The first and second ends  417 ,  419  of the curved wall  415  also act as guides in positioning the multiplexer chip  358  within the main housing  294 . The first, second, and third guides  364 ,  366 ,  368  and the ends  417 ,  419  of the curved wall  415  of the first radius limiter  346  form a frame structure around the chip  358  for correctly positioning the multiplexer chip  358  within the interior of the main housing portion  294 . As shown in  FIGS. 38 and 39 , once the multiplexer chip  358  is placed within the guides, the chip  358  is held within the module  214  against the first sidewall  298  by the removable cover  296 . 
     The first sidewall  298  of the main housing  294  includes a first notch  370  for accommodating fiber cables that may extend underneath the multiplexer chip  358 . Once the chip  358  is placed within the main housing  294 , the notch  370  creates a space between the chip  358  and the first sidewall  298  and accommodates any cables routed between the chip  358  and the first sidewall  298 . 
     Still referring to  FIGS. 40-45 , the module main housing  294  also includes integrally formed crimp holders  374  (e.g., slots) adjacent front wall  306  of housing  294  in between the second and third radius limiters  348 ,  349 . Crimp elements  376  (see  FIGS. 38-39 ) crimped to the ends of cables that are multiplexed/demultiplexed by the chip  358  are slidably received into crimp holders  374 . Crimp elements  376  define square flanges  375  between which is defined a recessed portion  377 . The crimp holders  374  include complementary structure to the crimp elements  376  such that once the crimp elements  376  are slidably inserted into the crimp holders  374 , the crimp elements  376  are prevented from moving in a longitudinal direction due to the flanges  375 . Once slidably inserted, crimp elements  376  are held in place by the cover  296  that is mounted to module main housing  294 . In the embodiment shown, there are four crimp holding slots  374 , each one being able to accommodate up to four crimp elements  376 . Other numbers are possible. Other complementary shapes between the crimp elements and the crimp holding slots are also possible to provide a slidable fit and to prevent axial movement of the crimp elements once inserted into the crimp holders. 
     Now referring back to  FIGS. 36-39 , as in module  14 , connectors  318  of WDM module  214  are slidably inserted into opposing slots  354  formed in apertures  356  at the rear wall  304 . Connectors  318  project out from rear wall  304  at inset portion  316  of rear wall  304 . Connectors  318  of WDM module  214  are similar in construction to connectors  118  of the splitter module  14 . Connectors  318  of the WDM module  214  may function both as input connectors and output connectors since the WDM module  214  is configured to both demultiplex signals coming in and multiplex signals going out of the connectors  318 . The main housing  294  includes a reinforcement structure  311  extending from the sidewall  298  of the main housing  294 . The reinforcement structure  311  aligns and fits into a recess  491  defined on the sidewall  308  of the cover  296  (see  FIGS. 46 and 48 ) when the main housing  294  and cover  296  are assembled together. 
       FIGS. 46-48  illustrate the cover  296  of the WDM module  214 . The cover  296  is configured to be fastened to the module main housing portion  294 . As discussed previously, once mounted, the cover  296  defines different sized flanges  244 ,  246  for slidably inserting the module  214  within the chassis  12  and for correctly orienting the module  214  with respect to the chassis  12 . 
     The cover  296  defines a tab  373  adjacent the front end  371  thereof. The tab  373  is slidably inserted within a recess  431  defined at the front wall  306  of the main housing portion  294  (see  FIGS. 38 and 41 ) to correctly orient the cover  296  with respect to the main housing portion  294 . As shown in  FIG. 46 , the cover  296  also includes protruding portions  379  defined around the periphery and slots  381  defined between the protruding portions  379  that intermate with corresponding structures located around the periphery of the main housing  294  for correctly placing the cover  296  onto the main housing  294 . 
     As shown in  FIG. 46 , the cover  296  defines a second notch  372  on the second sidewall  308 . The second notch  372  is configured to accommodate the multiplexer chip  358  once the cover  296  is mounted on the main housing portion  294 . The cover  296  also defines slots  383  on the second sidewall  308  for receiving the structures of the main housing portion  294  that define the crimp holders  374  thereinbetween. The slots  383  are located in a notched area  385 . This third notch  385  accommodates the area of the main housing portion  294  with the crimp holders  374 . 
     The WDM module  214  is shown in  FIG. 39  with the cover  296  and the fiber retainer  360  removed from the main housing portion  294  to illustrate the internal components and to illustrate the cable routing. 
     One sample cable routing arrangement is shown in  FIG. 39 . Others are possible. As shown in  FIG. 39 , a first cable  378  extends from one of the connectors  318  toward and around the second radius limiter  348 . From the second radius limiter  348 , the first cable  378  extends downwardly toward the third radius limiter  349  and around the first guide  364  toward the rear of the module  214 . As the cable  378  extends from the first guide  364 , the cable  378  is positioned in a space  400  defined between the bottom wall  302  and the multiplexer chip  358 . After going around the second guide  366  and upwardly, the first cable  378  goes around the first radius limiter  346  and toward the front of the module  214 . The first cable  378  is, then, led around the second radius limiter  348  and the third radius limiter  349 . From the third radius limiter  349 , the first cable  378  enters the multiplexer chip  358 . The fiber optic signals that are input into the multiplexer  358  are demultiplexed and split into the different wavelengths that are carried by separate second cables  380  for service to different customers. 
     Once demultiplexed, second cables  380  extend from the chip  358  and are looped around the first radius limiter  346  and then extend underneath the chip  358  before they are looped again around the first radius limiter  346 . The first notch  370 , as discussed previously, accommodates the cables  380  going underneath the chip  358  between the sidewall  298  of the main housing  294  and the chip  358 . After the second cables  380  have been looped around the first radius limiter  346  again, they extend toward crimp holders  374 . From crimp holders  374 , cables crimped to the other ends of the crimps exit the module through exit as customer output pigtails  401 . 
     As noted above, the routing of the fiber optic cables within module  214  as shown in  FIG. 39  is only one example and other ways of routing the cables within the module are possible. 
     As shown in  FIG. 38 , a fiber retainer  360  may be placed on the main housing portion  294  to keep cables  380  wrapped around the first radius limiter  346 . The fiber retainer  360  is planar and includes a semicircular shape to match the contour of the curved portion  312  of the rear wall  304  of the main housing  294 . The fiber retainer  360  includes three tabs  403  positioned around the periphery. The three tabs  403  are placed within slots  405  formed around the curved portion  312  of the rear wall  304 . The fiber retainer  360  includes a semicircular opening  407  which accommodates a portion of the first radius limiter  346  that protrudes through the opening  407 . When the fiber retainer  360  is placed on the main housing portion  294 , it lies flush with the main housing portion  294  and is held thereagainst by the cover  296 . 
     It will be noted that the multiplexing chip  358  provides a two-way signal path for the signal going through it. Input signals input through the connectors  318  are demultiplexed and are split into different wavelengths and signals coming from the customers are multiplexed and combined into a single signal to be carried on a single fiber that is output also through the connectors  318 . For inputting and outputting signals, an outside cable (not shown) terminated by a connector is optically connected to a connector  318  of the module  214  through an adapter  64  of the adapter assembly  16 . This connection is established by the slidable insertion of the WDM module  214  into the chassis  12 . 
     According to one embodiment, the WDM module  214  may house a 1×4 dense wavelength division multiplexing chip. According to another embodiment, the WDM module may house a 1×8 dense wavelength division multiplexing chip. According to another embodiment, the WDM module may house a 1×16 dense wavelength division multiplexing chip. In another embodiment, the module may house a coarse wavelength division multiplexing chip. Other types of multiplexer chips are also contemplated. 
     According to one embodiment, an overlay filter chip may be used within the module  214 . Such a chip may be positioned in the space located between the bottom wall  302  of the main housing  294  of the module  214  and the multiplexer chip  358 . 
     The above specification, examples and data provide a complete description of the manufacture and use of the disclosure. Since many embodiments of the disclosure can be made without departing from the spirit and scope of the inventive aspects, the inventive aspects resides in the claims hereinafter appended.