Abstract:
A flexible carrier for supporting and protecting elongated items such as optical fibers is disclosed. The carrier is formed from a substrate of interlaced filamentary members which may be woven, knitted or braided together. The elongated items are interlaced with or otherwise captured by the substrate during its manufacture. Various configurations of the substrate such as flat, pleated and tubular are feasible. Capture of the elongated members may be effected by integrally woven tubes formed within the substrate, by interweaving the items as warp yarns in a woven substrate or by laying in of the items in a knitted substrate.

Description:
RELATED APPLICATION  
         [0001]    This application is based on and claims the benefit of U.S. Provisional Application No. 60/316,371, filed Aug. 31, 2002.  
         FIELD OF THE INVENTION  
         [0002]    This invention relates to an article for supporting, organizing and protecting elongated items, particularly optical fibers.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is advantageous to provide relatively delicate, elongated items such as optical fibers with an external structure which supports, protects and organizes them. Support of the fibers prevents or mitigates mechanical stresses on the fibers which can cause degradation of fiber performance or even outright fiber failure. Stresses in the fibers which adversely affect transmission of optical signals may be caused by tensile or compressive forces, as well as by merely bending the fibers. Protection is necessary because the fibers are also generally subject to physical damage due to impact, shock and abrasion which can result from rough handling during installation, as well as conditions of service. Organization of the optical fibers permits ends to be readily identified and properly and quickly terminated regardless of the length or number of fibers being considered. Such organization is an invaluable time saver when the fibers are connected to other fibers or a device because it allows the ends to be connected to the appropriate mating fiber or terminal without the need for testing and identifying each fiber before the connection is completed.  
           [0004]    Currently, it is the practice to ensheath bundles of optical fibers within a tubular cable comprising a thin-walled outer jacket formed of flexible plastic such as PVC, PTFE, polyethylene or polypropylene. Alternatively, optical fibers are also protected in a flat ribbon of flexible plastic with the fibers arranged in spaced relation adjacent to one another across the width of the ribbon.  
           [0005]    The jackets, tubes and ribbons used with current optical fiber cables and ribbons tend to be relatively stiff as compared with the optical fibers and, thus, may impart significant forces on the optical fibers when the cable or ribbon is handled, twisted and bent during installation and servicing. Furthermore, optical fibers within a tubular cable are substantially disorganized and must be coded for identification to enable the ends to be properly terminated. Although the fibers remain organized and easily identifiable when flat ribbon is used to protect them, there are practical considerations limiting the width of the ribbon and thereby the number of optical fibers which can be supported with a particular ribbon. There is clearly a need for improvements in the support, protection and organization of optical fibers.  
         SUMMARY AND OBJECTS OF THE INVENTION  
         [0006]    The invention concerns a flexible carrier for supporting, protecting and organizing elongated items such as optical fibers. The carrier comprises a substrate formed of a plurality of interlaced filamentary members. The elongated items are captured within the substrate during interlacing of the filamentary members and are thereby fixed in position relatively to one another within the substrate.  
           [0007]    In a preferred embodiment, the elongated items are received within the substrate at a plurality of positions by being interlaced with the filamentary members. A group of the filamentary members is oriented transversely to and engageable with the elongated items at a plurality of crossing points positioned on opposite sides of the elongated items to fix the positions of the elongated items within the substrate. The filamentary members are preferably interlaced by weaving a first portion of them in a warp direction and a second portion of them in a fill direction. The elongated items are oriented substantially parallel to the first portion of filamentary members in the warp direction. The group engageable with the elongated items comprises a plurality of the filamentary members woven in the fill direction. These filamentary members are positioned in spaced relation to one another lengthwise along the substrate.  
           [0008]    In an alternate embodiment, the filamentary members are interlaced by weaving and are woven about the elongated items to form a plurality of elongated tubes positioned side-by-side and connected lengthwise, the tubes capturing the elongated items.  
           [0009]    It is an object of the invention to provide a device for supporting, organizing and protecting delicate elongated items.  
           [0010]    It is an object of the invention to provide a device which will support elongated items without subjecting the items to harmful stress.  
           [0011]    It is another object of the invention to provide a device in which the elongated items can be integrated during manufacture of the device.  
           [0012]    These as well as other objects and advantages of the invention will become apparent upon further consideration of the following drawings and detailed description of preferred embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a perspective view of a flexible, elongated carrier adapted to receive elongated filaments such as optical fibers;  
         [0014]    [0014]FIG. 2 is a perspective view of an alternate embodiment of the carrier shown in FIG. 1;  
         [0015]    [0015]FIG. 3 is a perspective view of a second alternate embodiment of the carrier shown in FIG. 1;  
         [0016]    [0016]FIG. 4 is a perspective view of another embodiment of a carrier according to the invention;  
         [0017]    [0017]FIG. 5 is a perspective view of a second alternate embodiment of the carrier shown in FIG. 1; and  
         [0018]    [0018]FIG. 6 is a plan view of a portion of a knitted substrate according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    [0019]FIG. 1 shows a carrier  10  according to the invention. Carrier  10  comprises a flexible, elongated substrate  12  comprising a plurality of filamentary members  14  interlaced together. Elongated items, for example, optical fibers  16 , are positionable lengthwise along the substrate  12  and are engaged and held thereto by filamentary members  18  which are oriented within the substrate substantially transversely to the optical fibers  16  and engage them at a plurality of crossing points  17  positioned on opposite sides of the elongated items. Preferably, the filamentary members  14  comprising the substrate  12  are interlaced by weaving and the transverse filamentary members  18  comprise fill yarns in the weave. Other filamentary members  14  are oriented lengthwise along the substrate to form warp yarns  20 . The optical fibers  16  are arranged substantially parallel to the warp yarns  20 . Although weaving is preferred, the filamentary members  14  may also be interlaced by braiding, as well as knitting.  
         [0020]    In the embodiment of the invention shown in FIG. 1, the optical fibers  16  are interwoven as warp yarns during manufacture of the substrate  12 . The warp and fill yarns  20  and  18  provide support and protection to the interwoven optical fibers  16 , the fill yarns  18  engaging the optical fibers by passing transversely over and under them and thereby retaining them to the substrate  12 . The optical fibers  16  do not need to be interwoven with every fill yarn  18 . Portions  19  of the optical fibers may be permitted to float along the surface of the substrate, and the fill yarns  18  which do engage the optical fibers  16  may be positioned in spaced relation along the length of the substrate  12 . The warp yarns  20 , being substantially parallel to the optical fibers  16 , keep them consistently positioned in spaced relation across the width of the substrate. The spacing is important because it preserves the relative position of the optical fibers to one another in the substrate, allowing them to be readily identified by their position without the need for separate coding. This methodical organization of the optical fibers allows them to be quickly and correctly connected to other optical fibers via mechanical connectors or to optical devices such as optical amplifiers and modulators, without the need for testing to identify each optical fiber.  
         [0021]    [0021]FIG. 2 illustrates an embodiment  22  of the carrier having a relatively wide substrate  24  which can be accordion folded with a plurality of reverse bends  26  forming pleats  27  extending lengthwise along the substrate substantially parallel to the warp direction indicated by arrow  28 . The inherent flexibility of the woven substrate  24  allows the pleats  27  to be formed easily without placing any significant stress on the interwoven optical fibers  16 , providing a relatively high density packing of optical fibers on a compact substrate. Since the substrate  24  is woven or knitted, the width may be varied over as wide a range as desired virtually without a practical limit.  
         [0022]    [0022]FIG. 3 shows another embodiment  30  of the carrier according to the invention, again comprising a substrate  32  preferably woven of fill yarns  18  and warp yarns  20 . Substrate  30  is woven into a plurality of tubes  34 , each tube having an interior space  36  adapted to receive one or more optical fibers  16 . The tubes are positioned side by side and connected lengthwise along a plurality of seams  38  defining and separating each of the tubes  34 . Seams  38  are preferably formed by well known interweaving techniques but could also be sewn, welded or bonded. Preferably, tubes  34  are woven around the optical fibers  16  as the substrate is manufactured thereby capturing the fibers securely within the tubes.  
         [0023]    The carrier according to the invention need not be substantially flat. As shown in FIG. 4, the carrier  40  comprises a substrate  42  which forms the sidewall  43  of an elongated sleeve  44 . Substrate  42  is preferably woven as a sleeve but could also be knitted or braided, or a flat substrate  12 , as shown in FIG. 1, could be formed into a circular shape around its long axis parallel to the warp direction  28  and opposite edges brought together and joined, for example, by sewing, bonding or welding. The carrier embodiment  40  has optical fibers  16  interwoven as warp yarns in the sidewall  43  of the sleeve  44  and also provides an interior space  46  which may be used to house other elongated items such as a wiring harness  48 .  
         [0024]    As shown in FIG. 5, sleeve  44  may also comprise tubes  34  arranged around a common center axis  35  oriented lengthwise along the sleeve, the tubes  34  each having an interior space  36  for receiving one or more optical fibers  16  or other elongated items. Similar to the flat substrate  32  shown in FIG. 3, the tubes are preferably integrally formed with the sleeve  44  and interlaced around the optical fibers  16  which during manufacture.  
         [0025]    [0025]FIG. 6 shows how elongated items such as optical fibers  16  may be integrally positioned within a knitted substrate  50 . Knitted substrate may be formed into a flat, pleated or sleeved configuration as described above for woven substrates. In the knitted substrate  50 , the filamentary members  52  are interlaced in a plurality of loops  54  forming a plurality of wales  56  arranged adjacent to one another in a plurality of courses  58 . The optical fibers  16  are laid into the substrate during knitting, transversely to the wales  56  and are engaged on opposite sides by the loops  54  which fix the optical fibers  16  in position within the substrate.  
         [0026]    The properties of the warp and fill yarns  20  and  18  play a role in determining the characteristics of the various substrate embodiments. Multifilament and monofilament polyester yarns are preferred for most applications since these yarns are readily available, easily woven, knitted or braided and have excellent tensile strength, flexibility and abrasion resistance. For a more flexible substrate, multifilament yarns are preferred. Monofilament yarns provide relatively better abrasion resistance than multifilament yarns but result in a less flexible substrate. Combinations of multifilament and monofilament yarns are feasible to realize both improved abrasion resistance and flexibility.  
         [0027]    Yarns of other materials, such as nylon and aramid fibers, may also comprise the substrate when special properties, such as high-temperature resistance or increased tensile strength are required.  
         [0028]    In addition to varying material properties of the yarns, the properties of the weave, knit or braid can also be adjusted to achieve desirable properties for the substrate. For example, the density of the weave may be set to a relatively high number of picks per inch to provide a substrate having a relatively closed mesh which securely fixes the position of the optical fibers. The mesh may also be relatively open allowing the optical fibers to float within the weave of the substrate.  
         [0029]    Furthermore, the pattern of the weave is another variable which may be used to achieve desired characteristics advantageous to the support and protection of the optical fibers. For example, the optical fibers may be engaged by fewer than all of the fill yarns in the weave, thereby reducing the number of contact points between the yarns and the fibers and providing relatively long runs of optical fibers which are not integrally woven in the substrate. Such a construction allows for the convenient branching of optical fibers at any desired point along the substrate.  
         [0030]    The carrier may be manufactured by interlacing a plurality of filamentary members to form a substrate and interlacing a plurality of the optical fibers or other elongated items with the filamentary members at a plurality of positions. During interlacing, the optical fibers are oriented transversely to a group of the filamentary members which engage the optical fibers at a plurality of crossing points positioned on opposite sides of the optical fibers thereby fixing the relative position of the optical fibers within said substrate. In a woven substrate, the fill yarns comprise the transverse filamentary members which form the crossing points with the optical fibers.  
         [0031]    Carriers comprising a plurality of filamentary members interlaced to form a substrate for the support and protection of elongated items such as optical fibers provide a durable, flexible, versatile and inexpensive means for conveying and organizing the items which is particularly suited to optical fiber applications.