Abstract:
Optical ribbon cable fan-out device includes a top cover portion, a fan-out portion and a bottom portion formed as a unitary body. The fan-out portion has an array of guides housing individual fibers of the optical ribbon cable. The top cover portion and bottom cover portion are connected respectively to the fan-out portion by first and second hinges. The top cover portion and the bottom cover portion each have a plate projecting respectively therefrom to secure a ribbon cable in an axis extending longitudinally through the fan-out apparatus. The fan-out portion is so configured that a first portion of the arrayed guides is co-linear with the axis, a second portion of the arrayed guides is above the axis and a third of the arrayed guides is below the axis. The fan-out apparatus defines pathways for individual optical fibers having a bend radius of at least approximately 1.5 inches.

Description:
FIELD OF INVENTION  
         [0001]    The present invention generally relates to optical fiber closures and, more particularly, to an optical fiber closure having improved optical fiber capacity and insertion loss characteristics.  
         BACKGROUND OF INVENTION  
         [0002]    Optical communications refer to the medium and the technology associated with the transmission of information as light pulses. Many applications utilize an optical fiber network to establish optical communications between network locations. In order to enable optical communication and the flow of optical signals between network locations, various interconnections must be established between different optical fibers.  
           [0003]    [0003]FIG. 1 depicts a fan-out device  100  associated with the prior art for handling optical fibers. Specifically, fan-out device  100  accepts a ribbon cable  102  which comprises a plurality of individual optical fibers  104 . Such devices are used to separate the individual fibers  104  prior to their terminations onto optical connectors. A typical ribbon cable consists of 12 individual fibers. As these individual fibers are separated, they are subject to bending. The bend radius R B  of the fibers is an important characteristic of the fan-out device because it corresponds to the degree of “light leakage” in each of the individual fibers. That is, as light propagates through an individual fiber, a portion of the light will travel beyond the boundaries of the fiber if R B  is too small (corresponding to an angle of incidence of the light upon the fiber core that is greater than the critical angle for total internal reflection of the light). Current designs have R B  of approximately 0.5 inches which results in unnecessarily high leakage of light and optical signal degradation.  
           [0004]    Additionally, current fan-out devices comprise a two piece construction with an epoxy seal. Specifically, upper portion  106  and lower portion  108  are joined to protect the individual fibers  104  as they fan out. The epoxy is utilized to maintain an R B  so that if a fiber is pulled, it will not kink and generate microbends. If this epoxy cures while the fiber is not set to the correct R B , optical losses will result from this condition also. Moreover, as the upper portion  106  and lower portion  108  are joined, there may be alignment errors that cause severing or crimping of one of more of the individual fibers.  
         SUMMARY OF THE INVENTION  
         [0005]    These and other deficiencies of the prior art are overcome according to the principles of the invention in an apparatus for fanning out an optical ribbon cable having a top cover portion, a fan-out portion and a bottom portion such that the three portions are formed as a unitary body with the fan-out portion having a stacked array of optical fiber guides for housing individual fibers of the optical ribbon cable. The top cover portion is connected to the fan-out portion by a first hinge and the bottom cover portion is connected to the fan-out portion by a second hinge. In one embodiment, the first hinge and second hinge are of the same material as the top cover portion and bottom cover portion. The material of which the apparatus is comprised is a substantially non-opaque material and in one embodiment on the invention is a polymer 12-based material.  
           [0006]    A part of the fan-out portion transitions to a hook member. Additionally, a part of the top cover portion transitions to a partial tang and the bottom cover portion transitions to a partial tang to jointly define a complete tang. The hook member and complete tang facilitate securing the apparatus to a support structure.  
           [0007]    The top cover portion has a plate projecting perpendicularly from a top cover portion front face and the bottom cover portion has a plate projecting perpendicularly from a bottom cover portion front face. The two plates secure a ribbon cable in an axis extending longitudinally through the fan-out apparatus. The fan-out portion of the apparatus is so configured that a first portion of the arrayed guides is co-linear with the longitudinally extending axis, a second portion of the arrayed guides is above the longitudinally extending axis and a third of the arrayed guides is below the longitudinally extending axis. The fan-out portion has a body having a front face and a rear face. The arrayed guides traverse longitudinally through the fan-out portion from the front face to the rear face. In one embodiment of the invention, the arrayed guides are in the form of a 3×8 matrix in the body. The arrayed guides are tapered such a width of each of said guides at the front face is wider than a width at the rear face. The fan-out apparatus also has an apparatus front face wherein the arrayed guides define pathways for individual optical fibers disposed from said apparatus front face to said fan-out portion rear face having a bend radius of at least approximately 1.5 inches. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:  
         [0009]    [0009]FIG. 1 depicts a fan-out device associated with the prior art;  
         [0010]    [0010]FIG. 2 depicts an isometric view of a fan-out device of the subject invention detailing the rear of the device;  
         [0011]    [0011]FIG. 3 depicts an isometric view of the fan-out device of FIG. 2 with the top cover portion partially open;  
         [0012]    [0012]FIG. 4 depicts an isometric view of the fan-out device of FIG. 2 with the top cover fully open; and  
         [0013]    [0013]FIG. 5 depicts an isometric view of the fan-out device of the subject invention detailing the front of the device. 
     
    
       [0014]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    [0015]FIG. 2 depicts an isometric view of a fan-out device  200  in accordance with the subject invention. The fan-out device  200  is capable of receiving a ribbon cable  102 , separating out a plurality of optical fibers  104  (depicted as encased in buffer tubes) comprising said ribbon cable and presenting them in an organized fashion. This condition permits individual manipulation of each of said plurality of optical fibers  104  in such a manner so as to decrease losses associated with excessive bending of the individual fibers. Additionally, the subject invention is capable of handling larger numbers of fibers than previously realizable.  
         [0016]    The fan-out device  200  comprises a top cover portion  202 , a fan-out portion  204  and a bottom cover portion  206 . The top cover portion  202  and bottom cover portion  206  are substantially identical in length to provide an enclosure (explained in greater detail below) for receiving the ribbon cable  102  and fanning out the plurality of individual fibers  104  in the ribbon cable  102 . The fan-out device  200 , and more specifically the portions comprising same, are fabricated from a polymer- 12  based material. In one embodiment, the fan-out device  200  is fabricated from Grilamid which is a clear plastic material manufactured and sold by k-Mac Plastics of Kentwood, Mich. One skilled in the art will realize that other types of materials are suitable for the application. Such materials are, in one example, non-opaque and relatively durable (so as to withstand handling and installation into supporting frameworks and opening and closing of the device). For example, if the material is substantially transparent, the material is quite suitable for the purposes of visible examination of the fibers. If the material is translucent, the material should be reasonably visibly clear so as to allow viewing of the fibers as there are various degrees of translucency. It will also be realized that either the top cover portion  202  or bottom cover portion  206  or both components maybe be non-opaque depending upon the specific application or manufacturing process.  
         [0017]    The top cover portion  202  has a rear section  214   1 , and a front section  216   1 . Similarly, bottom cover portion  206  has a rear section  214   2  and a front section  216   2 . The top cover portion  202  is connected to the fan-out portion  204  at the top cover rear section  214   1 , via top hinge  218 . Similarly, the bottom cover  206  is attached to fan-out portion  204  at the bottom cover rear section  214   2  via bottom hinge  220 . A double-hinged assembly  218 / 220  is thus created between the top cover portion  204 , fan-out portion  204  and bottom cover portion  206  by joining these pieces in the manner prescribed. In each instance, top hinge  218  and bottom hinge  220  are relatively thin areas of material of which the fan-out device  200  is constructed. One skilled in the art will understand to make top  30  hinge  218  and bottom hinge  220  substantially thin enough so as to provide hinged motion between the top cover portion  202 , fan-out portion  204  and bottom cover portion  206  yet remain durable enough to maintain structural integrity of the overall device. It will also be understood to one skilled in the art that a thin layer material version of the fan-out device  200  is not the only way hinged attachment of these components can be made and that other suitable materials or methods of attachment are possible.  
         [0018]    The bottom cover portion  206  further comprises a plurality of perpendicularly extending tangs  208   1  and  208   2 . Specifically, and in one embodiment, first tang  208   1  extends upward from first bottom cover portion side  222   1  proximate front section  216   2 . Similarly, second tang  208   2  extends upward from second bottom cover portion side  222   2  (obscured in FIG. 2 but seen in FIG. 5) proximate front section  216   2 . Top cover portion  202  comprises a plurality of notches  226   1  and  226   2  for communicating with tangs  208   1  and  208   2  respectively. Specifically, first top cover notch  226   1  is recessed in first top cover side  224   1 . Similarly, second top cover notch  226   2  is recessed in second side  224   2  on the top cover portion  202  (detailed in FIG. 5). Each of said tang/notch combination secures the top cover portion  202  to the bottom cover portion  206 .  
         [0019]    The fan-out portion  204  comprises a rear face  210  that defines the rear of the fan-out device  200 . The rear face  210  is the point at which the individual fibers are first presented as they exit the fan-out device  200 . The rear face  210  transitions into a hook element  212 . The hook element  212  facilitates securing the fan-out device  200  to a framework for stabilizing same and the fibers contained therein.  
         [0020]    [0020]FIG. 3 depicts an isometric view of the fan-out device  200  with the top cover portion  202  partially open. From this vantage point, it is seen that first top cover notch  226   1  further comprises a first ridge  302   1  that first tang  208   1  contacts until locking into place when the top cover portion  202  is closed. Similarly, second top cover notch  226   2  further comprises a second ridge  302   2 , partially obscured, that second tang  208   2  contacts until locking into place.  
         [0021]    With the top cover portion  202  partially open, the internal configuration of the fan-out device  200  is more readily seen. Specifically, top cover portion  202 , fan-out portion  204  and bottom cover portion  206  define a two-stage internal cavity  306 / 308 . Specifically, a first internal cavity  306  houses the fan-out portion  204  and allows individual fibers  104  of the ribbon cable  102  to be spread apart. Second cavity  308  is forward of first cavity  306  and is smaller in volume so as to accept the ribbon cable  102  without undue gap or spacing between it and the fan-out device (thereby preventing undue bending or flexing of the ribbon cable which can cause breakage) as well as establishing an axis A for which the individual fibers can be referenced against. To further stabilize the ribbon cable  102  as it enters the second recess  308 , a stabilizing block  310  is disposed on top of the ribbon cable  102 . When top cover portion  204  is hinged closed over bottom portion  206 , top portion  202  will slightly compress stabilizer block  310  so as to stabilize the ribbon cable  102  in the fan-out device  200 .  
         [0022]    [0022]FIG. 4 depicts an isometric view of the fan-out device  200  with the top cover portion  202  fully open. In FIG. 4, it should be noted that the ribbon cable  102  and individual fibers  104  are not shown so as to facilitate viewing of the fan-out device  200 . Specifically, with the top cover portion  202  fully open, the fan-out portion  204  is more readily seen and accessed. The fan-out portion  204  comprises a fiber holding body  402 . The holding body  402  is substantially a solid block having a plurality of individual fiber optic cable guides  404  extending there through. Specifically, the guides  404  extend from a front face  406  of the body  402  to the rear face  210 . The guides  404  are flared out slightly at the front face  406  to facilitate insertion of the individual fibers  104 . In other words, a width of the guides at the front face  406  is wider than a width of the guides at the rear face  210 . The individual guides  404  are arranged in a stacked layout. In one embodiment of the invention, there are 24 guides  404  arranged in a matrix. One example of the 24 guide matrix is 8 columns by 3 rows. It will be understood to those skilled in the art that other types of arrangements are possible (i.e., any n×m matrix that is suitable for handling the number of individual fibers  104 , an offset or staggered layout where the guides  404  in one row are not aligned with a row of guides directly above or below and the like) and the particularly disclosed embodiment is not the sole possible arrangement of guides  404 . To minimize undue bending and flexing of the individual fibers as they approach the block  402 , the fan-out device  200  is designed in such a manner that when fully closed (as shown in either FIGS.  2  or  5 ), a center row of guides  404   c  will fall substantially within the axis A that the ribbon cable  102  is aligned.  
         [0023]    Body  402  is further provided with a first recess  410   1  and a second recess  410   2  disposed on opposite sides of said body  402  at the front face  406 . Additionally, first body tang  412   1  and second body tang  412   2  extend perpendicularly from bottom cover portion  206  in a similar fashion as first tang  208   1  and second tang  208   2  described earlier. As the top cover portion  202  is hinged over and closes upon bottom cover portion  206 , the body  402 , which is integral with hinge portion  204 , comes into contact with the first body tang  412   1  and second body tang  412   2  in such a manner so as to positively lock the body  402  in place when the first body tang  412   1  engages first recess  410   1  and second body tang  412   2  engages second recess  410   2 .  
         [0024]    [0024]FIG. 5 depicts an isometric view of the fan-out device  200  of the subject invention detailing the front of the device. The top cover portion  202  further comprises a front face  502 . Similarly, the bottom cover portion  206  comprises a front face  504 . The respective front faces  502  and  504  are substantially within the same plane. The top cover portion front face  502  includes a first tang portion  506   1  at one end of its face. Similarly, bottom portion cover face  504  includes a second tang portion  506   2  at one end. Collectively, front face tangs  506   1  and  506   2  form a single complete tang  506  for securing the fan-out device  200  into a board, frame or other type of frame component within the fiber optic system. Specifically, the tang  506  provides a releasable locking mechanism to secure the fan-out device  200  and allow for a hinged motion of same about hook member  212 .  
         [0025]    Top front face  502  further includes a top plate  508   1  projecting perpendicularly from front face  502 . Similarly, bottom front face  504  includes a bottom plate  508   2  projecting perpendicularly from bottom portion face of  504 . Plates  508   1  and  508   2  close upon and clamp down the incoming ribbon cable  102 . This arrangement secures the ribbon cable  102  in the axis A and prevents undue flexing or bending of such as it approaches the fan-out device  200 .  
         [0026]    The advantages of the subject invention are readily realized. Specifically, the unitary construction of the device  200  facilitates handling (i.e., opening and closing) of the device  200  without the problem of misalignment of the top cover portion and bottom cover portion. The total number of molds to create the device (and parts resulting therefrom) is reduced from three to one. The increased length of the housing and configuration of the individual fiber optic guides  404  increase the R B  to approximately 1.5 inches which meets the requirements for the fiber optic cables protected therein. In other words, pathways for the individual fibers  104  are defined in the two cavities  306  and  308  and at the front face  404  of the fan-out body  402  such that the R B  is at the much more acceptable value. Accordingly, the device results in a very low loss characteristic from light leakage. The non-opaque material used for to fabricate the device facilitates visual inspection without having to handle the device of the fibers contained therein. Lastly, the design of the device allows for double the amount of individual fibers to be handled per device in comparison to the prior art. That is, a holding body as described contains an array of 24 individual guides for receiving 24 individual fibers as opposed to the current designs that only hold 12 fibers. The latest ribbon cables having 24 individual fibers can thus be integrated into a system and handled with ease by the subject invention. The design also allows flexibility in planning an optical network as any number of individual fibers between 3 and 24 can be properly fanned out.  
         [0027]    Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.