Abstract:
A device, system, and method for managing slack in fiber optic cables that are connected from a fiber distribution shelf to a fiber termination shelf in a controlled environment vault are described. Individual fiber optic cables are bundled together and placed in a sheath. The ends of the individual fiber optic cables extend past the sheath and are staggered to correspond to ports in the fiber distribution shelf.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to an arrangement of fiber optic cables that are utilized for transmitting signals in a telecommunications network. More particularly, the present invention relates to reducing the slack and routing complexity that normally result when equipment is coupled using the cables. 
     2. Background of the Invention 
     Currently, signals transmitted from a central office to a subscriber in a telecommunications network undergo several transformations. The signals are transmitted from the central office as optical signals that travel along fiber optic cables. The optical signals are received at a CEV (“controlled environment vault”) where they are converted to electrical signals that are transmitted over copper wires and then are converted back to optical signals before being transmitted to the subscriber. 
     FIG. 1 is a schematic diagram of a conventional CEV  103  within a telecommunications system. CEVs house electronic equipment that converts the signals and are typically located about ten (10) to twelve (12) feet deep underground. The signals are temporarily converted to electrical signals for the purpose of amplifying or otherwise adjusting them. Typically, fiber optic cables  101  enter the CEV from a central office  100  and connect to multiplexers  102 . Multiplexers  102  convert the optical signals into electrical signals. Jumper cables  106  are wired from multiplexers  102  to an equipment bay assembly shelf  112 , within an equipment bay assembly  113 , which provides electrical signal cross-connects and separates the respective signals into a dial tone. Fiber optic cables  108  connect the equipment bay assembly shelf  112  to a fiber termination shelf  114 . The fiber termination shelf  114  is a cross-connect, and ultimately connects the fiber optic cables to subscribers  116 . A ladder, pump, and battery supply (not enumerated in FIG. 1) are also contained in the CEV. 
     FIG. 2 is a schematic diagram illustrating a typical configuration of an equipment bay assembly  113 . An example of an equipment bay assembly system is the DISC*S MX Bay Assembly manufactured by Marconi Corporation PLC. Fiber optic cables  205  are coupled to a fiber distribution shelf, MDS # 1   204 , from common shelf  112 . There are twenty-eight (28) T-1 lines coupled to the common shelf  112 , carrying twenty-four (24) telephone lines between the common shelf and MDS # 1 . Although not shown in the present embodiment, fiber optic cables may also be connected to MDS # 2   206 . 
     FIG. 3 is a depiction of a fiber distribution shelf  204  illustrating how fiber optic cables  205  are attached. Fiber distribution shelf  204  has fourteen (14) removable cards (not all shown)  304   a - 304   n  each having four (4) fiber ports. Cards  304  fit into slots (not shown) in a housing of fiber distribution shelf  204 . The fiber ports are color-coded and numbered according to a well-known universal color code. (according to this color code, blue is “1”, orange is “2”, green is “3” and brown is “4”). Fiber cables  205  are quad jumper cables, such that each cable consists of four (4) separate cables that are grouped together. Therefore for each card, the cable has four (4) ends, one of each color, grouped together to form a single cable. 
     As shown in FIG. 4, each of the  14  fiber optic cables  205  are then connected from one of the cards in the fiber distribution shelf  204  to fiber termination shelf LGX  402 . From fiber termination shelf  402 , signals are ultimately transmitted to a neighborhood to supply service to respective subscribers. 
     The conventional configuration of fiber optic cables within a CEV as described above is associated with several difficulties and inefficiencies. Particularly, while each card  304  can accommodate 4 fiber optic cables, each handling 24 telephone lines for a total of  1344  lines in fiber distribution shelf  204 , common shelf  112  can only accommodate 28 T-1 cables, or 672 telephone lines. As a result, only two (2) of the four (4) available ports in each card are used. Although equipment bay assemblies, such as future releases of the MX system may use a second fiber distribution shelf (MDS #  2 , shown as  206  in FIG.  2 ), it cannot concurrently be used to connect to the fiber termination shelf  402 . As shown in FIG. 5, the unused cables are instead loosely hanging by the equipment bay assembly. Since all of the cables are the same length, there is slack  500 , which sometimes causes damage to the cables. 
     FIGS. 6 a  and  6   b  illustrate conventional means for handling slack in fiber optic cables  602  that couple the fiber distribution shelf  204  to the fiber termination shelf  402 . As shown in FIG. 6 a,  a fiber management device  600  is placed on top of equipment bay assembly  113 , and excess cable  602  is contained within the device  600 . However, device  600  is expensive, and it also is not specifically tailored to particular equipment bay assemblies. Depending on the length of the excess cable, it may be difficult to install the device  600 . 
     FIG. 6 b  depicts an arrangement of cables connecting the fiber distribution shelf to the fiber termination shelf that are looped in order to reduce the amount of excess cable that is hanging loosely. As shown, the excess cable  602  is simply looped and placed aside. Because the space in which the cables are looped is narrow, the looping can cause sharp bends  604 . Such sharp bends may damage or break fiber optic cables, or otherwise affect the transmission characteristics of the cables, necessitating their replacement. 
     FIG. 7 illustrates a conventional connection of quad jumpers  205  to fiber distribution shelf  204 . Because the ends of the cables are all the same length and there is a separate cable for each group of four (4) jacks on each card, it is difficult to efficiently wire the ends of the cables into the ports in the cards  304  of the fiber distribution shelf  204  to reduce slack. Moreover, there are no indicator labels on the cable ends to assist one installing the cables. In addition, there is a separate cable for each group of four (4) jacks on each card. 
     As can be seen, conventional cable wiring or routing paradigms lead to a mass of cables for which slack is not efficiently removed. As a result, cables frequently obstruct passage in the close confines of the CEVs or are susceptible to damage or breakage. 
     SUMMARY OF THE INVENTION 
     The present invention solves at least the foregoing problems in the art by providing a cost-effective device, system, and method for managing slack in fiber optic cables. The slack management technique of the present invention is more cost effective and provides more protection for the cable than in conventional systems. 
     In the present invention, individual fiber optic cables are bundled together and placed in a sheath. The ends of the individual fiber optic cables extend past the sheath and are staggered on one end to correspond to ports on a shelf on an equipment bay assembly while on the other end, the cables are the same length to accommodate a variety of fiber termination shelves. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of the interconnection of a conventional CEV in a telecommunications network. 
     FIG. 2 is a schematic diagram of an exemplary equipment bay assembly. 
     FIG. 3 depicts a conventional fiber distribution shelf in an exemplary equipment bay assembly as in FIG.  2 . 
     FIG. 4 is a schematic diagram of the equipment bay assembly in FIG. 2, illustrating a connection of fiber optic cables. 
     FIG. 5 depicts an exemplary equipment bay assembly connected to a fiber termination shelf utilizing a conventional arrangement of fiber optic cables. 
     FIG. 6 a  is a schematic diagram of a conventional apparatus for handling slack of a fiber optic cables in a CEV. 
     FIG. 6 b  depicts another conventional arrangement for handling slack in a CEV. 
     FIG. 7 depicts conventional connections of the fiber optic cables to a fiber distribution shelf. 
     FIG. 8 a  is a schematic diagram of an apparatus for bundling cables according to an embodiment of the present invention. 
     FIG. 8 b  is chart of the measurements for an exemplary embodiment according to FIG. 8 a.    
     FIG. 9 depicts connections of the fiber optic cables to a fiber distribution shelf utilizing an apparatus for bundling cables according to FIG. 8 a.    
     FIG. 10 depicts a method to manage slack in an apparatus for bundling cables according to FIG. 8 a.    
     FIG. 11 depicts illustrating placement of an apparatus for bundling cables according to FIG. 8 a  in relation to the equipment bay assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 8 a  depicts a cable assembly that can be used to connect a fiber distribution shelf to a fiber termination shelf with reduced slack and increased protection for fiber optic cables, according to an embodiment of the present invention. The fiber optic cables run from the central office, ultimately to telecommunications subscribers, through a CEV, as shown in FIG.  1 . 
     In the embodiment illustrated in FIG. 8 a,  cable assembly  800  includes twenty-eight (“28”) fiber optic cables bundled together in groups of four. Depending on how many fiber jumpers the common shelf can handle, there will either be twenty-eight (“28”) or fifty-six (“56”) fiber optic cables coming into the CEV. If there are fifty-six (“56”) fiber optic cables entering the common shelf, then there will be two cable assemblies  800  for connection to the fiber distribution shelf. 
     The cable assembly  800  includes a cable  802  which acts as a protective sheath. In an exemplary embodiment, the cable  802  can be a 12 foot length 36-fiber MIC riser cable having a 0.6 inch diameter. The cable assembly  800  connects the fiber distribution shelf to the fiber termination shelf in the CEV. Since the distance between the fiber distribution shelf and fiber termination shelf varies, cable  802  can be manufactured to be an appropriate length for the CEV in which the cable assembly will be used. 
     At either end of cable  802  is an epoxy plug  806 , which bundles together the fibers. At both ends  808  and  810  of the epoxy plugs  806 , the cable branches out into seven bundles (for clarity, only four bundles  814 ,  815 ,  816 , and  817  are shown at end  808  and only four bundles  818 ,  819 ,  820 , and  821  are shown at end  810 ), each having four cables (as shown by  817   a - 817   d  for bundle  817 ). The cables have connectors  812  on the ends. 
     On the end  808  that connects to the cards in the fiber distribution shelf, the cables  814 - 817  are staggered in length. The ports in fiber distribution shelf cards are engineered to be at a standard distance, and accordingly, the connectors  812  that are connected to the fiber distribution shelf can be staggered to match the configuration of the fiber distribution shelf. Although not shown in FIG. 8 a,  in the exemplary embodiment the cables  814 - 821  are numbered  1 - 28  and have connectors  812  on the ends to permit them to be wired into the fiber distribution shelf. Each bundle of four wires has spiral wrap  804  that extends, for example, six inches from the epoxy plug  806 . The spiral wrap  804  maintains the bundles of four cables grouped together. Cables such as  817  plug into the left side of the fiber distribution shelf, and are therefore shorter than cables such as  814 , that plug into the right side of the fiber distribution shelf. Thus, the cable lengths are staggered in length to be adaptively fitted to the respective connection on the fiber distribution shelf 
     On the end that connects into the fiber termination shelf, the cables at end  810  (i.e. cables  818 ,  819 ,  820 , and  821 ) are all the same length, since there are a variety of fiber termination shelves that may be used in a CEV, and the distance between the fiber distribution shelf and fiber termination shelf may differ. Therefore, cables at end  810  need to have a minimum amount of slack to allow for these differences. In the exemplary embodiment shown, the length of the cables at end  810  on the fiber termination shelf side is approximately equal to the average length of the cables  808  on the fiber distribution shelf side. 
     FIG. 8 b  is a chart illustrating the lengths of the cable ends in an exemplary embodiment. For each group of four cables on the MX card end, there are two cables that are the same length (“1” and “4”, for example), one cable that is comparatively two inches shorter (“2”, for example) and one cable that is comparatively two inches longer (“5”, for example). As can be seen in the graph, the cables are progressively longer. The cables (all 28 of them) at the fiber termination shelf end are all the same length, for example, 21 inches. Although not shown in FIG. 8 a,  the cables can be numbered to facilitate installation. 
     FIG. 9 illustrates that the staggered length cable end  808  creates less slack because the cables are exactly the length necessary to connect to the fiber distribution shelf  204 . Also shown in FIG. 9 is how the epoxy plug  806  can be placed in a more discrete location to remove some of the excess cable. 
     As shown in FIG. 10, on the fiber termination shelf side there will be a minimum amount of slack because the cables are not cut to the exact length necessary. However, the cable assembly of the present invention can be formed into a loop  1000  to be less intrusive. For example, the excess can be attached to the back of the bay assembly so that it is out of the way and a hook (not shown) can be used to secure the loop  1000 . Once the cables are wired, the assembly can be tied down by using rope  1002 . Typically, although the quad jumpers may need to be rearranged, the fiber distribution shelf and fiber termination shelf will not be moved, and so once the excess is placed out of the way, it may remain in this position. 
     FIG. 11 depicts the new fiber management system  800  placed to the side of the bay assembly and the fiber distribution shelf  204 , in a more convenient location. A comparison of FIG.  11  and FIG. 7, the conventional system, demonstrates the benefits of the new system. 
     The foregoing disclosure of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
     Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.