Abstract:
This invention provides an apparatus and method for a high performance, flexible optical fiber furcation assembly that minimizes bending in the optical fibers throughout the life of the furcation assembly. The furcation assembly includes a flexible furcation body having a passageway with a first end and an opposed second end, the first end for receiving a fiber optic cable and the second end for routing a furcated leg, and holding material for flexibly securing and supporting the fiber optic cable and the furcated leg substantially within the single passageway. A method is provided for applying the furcation assembly to an optical cable. The apparatus and method of this invention apply to a variety of optical cable types.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to the field of fiber optic cable assemblies. More particularly, this invention relates to a high performance, flexible optical fiber furcation assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fiber optic communications has experienced explosive growth. In just a few years, the transmission of communication signals for voice, video, data, and the like has soared, and more growth is planned as fiber optic communication technology improves and networks expand to provide greater access.  
           [0003]    Inherent with any fiber optic network is the need to connect individual optical fibers from optical cables to other optical fibers by using one of a multitude of fiber optic assemblies. The connection of these optical fibers must be executed with great care and precision in order to minimize losses in the transmitted communication signal. These connections take a great deal of time because each optical fiber in a cable is usually manually routed and/or furcated and then individually connected to other optical fibers.  
           [0004]    When furcating optic cables, a furcation assembly is used to reduce microbending of the optical fibers, which is a bending of the optical fiber that causes signal attenuation. The furcation assemblies known in the art suffer from the shortcomings of being rigid, difficult to manufacture, difficult to install, and/or sensitive to environmental factors that damage the cable sheath and/or the optical fibers. This damage typically results in increased signal attenuation.  
           [0005]    A need therefore exists for a apparatus and method that provides an improved furcation assembly that enhances the performance of and minimizes the damage to optical fibers in a furcation assembly.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, the present invention is directed to an apparatus and method to protect furcated optical fibers against mechanical and/or environmental factors. The present invention is also directed to a high performance, flexible furcation assembly that minimizes bending in the optical fibers throughout the life of the furcation assembly. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the assembly and method particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0007]    To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the invention is directed to a furcation assembly that includes a flexible furcation body having a first end and an opposed second end with a single passageway extending therebetween, the first end for receiving a portion of a fiber optic cable and the second end for routing at least one furcated leg of the fiber optic cable out of the furcation assembly, and holding means for flexibly securing and for flexibly supporting the portion of the fiber optic cable and the at least one furcated leg substantially within the single passageway, such that the holding means minimizes bending of the portion of the fiber optic cable and the at least one furcated leg.  
           [0008]    According to another aspect, the invention is directed to a furcation assembly that includes a flexible furcation body having a single passageway with a first end and an opposed second end, the first end for receiving a portion of a fiber optic cable and the second end for routing a portion of at least one furcated leg of the fiber optic cable out of the furcation assembly, and holding means for flexibly securing and for flexibly supporting the portion of the fiber optic cable and the at least one furcated leg within the single passageway.  
           [0009]    According to yet another aspect, the invention is directed to a method of applying a furcation assembly to a fiber optic cable that includes inserting a portion of a first end of the fiber optic cable into a flexible furcation body, the flexible furcation body having a first end and an opposed second end with a single passageway therebetween, stripping a cable sheath from the portion of the first end of the fiber optic cable to expose at least one optical fiber, fanning out a portion of the at least one optical fiber, sliding the flexible furcation body over a predetermined portion of the fanned-out portion of the at least one optical fiber and over a predetermined portion of the first end of the fiber optic cable, and introducing a holding means into the furcation body, wherein the holding means flexibly secure and flexibly support the portion of the first end of the fiber optic cable and the fanned-out portion of at least one optical fiber substantially within the single passageway.  
           [0010]    According to another aspect, the invention is directed to a method of routing a fiber optic cable in a furcation assembly that includes inserting a portion of a first end of the fiber optic cable into a flexible furcation body, the flexible furcation body having a first end and an opposed second end with a single passageway therebetween, stripping a cable sheath from the portion of the first end of the fiber optic cable to expose at least one optical fiber, sliding the flexible furcation body over a predetermined portion of the at least one optical fiber and over a predetermined portion of the first end of the fiber optic cable, and introducing a holding means into the flexible furcation body, wherein the holding means flexibly secure and flexibly support the portion of the first end of the fiber optic cable and the at least one optical fiber substantially within the single passageway.  
           [0011]    It is to be understood that the both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.  
           [0012]    The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description serve to explain the principles of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a perspective view of fiber optic furcation assembly according to an embodiment of this invention;  
         [0014]    [0014]FIG. 2 is a partial cross-sectional view of the assembly of FIG. 1;  
         [0015]    [0015]FIG. 3 is an exploded perspective view of the assembly of FIG. 1; and  
         [0016]    [0016]FIG. 4 is a flowchart illustrating operations performed according to a method. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    This invention now will be described more fully hereinafter with reference to the accompanying drawings, in which several of the embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.  
         [0018]    Referring now to FIGS.  1 - 3 , a furcation assembly  10  in accordance with an embodiment of this invention is shown. The furcation assembly  10  includes a furcation body  12  having a single passageway  30  with a first end  14  and an opposed second end  16 , the first end  14  for receiving a fiber optic cable  18 , illustrated as an optical fiber ribbon, and the second end  16  for routing at least one leg  20  of the fiber optic cable out of the furcation assembly  10 . While and optical fiber ribbon is shown, any optical cable in any configuration could be used. As shown best in FIGS. 2 and 3, the optical fibers  19  from the optical cable  18  are separated into a number of legs  20  and, as described in more detail below, covered with fan-out buffer tubes  52  before exiting the furcation assembly. However, it should be noted that the optical fibers, depending upon the cable design being furcated, may not need to have the illustrated fan-out buffer tubes. If such buffer tubes are to be used, the buffer tubes  52  may be fabricated out of nylon and be dimensioned so that the optical fiber easily passes through the buffer tube. Preferably, the buffer tube  52  has an outer diameter of about 900 microns and an inner diameter sufficient to allow the optical fiber, which has an outer diameter of about 250 microns, to be inserted therein. As seen in FIG. 2, a first end of the buffer tube is disposed within the furcation body  12  and a second end of the buffer tube is disposed outside the furcation body  12 .  
         [0019]    The furcation assembly  10  also preferably includes a first fiber optic holding component  22  securable about the fiber optic cable  18 , and a second fiber optic holding component  24  securable around a portion of at least one leg of the fiber optic cable to support and secure the optical fibers during use and assembly, as discussed in more detail below. However, the holding components  22 , 24  may be excluded if desired as they assist in the manufacturing process, but are not required. The furcation assembly  10  also preferably includes a first furcation end component  26  securable about the first end  14  of the furcation body  12  and a second furcation end component  28  securable about the second end  16  of the furcation body  12 . While the first and second components (the fiber optic holding components and the furcation end components) are illustrated as being radially aligned with one another, they do not have to be and, in fact, may not be radially aligned depending on the size and length of furcation body  12 . Similarly, the holding components  22 , 24  and the end components  26 , 28  are preferably made of a glue-lined heat-shrink material, but any other material that would hold the optical fibers in place and seal the ends of the furcation body, respectively, would be acceptable, e.g., tape, bands, rubber boots, O-rings, etc. Furthermore, the end and holding components do not have to be of the same materials, but could be of any combination of acceptable materials. For example, the holding components could be rubber O-rings and the end components be rubber boots. Similarly, one holding component could be tape while the other end component is a glue-lined heat shrink material.  
         [0020]    The single passageway  30  is filled with a holding and adhesive material  50 , such as Dow Coming&#39;s® RTV sealant, filling the voids around the optical cable and that portion of the legs that are within the furcation body to thereby flexibly secure and support the fiber optic cable and optical fibers throughout the passageway  30 . The furcation end components  26 , 28  seal the holding adhesive material within the single passageway and provide further environmental protection for the optical cable and optical fibers within the furcation assembly  10 . The furcation body  12  is typically a flexible, lengthwise-extending, mesh tube having a hollow interior. Preferably, the furcation body is Varflex® HP tubing. The mesh tube, because it is breathable, allows the RTV sealant to cure around the cable, optical fibers, and legs. Other materials that cure and remain relatively flexible may also be used. However, the materials must cure without using heat, although UV-curable materials may also be used. If a UV-curable material is used, then the furcation body must be transparent to UV sources.  
         [0021]    In accordance another embodiment and as illustrated in FIG. 4, a method of applying a furcation assembly  10  to a fiber optic cable  18  is provided. The method includes, at step  101 , determining the location on the fiber optic cable where the furcation is to be located. At steps  103 - 107 , the cable is prepared for the furcation. At step  103  the cable can be inserted into a holding component  22 , preferably a glue-lined heat-shrink component, at the position where the optical fibers are to be separated from one another, and secured to the fiber optic cable. The holding component  22  keeps the optical fibers from separating from one another further down the cable and away from the furcation site than desired. As noted above, the holding component also assists in the process, especially if the fiber optic cable  18  contains a plurality of loose fibers. Then at step  105 , one end of the cable is prepared for the furcation. This step may include the striping of the ribbon matrix from the ribbon cable or other cable structure from the optical fibers, depending on the type of cable, to expose and separate or fan-out at least one optical fiber of about 250 microns in diameter, which will be the legs  20 . Obviously, any or all of the optical fibers in the optical fiber cable can be furcated in any given furcation assembly. At step  107 , a fan-out buffer tube  52  is preferably disposed over each optical fiber that is to be furcated. The fan-out buffer tubes  52  may all be bundled together with a second fiber optic holding member  24  before the optical fibers are placed therein. While this manner is preferable, the buffer tubes could be placed on each of the fibers before the buffer tubes are bundled together or they could be left loose. At step  109 , the second furcation end member  28  is positioned over one end of the optical cable and, at step  111 , a flexible furcation body  12  is positioned over cable so that the cable and fibers pass through the single passageway  30  of the furcation body  12 . If the end members can be wrapped around the cable, such as tape, then only the furcation body needs to be positioned over the cable before the end member. One end of the furcation body is disposed relative to the second furcation end member to allow the end of the furcation body to be sealingly engaged by the second furcation end component. The flexible furcation body  12  and furcation end component  28  are positioned over a predetermined portion of the fiber optic cable and the furcated legs  20 . As shown in FIG. 2, there is preferably a small gap between the first fiber optic holding member and/or cable (if no holding member is used or the cable extends beyond the holding member) and the end of the fan-out buffer tubes so that a portion of the optical fiber in each leg is exposed. At step  113 , the holding material is introduced into the furcation body and allowed to dry, cure, or set, depending on the holding material. The holding material preferably secures and supports the fiber optic cable, the portion of the exposed optical fibers, and the legs in a flexible manner within the single passageway. At step  115 , the first furcation end is disposed on the cable and securingly attached to the other end of the furcation body. It should be noted that either the first or the second furcation end member can be used first in the method and still be within the scope of the invention.  
         [0022]    Several common disadvantages in prior art furcation assemblies is that they are not flexible, have poor performance, and do not provide a mechanism to flexibly secure and support the fiber optic cable and optical fibers throughout the passageway to minimize the formation of microbends in the optical fiber(s). The furcation assembly of this invention is extremely flexible and is able to withstand a wide range of temperature cycling (e.g., −40° C. to 85° C.) while minimizing microbending, hold tensile loads up to three pound increments for up to two minutes, and endure many other rigors.  
         [0023]    Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.