Abstract:
A fiber distribution terminal for use in an environmentally sealed enclosure can include a rotatable spool for housing input fiber cable. The spool is configured to be mounted in the environmentally sealed enclosure. The fiber distribution terminal can also include an adapter pack that secures the connections between fibers of the input fiber cable and fibers of the output fiber cable. The fiber distribution terminal can include an adapter plate that guides the routing of both the input and output fiber cables internal to the enclosure. The fiber distribution terminal can also include a spool lock that can direct the cable routing to a first side or a second side of the fiber distribution terminal.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/347,624, filed Dec. 31, 2008, which is hereby incorporated herein in its entirety by reference hereto. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a fiber distribution terminal having an internal spool for storing and protecting fiber cable. 
         [0004]    2. Background 
         [0005]    A Fiber Distribution Terminal (FDT) is used to interconnect multiple fibers, typically originating from a common point, and distributed to multiple different locations with output fiber cables. A FDT typically comprises an enclosure wherein connections are made between a larger multi-fiber bundle input cable and individual output fiber cables. The typical application configuration for the use of an FDT is in buildings such as multi-unit residences or commercial/office buildings. There could be a single FDT per building or perhaps one or more per floor or any combination in between depending on the fiber connection needs and capacity of the building. 
         [0006]    One recurring issue faced when dealing with the installation of FDTs is how much input fiber is required to connect the FDT to some common point, which is often outdoors where the connections to the larger fiber networks (e.g., city wide fiber network) are made. The common point could also be within the same building, perhaps on another floor or in the basement of the building. No matter the location of the common point, the issue remains that it is often necessary to physically locate the FDT before the approximate required length of fiber cable is known. Issues involved with not knowing the required length of fiber cable could present themselves in at least two ways. First, it might be necessary to approximate and prepare a length of fiber cable before installation of the FDT occurs. If the approximation is too short then the connection to the FDT cannot be made without further fiber cable splices or another length of fiber cable will have to be obtained. Conversely, if the approximation is too long, then the excess slack of fiber cable will have to be stored somewhere along the length of fiber cable. This creates the possibility of introducing unwanted bends and thus unwanted bend loss into the fiber cable path. Second, it might be necessary to relocate the FDT so that the chosen or available fiber cable length is approximately correct, which could mean placing the FDT in an undesirable location. These problems arise because there is presently no safe way to store excess fiber cable after installation nor feed fiber cable from an installed FDT. Another problem is that there is no convenient way to store the input fiber cable prior to installation of the FDT. 
         [0007]    It would be convenient to affix the box to its permanent location and to make the input fiber cable connections before having to connect the input fiber cable to the common point. Presently this is not possible. There are FDTs available that include an external spool of fiber cable but they do not allow the FDT enclosure to be affixed to its permanent location because the enclosure must rotate with the external spool of fiber cable. This also prevents the installer from making the input fiber connections to the adapter pack prior to connection of the input fiber cable. 
         [0008]    Available FDTs have only one output direction for the input and output fiber cables that are entering and exiting the FDT enclosure. This ensures that the routing of the cables internal to the enclosure is always oriented in the same direction. But this often makes the external installation difficult and the routing of cables external to the FDT enclosure cumbersome. This can occur in situations where the external fiber routing needs to go to a higher floor and the FDT only has fiber cable outputs to the bottom of the enclosure (relative to the mounting orientation), meaning that the fiber cables must make a 180 degree turn after they leave the enclosure. This often results, especially with less experienced installers, in damage to the fiber cable, usually due to inadvertent bend loss. 
         [0009]    It is also important to protect the fiber cables when they are internal to the FDT enclosure. Typical enclosures contain connection blocks where the fibers of the larger input cable are individually matched to single output cables. Both the input and output cables are separately routed through the enclosure, with the installer having the responsibility of routing the fiber cables in such a way so as to avoid bends in the cable and thus bend loss. Installers, who may or may not be conscious of this responsibility, might not always appreciate the impact of their craftsmanship. Routing secured by cable ties or other more industrial type retaining clips could easily create inadvertent bends in the fiber cables, thus causing undesired loss of signal strength in the fiber cables. 
         [0010]    Therefore, it is desirable to have a FDT that conveniently stores fiber cable prior to installation and houses excess fiber cable after the input cable connection has been made. It is also desirable for the FDT to house the input fiber cable to output fiber cable connections and safely route the cables internal to the FDT enclosure to avoid bend loss while allowing the input and output fiber cables to enter/exit through either of two sides to the enclosure. 
       SUMMARY 
       [0011]    According to an embodiment of the invention, there is provided a fiber distribution terminal (FDT) including an environmentally sealed enclosure. The FDT has a spool for housing input fiber cables disposed in the enclosure and mounted for rotation therein. The FDT further comprises an adapter pack contained within the enclosure for securing connections between fibers of the input fiber cables and fibers of output fiber cables. The FDT also comprises an adapter plate contained within the enclosure for routing the input and the output fiber cables internal to the enclosure. 
         [0012]    In another embodiment of the invention, there is provided a FDT having an environmentally sealed enclosure with an internal spool, and adapter pack, and further including a spool lock which is configured to direct the cable routing to one of the first side or second side of the FDT. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    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: 
           [0014]      FIG. 1  depicts a multi-unit building which is a typical application situation for the use of a fiber distribution terminal (FDT); 
           [0015]      FIG. 2  is a cross-sectional view of one embodiment of the invention; 
           [0016]      FIG. 3  is an internal view (with the enclosure door open) showing the adapter plate cable routing and the adapter pack cable connections with the internal spool disposed beneath; 
           [0017]      FIG. 4  is an exploded view of the elements of a FDT; 
           [0018]      FIG. 5  depicts one of the output grommets capable of holding up to tour output cables; 
           [0019]      FIG. 6  is a cross-sectional view of the output fiber cable grommet of  FIG. 5  showing the different chambers internal to the grommet; and 
           [0020]      FIG. 7  depicts the input grommet capable of holding up to two, twelve fiber input fiber cables. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    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. 
         [0022]      FIG. 1  depicts a multi-unit building  100  according to one embodiment of the invention. The multi-unit building  100  includes separate units  120 , one or more of which have a necessity or desire to have fiber cable service in their unit. Each separate unit  120  typically only needs a single output fiber connection  112 , but a typical situation in a multi-unit building  100  would have some plurality if not the entire building needing or desiring the fiber cable service. The fiber cable provider will run a larger bundled input fiber  110  to the multi-unit building  100  where it is routed and connected through what is known as a fiber distribution terminal (FDT)  102 . The FDT is secured to an interior wall in the basement or a communication closet within the multi-unit building  100  via supplied mounting brackets  104  allowing the FDT  102  to be securely placed in order to protect the fiber cables which can be easily damaged if care is not taken in their placement, routing, and storage. The input fiber  110  is actually multiple fiber cables bundled together into a larger cable for easier routing to some central location. The input fiber  110  is inputted into the FDT  102 . Internal to the FDT  102 , the individual fiber cables that comprise the input cable  110  are separately connected to individual output cables  112 . Then each output fiber cable  112  is routed to a separate unit  120 , where the output fiber cable  112  can be connected to other equipment that is capable of translating the fiber cable signal into useful information. 
         [0023]      FIG. 2  is a cross-sectional view of one embodiment of the invention. The fiber distribution terminal  102  comprises several components. Because of the need to protect connections from environmental dangers, it is desired to house the components inside an environmentally sealed enclosure  200 . Internal to the enclosure  200  is a spool  202 , an adapter pack  206 , and an adapter plate  204 . The adapter plate  204  is coupled to and rotates with the spool  202 . As an addition to the adapter plate  204 , the enclosure  200  includes a set of fiber cable guides  230 . There are also locations on the enclosure  200  for passing the input  110  and output  112  cables through. These locations are filled and secured with an input grommet  210  and a set of output grommets  220 . 
         [0024]      FIG. 3 , is an internal view (with the enclosure door open) of FDT  102 . Additional components in  FIG. 3  that have not been previously disclosed are a spool lock  302 , a Splice Closure/Angled Physical Contact (SC/APC) adapter  310 , a handle  330 , an input plug  370 , and output plugs  360 . 
         [0025]    The spool  202  is used to house the input fiber cable  110  inside the enclosure  200 . The spool  202  is disposed internal to the enclosure in such a way that it is free to rotate inside the enclosure. The larger bundled fiber cable  110 , which is a single cable comprised of multiple (e.g., twelve fibers) individual fibers, is fed through an input grommet  210  in the enclosure  200 , and can be extended to the maximum storage capacity of the spool. In one embodiment the spool is capable of storing two 200 ft input fiber cables. If two input fiber cables are stored, they must be extended together. Because of the design of the FDT  102 , it is not practical to install the input fiber cable  110  after the FDT  102  has been assembled. Thus the FDT  102  is shipped with the input fiber cable  110  already installed on the spool  202 . Thus, the FDT  102  also serves as a shipping container for the spool  202  of input fiber cable  110 . 
         [0026]    The input grommet  210  which will be described in more detail below, is capable of housing two separate bundled input fiber cables  110  each containing multiple individual fiber cables. The input fiber cable  110  that is fed through the input grommet  210  is then connected via other fiber network components (not shown) to the larger fiber network (i.e., street connection or larger). The other end of the input fiber cable  110  is unbundled into the individual fiber cables which make up the larger input fiber cable  110 . Each individual fiber cable is then connected to an SC/APC adapter  310 . In at least one embodiment, the SC/APC adapter  310  allows for four individual cables to be connected per adapter  310 . The SC/APC adapters  310  are located using a series of adapter posts  340  at a central position internal to the FDT enclosure  200 . In at least one embodiment, there are six input side SC/APC adapters  310  and seven adapter posts  340  for positioning the adapters  310 . There are guidance slots  350  in the adapter plate  204  which provide a convenient and safe way to route the individual cables of the input fiber cables  110  from the spool  202  to the SC/APC adapters  310  located on the opposite side of the adapter plate  204 . In at least one embodiment, there are six guidance slots  350  so that four individual fiber cables of the input fiber cables  110  can be routed through each slot. 
         [0027]    The spool  202  can feed input fiber cable  110  through the input grommet  210  up to the maximum spool capacity. The input fiber cable  110  is then routed as needed and any excess input fiber cable  110  can be manually retracted onto the spool  202  through the input grommet  210  by turning the handle  330  internal to the enclosure. In an embodiment of the invention, excess input fiber cable  110  does not have to be stored outside of FDT  102 , but rather is safely re-spooled on to spool  202 . This helps avoid unnecessary damage such as bends or pinches of the input fiber cable  110  which can drastically reduce the signal quality that the input fiber cable  110  is capable of transmitting. 
         [0028]    One end of the output fiber cables  112  have a SC/APC adapter  310  mate so that the output fiber cables  112  can be coupled to the input fiber cables  110 . The end of the output fiber cable  112  to which the SC/APC adapter  310  is attached is the end that is internal to the FDT enclosure  200 . In at least one embodiment, the SC/APC adapter  310  allows for four individual cables to be connected per adapter  310 . The SC/APC adapter  310  on the output fiber cables  112  are kept organized and safely located using the same series of adapter posts  340  as the input side SC/APC adapter  310  used, which is located at a central position internal to the FDT enclosure  200 . The area where the input and output side SC/APC adapters  310  are coupled and held in place by the adapter posts  340  is collectively called the adapter pack  206 , and any reference to the adapter pack  206  is synonymous with at least one input/output coupled SC/APC adapter  310  pair held by the adapter posts  340 . The purpose of the adapter pack  206  being contained within the enclosure  200  is to secure the connections between independent fibers of the input fiber cable  110  and independent fiber cables of the output fiber cable  112 . In at least one embodiment, the adapter pack  206  comprises six mated pairs of SC/APC adapters  310  held in place by adapter post  340 . 
         [0029]    The output fiber cable  112  connections are routed from the adapter pack  206  through a series of guides  230  to the output grommets  220 . The guides  230  are part of the adapter plate  204  which is used for routing the output fiber cables  112  in a safe and organized manner internal to the enclosure. In one embodiment, the guides  230  are shaped structures coupled perpendicular to the plane of the adapter plate  204 . The guides  230  are designed with specific radii which do not allow the output fiber cable  112  placed against the guides to bend more than the output fiber cable  112  specification allows, thereby minimizing bend loss within the output fiber cables  112 . Thus, the guides  230  provide a convenient and organized way to route the output fiber cables  112  through the enclosure  200 . The guides  230  are designed to maintain the output fiber cable  112  signal integrity. The adapter plate  204  and guides  230  are sized such that up to 70 mm cable connection boots, which are sleeves usually made of a flexible material that add a layer of protection to the connector, and up to 4.8 mm diameter cables can be used. The adapter plate  204  and guides  230  are also sized such that the use of Splice On Connectors (SOC) is facilitated. A SOC eliminates the need for field polishing of fiber cables in order to terminate connections. In one embodiment, there are at least three sets of guides  230  so that the output fiber cables  112  can make two 90 degree turns and be fanned out in order to line-up the output fiber cables  112  with the output grommets  220 . However, more or less guides  230  may be needed based on the internal routing of the enclosure  200  and the bend tolerance specification of the particular output fiber cables  112  used. As mentioned above, the output fiber cables  112  are routed out of the enclosure  200  through output grommets  220 . The number of output grommets  220  depends on the number of output fiber cables  112  that are to be routed out of the enclosure  200 . In one embodiment, there are six output grommets  220  which each hold four output fiber cables  112 . 
         [0030]    As part of the adapter plate  204 , there is at least one spool lock  302 . The spool lock  302  is designed so that when engaged, it affixes the rotation of the spool  202  to a single position, impeding further rotation of the spool  202 . In an embodiment of the invention, the spool lock  302  is a sliding latch that engages a pair of tabs designed into the wall of the enclosure  200 . The introduction of the spool lock  302  allows the input and output fiber cables  110  and  112  of the FDT  102  to be routed from one of a plurality of sides of the enclosure  200 . This flexibility of fiber cable routing can drastically improve the craftsmanship of a fiber distribution terminal  102  installation. In order to maintain an environmentally sealed enclosure  200 , it is necessary to plug any of the input and output openings which are not used to route either input fiber cables  110  or output fiber cables  112 . To accomplish this, at least one input plug  370  which is identical in shape to input grommet  210  but is a single solid piece, and a plurality of output plugs  360  which are identical in shape to output grommets  220  but are solid pieces, are placed in the unused openings of the enclosure  200 . 
         [0031]      FIG. 4  is an exploded view of the elements of a FDT. No new parts are introduced, but the view allows for a better perspective of how the parts are coupled together. The adapter pack  206  is shown in  FIG. 4  as a pill shaped piece which fits between the adapter posts  340 ; however, the adapter pack  206  is actually the mated connection of at least one of the input fiber cables  110  and the output fiber cables  112 . Also note that in  FIG. 4  the handle  330  is not shown. The input fiber cables  100  and the output fiber cables  112  which constitute much of the full implementation of the FDT  102  are not shown in  FIG. 4  in order to make the main parts of the FDT  102  visible. The input and output plugs  360  and  370  are more visible in this perspective. 
         [0032]      FIG. 5  depicts one of the output grommets  220  capable of holding up to four output fiber cables  112 . Specific features of the output grommet  220  are a pair of channels  510  and  512 , at least one cylindrical void  504 , and a split  520  down the center of the axis which cuts through the cylindrical void  504  of the output grommet  220 . The channels are made such that they slip over protrusions fashioned in the enclosure  200  so that the output grommet  220  effectively seals itself in place, thereby keeping external environmental elements (e.g., water, bugs, etc. . . . ) out of the enclosure  200 . The output grommet  220  is designed for a tight fit against the enclosure  200  protrusions and has two sealing channels  510  and  520 , which increase the chance of creating an effective seal. This cylindrical void  504  provides an avenue for the output fiber cable  112  to be routed outside the enclosure. In one embodiment, the cylindrical void  504  can hold output fiber cables  112  in a range of sizes from 2 mm to 5 mm in diameter. The cylindrical void  504  is able to hold this range and also seal against components of the external environment because of internal output grommet  220  features which will be disclosed below in reference to  FIG. 6 . In at least one embodiment of the invention, the output grommet has four cylindrical voids  504  such that each grommet holds four output fiber cables  220 , There are a total of six output grommets  220 . 
         [0033]      FIG. 6  is a cross-sectional view of the output grommet  220  of  FIG. 5  showing two different chambers  610  and  612  internal to the grommet. Internal to each cylindrical void  504  there are ribs  620  which are manufactured in such a way that they block the path through the cylindrical void  504 , but are pliable enough that the ribs  620  migrate when an output fiber cable  112  is placed through cylindrical void  504  and seal around the output fiber cable  112 . In at least one embodiment, the output grommet  220  is designed with three such ribs  620 . This creates two void regions within the output grommet  220  which are described as chambers  610  and  620 . These chambers  610  and  620  can then be filled, if desired, with a sealing material to further ensure that an environmental seal is made between the environmental side of the output grommet  220  and the enclosure side of the output grommet  220 . The output fiber cables  112  are placed into the output grommet  220  by forcing the two halves of the output grommet  220  apart at the axis split  520 . Then, an output fiber cable  112  can be placed into one cylindrical void  504 . After which the two halves of the output grommet  220  can be allowed to spring back together. The at least one rib  620  is pliable enough but yet encompasses the output fiber cable  112  such that as small as a 2 mm fiber cable and as large as a 5 mm fiber cable are locked in place and an environmental seal is created around the fiber cable without damaging the fiber cable. 
         [0034]      FIG. 7  depicts the input grommet  210  capable of holding up to two, twelve fiber input cables  110 . The input grommet  210  features a mounting channel  730 , a split  720 , and at least one input cable void  710 . These features are almost identical to those of the output grommet  220  described above with reference to  FIGS. 5 and 6 . In at least one embodiment, the difference is that the input grommet  210  has only one channel which helps seal against the wall of the enclosure  200  at the input grommet cutout. Otherwise, the void  710 , ribs (not shown), and chambers (not shown) behave in the same manner as the corresponding parts of the output grommet  220 . The input fiber cable  110  is locked into position by the input grommet  210  while under typical stationary tension. However, the input grommet  210  is designed such that an installer can feed input fiber cable  110  through the installed input grommet  210  from the spool  202  and also retract the input fiber cable  110  back onto the spool  202  through the input grommet  210  without damaging the input fiber cable  110 . 
         [0035]    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.