Abstract:
A fiber distribution system having a rack mounted chassis and a fiber distribution rack to mount in the chassis. The system includes one or more splitter modules which are designed to be mounted in the fiber distribution rack. The splitter modules have a compact design and contain a plurality of fiber splitters. The system also includes a plurality of spools, which are located on opposite sides on the rack mounted chassis, and used to support the routing of fibers. The spools are configured to equally share the fiber load coupled to a fiber distribution rack between a pair of spools. The fiber distribution system also contains a cable guide tray for supporting the fiber cables and the system includes a plurality of radius limiters to minimize cable bends.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention relates to a high density central office fiber distribution system having a splitter module, a rack mountable panel, and double spools for reducing complexity, weight, and cost of a fiber distribution system. 
         [0003]    2. Background 
         [0004]    Central office fiber distribution systems call for high density fiber management and a substantial amount of splitting of fiber cable signals. Because of the amount of signal splitting required, the space needed to house the system increases with the density of fiber cable splitters. Likewise, when fiber cable routing is at high densities it makes the routing of the fiber cables difficult and it becomes a very difficult task to properly manage the fiber cables without causing sharp bends. The pressure caused by sharp bends usually results in signal strength loss. 
         [0005]    Known designs for central office fiber distribution systems use a swing-out panel design for fiber cable connections. These designs typically utilize the rear of the system for fiber cable entry. Because of the engineering of these designs, they require a large number of parts, are difficult to manage, and are very heavy. Not just anyone can work on the known designs for fiber cable distribution systems. Specialized tools and specially trained staff are typically needed to properly install and maintain them. 
         [0006]    In order to achieve some amount of organization, a fiber cable distribution system needs certain features which improve its utility. One such feature is a series of spools spaced amongst the panels. Spools are used to wrap, hang, and/or guide fiber cables before connection to the panel. Using the spool helps to eliminate slack and/or unwanted tension on the fiber cable. Known designs use a spool on only one side of a distribution panel. Thus, every fiber cable going to a nearby panel, no matter how close or how far away the connection is, uses the closest spool. This creates a higher fiber cable density at each spool and reduces fiber cable management quality. The higher the density of fiber cable, the greater the chances of damage occurring to a fiber cable. 
         [0007]    Because of the swing-out panel/module design of known systems, making fiber changes, while not impossible, is not easy. First, the panel must be opened and then the individual module that the fiber is connected to must be found and accessed. But this is all done with a maze of fibers interfering with straight-forward access. There is also a complex and burdensome rear cable entry method. Further, there is a chance that all the mechanical movement of the panel and module will introduce bends in the fibers and thereby degrade the transmitted signal quality. 
       SUMMARY 
       [0008]    According to an embodiment of the invention, there is provided a fiber distribution system (FDS) including a rack mounted chassis. The FDS has a fiber distribution rack that can be mounted to the chassis. The fiber distribution rack is configured to accept a plurality of splitter modules which are preloaded with multiple splitters of different configurations/types. The FDS further includes pairs of spools which are located on opposing sides of the rack mounted chassis. There is at least one such pair. By using pairs of spools, the fiber cable routing management can be improved which in turn helps prevent damage to fiber cables. 
         [0009]    In another embodiment of the invention, the splitter module is an integral part of the FDS and comprises a self-contained sealed enclosure including a plurality of splitters. The input side of the splitter modules have a face flange and a plurality of Splice Closure (SC) adapters. In order to affix the splitter modules to the fiber distribution rack, a pair of fasteners is included on the face flange of each splitter module. The splitter module also includes a smaller flange along another of its faces. This smaller flange is inserted into a pair of guides evenly spaced in the fiber distribution rack and allows for easy and controlled installation and removal of the splitter modules. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which: 
           [0011]      FIG. 1  is an example of a known fiber distribution system; 
           [0012]      FIG. 2  is a close-up view of a termination module in the fiber distribution system of  FIG. 1 ; 
           [0013]      FIG. 3  is a perspective view of a splitter module; 
           [0014]      FIG. 4  is a perspective view of a fiber distribution rack; 
           [0015]      FIG. 5A  depicts the splitter module of  FIG. 3  being lined-up for installation into the fiber distribution rack of  FIG. 4 ; 
           [0016]      FIG. 5B  depicts a stack of fiber distribution racks, with one rack housing two splitter modules; 
           [0017]      FIG. 5C  is a rear perspective of  FIG. 5B ; 
           [0018]      FIG. 5D  depicts a stack of fiber distribution racks, each with a full installation of splitter modules, as well as a front cable guide with radius ends; 
           [0019]      FIG. 6A  depicts a fiber distribution rack with full installation of splitter modules and showing fiber cable routing and connections; 
           [0020]      FIG. 6B  depicts a pair of fiber distribution racks, each with a full installation of splitter modules, but only one of the fiber distribution racks showing cable routing and connections.  FIG. 6B  also shows a front cable guide which is different from the one shown in  FIGS. 5D and 6A . 
           [0021]      FIG. 7  depicts an entire fiber distribution chassis, with a plurality of fiber distribution racks each housing a plurality of splitter modules; and 
           [0022]      FIG. 8  is a rear perspective of the fiber distribution chassis of  FIG. 7  showing the cable entrance and a rear cable guide.  FIG. 8  also shows a rear perspective of the splitter modules fully installed in the fiber distribution racks. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    While the invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those skilled in the art with access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention would be of significant utility. 
         [0024]    The present invention is directed to a central office fiber distribution system, such as a rack mountable plurality of splitter modules. A rack mountable chassis is combined with a plurality of cable guides and a plurality of spool pairs, oppositely positioned to efficiently and carefully route fiber cable into and out of the distribution rack. The embodiment of the invention illustrated and described hereinafter is constructed to improve high-fiber density management problems, to reduce the distribution system footprint, to reduce overall weight, and to be more cost effective. 
         [0025]    Referring now to the drawings,  FIG. 1  illustrates a known fiber distribution system  100 . The main components of fiber distribution system  100  are a rear located fiber storage rack  110 , a stack of termination modules  150 , which contain hinged panels  120  where the fiber connections are made, and a series of spools  130  along one edge of the termination module  150  stack.  FIG. 2  is a close-up view of the termination module  150  in the fiber distribution system  100  of  FIG. 1 . The termination module  150  is housed in a protective enclosure  200  and is accessible via the hinged panel  120  which pivots on a hinge  230 . Internal to termination module  150  is a set of fiber cable guides  220  and a set of fiber terminations  210 . 
         [0026]    The issues with the known designs for fiber distribution systems  100  in  FIG. 1  is that the fiber cables are all concentrated into a couple of locations: the rear fiber storage rack  110  and the spools  130  along one side. This creates a high density of fiber cables and creates fiber cable management problems which can increase the chances of fiber cable damage. In addition to increased chance of cable damage, the design of  FIG. 1  also has an increased complexity to new installation and/or modification of existing connections. Fiber cables must be routed in and out of the rear of the termination module  150 . Also, in order to connect or disconnect any fiber cable, an installer must unscrew and hinge-out the panel  120  of the termination modules  150  involved. This set-up is not conducive to quick and/or easy modification to the fiber cable connections which comprise the fiber distribution system  100 . With these issues in mind, embodiments of the present invention are designed to eliminate high fiber cable density, installation complexity, and overall size, weight, and cost. 
         [0027]    Turning now to  FIG. 3 , one of the components of the new design is the splitter module  300 . The splitter module  300  includes a sealed enclosure  310  which has two flanges: a face flange  330 , and a guide flange  320  along one of its sides. The splitter module  300  also includes a pair of fasteners  340 . In at least one embodiment, the fasteners  340  comprises a pair of nylatches. Nylatches are usually made of plastic and include a pin and a grommet which fit together through an opening in the face flange  330 . The grommet can then be inserted into an opening on a fixed panel. Once installed a simple push/pull is all that is required to engage/disengage the nylatch. This allows for simple fastening/unfastening of the splitter module  300  to/from a fixed panel. 
         [0028]    The splitter module  300  also includes a set of Splice Closure (SC) adapters  250 . In the example of  FIG. 3 , six adaptors  250  are shown. It would be apparent to one skilled in the art that any number of adaptors  250  could be used. The splitter module  300  houses a plurality of splitters. The splitters can be of many different types and/or configurations. In at least one embodiment, the different types/configurations could be 2:1, 3:1, 4:1 splitters and could have multiple attenuation characteristics such as a 2:1 with 95% attenuation for one signal and 5% attenuation for the other. These examples are in no way limiting and one skilled in the art would recognize that numerous combinations of types and configurations are envisioned in the embodiments of the present invention. 
         [0029]      FIG. 4  shows a fiber distribution rack  400 . Key features of the fiber distribution rack  400  are module guides  410 , module guide cutouts  440 , and fastener receptors  420 . In the illustrated embodiment of  FIG. 4 , the form factor of fiber distribution rack  400  is that of a standard 19 inch mountable rack, although other form factors are also contemplated. Also in this illustrated embodiment, the height of the fiber distribution rack  400  is 2U (where 1U=1.75 in). In order to affix fiber distribution rack  400  to a rack mounted chassis (not shown), a set of mounting holes  430  are fashioned along each side of fiber distribution rack  400 . In one embodiment, mounting holes  430  are spaced at about 0.625 inches center-to-center. 
         [0030]      FIGS. 5A-D  depict how the two components work together in the new design. In  FIG. 5A , the guide flange  320  of the splitter module  300  is at the cusp of the module guide cutouts  440 , which are directly in-line with the module guides  410 . In order to fully install the splitter module  300  into the fiber distribution rack  400 , the installer must move the splitter module  300  in the direction of motion illustrated in  FIG. 5A . While installing the splitter module  300 , the guide flange  320  follows the upper and lower guides  410  until the face flange  330  of the splitter module  300  lies flush with the fiber distribution rack  400 . Once the face flange  330  and the fiber distribution rack  400  engage, the fasteners  340  and the fastener receptors  420  should line up and the splitter module  300  can be affixed to the fiber distribution rack  400  by inserting the fasteners  340  into the fastener receptors  420 . It is, however, never a requirement that the splitter unit  300  be fully affixed to the fiber distribution rack  400 ; the splitter module is fully functional at any position within the module guides  410 . 
         [0031]      FIG. 5B  shows a stack of fiber distribution racks  400  housed in a rack mountable chassis, with one rack housing, for example, two splitter modules  300 . In this view, the two splitter modules  300  are fully installed (fasteners  340  engaged) and located side by side within the fiber distribution rack  400 . The use of the module guides  410  ensures that the splitter modules  300  are kept straight and correctly spaced within the fiber distribution rack  400 . 
         [0032]      FIG. 5C  is a rear perspective of  FIG. 5B . This view provides a view of the guide flange  320  engaged with the upper module guide  410 . 
         [0033]      FIG. 5D  depicts a stack of fiber distribution racks  400 , each comprising a full installation of splitter modules  300 . In addition to the splitter modules  300 , the fiber distribution rack  400  has a front cable guide  520  which supports the fiber cable that is destined to be connected to one of the SC adapters  350  of one of the splitter modules  300 .  FIG. 5D  also shows a fastener  510  (e.g., screw, bolt, etc. . . . ) used to affix the fiber distribution rack  400  to the rack mountable chassis. The front cable guide  520  has a radius end on both ends. This avoids sharp edges which could damage the fiber cable either by cutting it or by causing an excessive bend in the fiber cable. The radius end is designed to allow a fiber cable laying across it to not bend past an acceptable bend radius, thus minimizing any bend loss created in the fiber cable. In addition to the radius ends, the front cable guide  520  includes a series of fiber cable retention clips  530 . The fiber cable retention clips  530  hold the fiber cables in a way that helps reduce fiber cable density near the splitter modules  300 . This is accomplished by holding the fiber cable near the front edge of the front cable guide  520  until the fiber cable is approximately in-line with the splitter module  300  that it is to connect to. Once in-line with the splitter module  300  where the connection is to be made, the fiber cable is routed towards the splitter module  300 . 
         [0034]      FIG. 6A  depicts a fiber distribution rack  400  with full installation of splitter modules  300  and showing fiber cable  610  routing and connections  620 . The fully assembled, fully connected fiber distribution rack  600  is illustrative of the organized and lower fiber density design of an embodiment of the present invention. In an embodiment of the invention, a fiber distribution rack  400 , is mountable via fasteners  510  to a chassis. In at least one embodiment of the invention, the fiber distribution rack  400  can be loaded with up to fifteen (15) splitter modules  300 , wherein each can be affixed to the fiber distribution rack  400  via a pair of fasteners  340 . 
         [0035]    Unlike previous designs, fiber cable  610  can be routed towards the splitter modules  300  from either side of the fiber distribution rack  400 . This approximately halves the fiber cable  610  load handled by each side of the fiber distribution system. This feature helps eliminate high density fiber issues and allows for better manageability of the fiber cables  610 . Each fiber cable  610  has a connector  620  which engages a SC adapter  350  which is part of the splitter module  300 . The design of the splitter modules  300  and SC adapters  350  allow for straight forward connection without having to remove modules or panels, or worry about having to reroute or un-route fiber cables  610  through the rear of the fiber distribution system. In at least one embodiment, entire splitter modules  300  can be disconnected (maximum of six connections) and removed without causing any fiber cable  610  management issues or requiring any complex installation know-how. Reinstallation is no different, very easy and very simple. As can be seen in  FIG. 6A , the fiber cables  610  are routed from both sides of the fiber distribution rack  400 , resting along the radius of the front cable guide  520  and kept near the front edge of the front cable guide  520  by the fiber cable retention clips  530  until the fiber cable  610  arrives at its respective splitter module  300 . At that point it is routed inward to the corresponding SC adapter  350  on the splitter module  300 . This set-up allows for a clean, neat, and low-density fiber cable  610  routing, thereby reducing installation complexity and minimizing the chance of fiber cable  610  damage. 
         [0036]      FIG. 6B  depicts an alternative embodiment for fiber cable  610  routing. In this embodiment, the front cable guide  520  includes a plurality of cable guide slots  630  that increase in length relative to their location from the ends of the front cable guide  520 . The cable guide slots  630  in the center of the front cable guide  520  are longer than the cable guide slots  630  on each end of the front cable guide  520 . As can be seen in  FIG. 6B , the fiber cables  610  are routed from both sides of the fiber distribution rack  400  under the front cable guide  520  until the fiber cable  601  arrives at its respective splitter module  300 . At that point the fiber cable  610  is routed through a cable guide slot  630  and to a corresponding SC adapter  350  on the splitter module  300 . 
         [0037]      FIG. 7  illustrates an entire fiber distribution chassis  700 , with a plurality of fiber distribution racks  400 , each housing a plurality of splitter modules  300 . An additional feature illustrated in  FIG. 7  is the series of spools  710  located along either side of the fiber distribution racks  400 . These spools  710  are very similar to the spools  130  shown in  FIG. 1 . There is not necessarily a pair of spools  710  for every fiber distribution rack  400 . In an embodiment of the present invention, there is one pair of spools  710  for every three fiber distribution racks  400 . The spools  710  receive fiber cable  610  which is routed in from both sides of the chassis and are used to route/support the fiber cable  610  before it is routed to a front cable guide  520  for connection to a splitter module  300 . Unlike previous designs which used only a single series of spools  710  on one side of the fiber distribution system  700 , an embodiment of the present invention has a series of spools  710  on either side of the fiber distribution racks  400 . Having a pair of spools decreases the number of fiber cables  610  which are routed to each side, thereby reducing the fiber cable  610  density which makes the system more manageable, decreases complexity, and reduces the opportunity for cable damage due to inadvertent cable bend. The use of double spools  710  (i.e., opposing pairs) also means that fiber cable  610  length can be reduced on some fiber cable routes. 
         [0038]      FIG. 8  is a rear perspective of the fiber distribution chassis of  FIG. 7  showing the cable entrance  820  and a rear cable guide  810  as well as showing a rear perspective of the splitter modules  300  fully installed in the fiber distribution racks  400 . This perspective illustrates the simplicity of the embodiments of the fiber distribution system of this invention. In at least one embodiment, the fiber cables  610  are routed through one of two cable entrances  820  where they continue downward. The fiber cables  610  then exit onto a rear cable guide  810  when the fiber cables  610  have reached the level of the appropriate fiber distribution rack  400 . From the rear cable guide  810 , which also contains radius ends, the fiber cables  610  are routed onto one or more of a plurality of spools  710  and then onto a front cable guide  520 , where they make there way to a connection with one of the plurality of SC adapters  350  which are located on the face flange  330  of each splitter module  300 . 
         [0039]    It has been shown that the present invention provides a less complex, easier to install, smaller, lighter, and less costly fiber distribution system (FDS). 
         [0040]    While an illustrative embodiment of the invention has been described above, it is, of course, understood that various modifications will be apparent to those of ordinary skill in the art. Such modifications are within the spirit and scope of the invention, which is limited and defined only by the appended claims.