Abstract:
An optical fiber cable maintains an outer jacket, at least one optical fiber tube within the jacket and for each optical fiber tube, four optical fibers, arranged in a substantially squared arrangement. The optical fibers are linearly arranged along the length of the cable. The optical fibers are loosely arranged within the fiber tube in such a manner as to allow shifting of the straight optical fibers to conform to a bending of the cable, while being simultaneously constrained such that the straight arranged fibers do not become crossed-over or overlapped during bending.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 60/919,960, filed on Mar. 23, 2007, the entirety of which is incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of optical fiber cables. More particularly, the present invention relates to the field of optical fiber cables having an improved design and attenuation attributes. 
       BACKGROUND 
       [0003]    Optical fiber cables are well known in the communication industry as cables that include one or more optical fibers for optically transmitting communication signals. 
         [0004]    Among other constructions, one of the popular arrangements for optical fibers cables is a bundling of six to twelve individual optical fibers within a tube (also referred to as a buffer tube) in a loose arrangement, allowing for some movement of the optical fibers within the tube. This is referred to as a “loose tube” arrangement. Moreover, to form the optical fiber cable, one or more tubes may be bundled within an outer cable jacket for additional protection from the environment and also to provide an increased number of fibers within a particular cross section, useful for commercial installations. 
         [0005]    However, there are several competing concerns that affect the design and production of such optical fiber cables. The first of these concerns is the optimum amount of fibers per tube. In typical installations larger optical fiber cables have multiple tubes therein. The greater the number of fibers per tube, the greater the overall communication capacity for the optical fiber cable. However, more fibers per tube may result in difficulty accessing individual fibers within a tube (e.g. for connection to optical equipment). Furthermore, more fibers add weight to the cable as well as geometrical constraints, both of which add costs in the form of materials and production difficulties. 
         [0006]    A related second drawback to existing optical fiber cables of this design is the attenuation in fiber signals that occur when the optical fiber cable is bent. Attenuation occurs when individual fibers within an optical fiber cable are bent resulting in the optical signals being propagated therethrough to partially or totally exit the fiber. Increases in the number of fibers within each of the tubes in an optical fiber cable and their consequent geometric configuration, however restricts the possible movements of the fibers during bending, causing awkward and strained bending resulting in attenuation. 
         [0007]    Prior art FIG. 1 shows an exemplary prior art arrangement optical fiber cable having seven fiber tubes within a jacket. Prior art FIG. 2 shows a hypothetical bend of the fiber cable from FIG. 1. The centrally located tubes (b) can conform to the center of the bent cable, but tubes along axes (a) and (c) are either stretched or compressed, resulting in signal attenuation. Thus, the more fibers placed in fiber optic cable the more attenuation in the fiber signal, particular with fibers closer to the inside wall of the cable jacket. 
         [0008]    Given the constraints of attenuation from bending, combined with the desire to meet customer communication throughput needs by providing sufficient fibers per cable, prior art optical fiber cables are designed to include a substantial number of fibers per tube (typically between 6 and 12 fibers per tube). However, even with this range of fibers per tube, the attenuation at bend radiuses that occur in common installations results in significant signal attenuation. 
         [0009]    To address this, prior art designs have added to the cable either strength members or binding ribbons to resist bending (or to prevent over-bending as some bending is required) or they have added fillers such as petroleum jelly or other gels, in either the tubes or around the tubes in the jacket. U.S. Pat. No. 4,230,395 discusses an example of such gel filled tubes. Yet another method of preventing attenuation in the fibers in these cables is to strand the fibers in a helical or S-Z arrangement so that no one fiber is consistently disposed along the far side of a bend axis. 
         [0010]    All of these solutions are less than desirable. The addition of strength members adds additional construction components, adding cost in both materials and cable construction complexity. Furthermore, the strength members add additional weight to the final product. The addition of gel fillers also adds cost in both materials and extrusion complexity, adds weight, as well as the additional drawback of a fire fuel, which contributes to such gel filled cables failing the necessary fire safety standards for certain indoor uses. 
         [0011]    Stranding, adds significant cost to the production of a cable in that the twisting of the fibers requires that more fiber per foot of cable is necessary to span a given distance relative to a straight or non-stranded fiber cable. Also, in the stranded arrangement, fibers acquire an inherent wavy quality that includes a certain amount of bending, which can result in failure of the cladding to contain the light signal through reflection, resulting in undesired attenuation. 
       OBJECTS AND SUMMARY 
       [0012]    The present invention looks to overcome the drawbacks associated with the prior art and to provide an improved optical fiber cable that is both straight and that uses the least amount of additional bend protection components (to remove fire/fuel concerns). Such a fiber cable does not contain gel fillers or excessive strength members, while simultaneously provides a plurality of optical fibers per tube within the cable. The resulting structure is thus totally dry, relatively lightweight and maintains a fiber geometry within the fiber tubes that assists in preventing attenuation of optical signal. 
         [0013]    In one arrangement, an optical fiber cable maintains one or more tubes, each of which maintain four fibers per tube, which are snugly held in a longitudinal position. The arrangement is sufficiently tight to prevent random overlapping or criss-crossing that may lead to such faults as compression induced micro bending. The arrangement also simultaneously allows for the individual repositioning of the fibers from the neutral axis (in a bend) to obtain an optimum lowest-stress position. 
         [0014]    In one arrangement, the fibers are sufficiently loose within the tube so as to allow an installer the ability to perform a 20″ strip (strip capacity) without damaging the tubes/fibers within the jacket and the tube modulus is such that it allows repositioning of the fibers in the tubes, even under colder temperatures in the range of 0° C. through −60° C. 
         [0015]    In one arrangement, the four fiber tubes allow the fibers to be fed straight (un-stranded) during extrusion, with the possible addition of a water swellable yarn of sufficient flexibility that allows the fibers to continue repositioning themselves relative to a hypothetical neutral bend axis. 
         [0016]    To this end the present invention provides for an optical fiber cable having an outer jacket, at least one optical fiber tube within the jacket and, for each optical fiber tube, four optical fibers, arranged in a substantially squared arrangement. The optical fibers are linearly arranged along the length of said cable and the optical fibers are loosely arranged within the fiber tube in such a manner as to allow shifting of the straight optical fibers to conform to a bending of the cable, while being simultaneously constrained such that the straight arranged fibers do not become crossed-over or overlapped during bending. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  shows a prior art optical fiber cable; 
           [0018]      FIG. 2  shows a bent version of the prior art optical fiber cable from  FIG. 1 ; 
           [0019]      FIG. 3  illustrates an optical fiber cable in accordance with one embodiment; 
           [0020]      FIG. 4  illustrates an optical fiber cable in accordance with another embodiment; 
           [0021]      FIGS. 5A-5M  illustrate optical fiber cables of different sizes in accordance with several embodiments; 
           [0022]      FIG. 6  illustrates an optical fiber cable in accordance with one embodiment; 
           [0023]      FIG. 7A  illustrates the fiber tube cross section from the optical fiber cable from  FIG. 3  along a potential neutral axis; 
           [0024]      FIG. 7B  illustrates the fiber tube cross section from the optical fiber cable from  FIG. 6A  bent over the neutral axis; and 
           [0025]      FIG. 8  illustrates a sample 36 fiber cable with coloring of the fibers in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    In one embodiment,  FIG. 3  illustrates an optical fiber cable  10  according to the present invention. Optical fiber cable  10  includes an outer jacket  12 , a fiber tube  14 , and four optical fibers  16  contained within fiber tube  14  in a loose tube arrangement. 
         [0027]    Jacket  12  and tube  14  are preferably constructed of a standard polymer used in the optical fiber industry such as FRPVC (Flame Retardant Polyvinylchloride), PVDF (Polyvinydiene Fluoride), FEP (Fluorinated Ethylene Propylene) and PE (Polyethylene), however other polymers may be used based on desired fire safety, costs and flexibility considerations. Preferably, tubes  14  may be color coded for proper organization and identification of the tubes within cable  10  as will be described in more detail below. 
         [0028]    Fibers  16  are preferably typical UV coated optical fibers  250  microns in diameter of the type commonly used in fiber optic signal transmission. As with tubes  14 , preferably fibers  16  may be color coded for proper organization and identification of the fibers within cable  10 . 
         [0029]    In another embodiment, illustrated in  FIG. 4 , water swellable yarns  18  may be added to the center of tube  14  between fibers  12 . Water swellable yarns  18  are optionally helically spun and are used for both moisture absorption and to create a buffer space in the center of fibers  16  so that after extrusion and assembly of tubes  14 , there is room in the center of fibers  16  for movement during the bending of cable  10  as explained in more detail below. 
         [0030]    In one embodiment,  FIGS. 5A-5G  show various arrangements for cables  10  having one or more tubes  14 , each of which maintain a four fibers  16  per tube configuration as described above.  FIGS. 5H-5M  show additional arrangements of larger cables  10  having more numerous tubes  14  and a central component  20  such as strength member formed, by example, from GRP (Glass Reinforced Polymer). 
         [0031]    It is understood that the above described cables  10  are exemplary configurations. Any similar cables  10  using one or more tubes  14 , each of which having similar four fiber geometry, are within the contemplation of the present invention. 
         [0032]    In the above described cables  10 , in each case, tubes  14  still maintain the above geometry of four fibers  16 . Turning now to the size and geometry of tubes  14 , preferably the outer diameter of tube  14  is substantially 0.042″ and the inner diameter is substantially 0.025″. Such an arrangement allows 20″ strip capability for the installers of cable  10  while maintaining optical signal capacity at or above attenuation performance standards such as GR-409, GR 20 and ICEA 596 in temperatures in the range of 0° C. through −60° C. (with a possible attenuation change of 0.10 db/km at the lower rated temperatures). In an alternative arrangement which may perform in the lower range (of −40° C. through −60° C.), the outer diameter of tube  14  is substantially 0.038″ and the inner diameter is substantially 0.0245″. Here the strip capacity is reduced to 1″-3″ due to the coefficient of friction or tightness of the jacket  14  against fibers  16 . 
         [0033]    Using the above example of an outer diameter of 0.042″ as a basis, and based on the fiber  16  diameters of 250 nm or 0.00984″, a 5% gap is created between the internal diameter of tube  14  and fibers  16 . For example, as shown in  FIG. 6 , calculating the diameter of a circle drawn hypothetically around the four fibers  16  (labeled “H” in  FIG. 6 ) is done according to the following equation: 
         [0000]      (1.41421+1)×0.00984″=0.023761.[(√2+1)×Diameter of fiber] 
         [0034]    As this diameter is substantially 5% less than the internal diameter of tubes  14 , there is room for fibers  16  to flex their center&#39;s position relative to a neutral axis of bending (but not randomly twists or cross each other) within tube  14  during bending as described below. 
         [0035]    In another embodiment, a gap of about 4% is feasible in the arrangement with the outside/inside diameter of jacket  12  as 0.038/0.0245. 
         [0036]    Such an inner diameters for tube  14  are ideal for using a 0.25″ setting on the commonly used miller stripping tool, and where the gap between the fibers  16  and tube  14  and the ability of fibers  16  to move somewhat, prevents them from being cut during stripping. 
         [0037]    It is understood that although the above examples show an inner diameter of tube  14  as 0.025″ it is possible that a larger diameter may be used up to 0.02622″ (four fibers  16  diameter+¼ fiber diameter) and even up to 0.02868″ (four fibers  16  diameter+¾ fiber diameter). The limit of such internal diameter of tube  14  being that it provides a sufficient gap to allow fibers  16  to move within tube  14  given the low modulus of the plastic used for tube  14 , while simultaneously being allowed sufficiently little space so as to prevent random twisting or tangling of the un-stranded fibers  16 . 
         [0038]    Furthermore, the above arrangement, with the above described internal diameters of tube  14 , is also dimensioned to allow a 20″ strip of tube  14  from fibers  16 . This is facilitated by the substantially 5% gap between fibers  16  and tube  14  and is such that the design couples the stiffness necessary to prevent the fibers from becoming wavy within tube  14  while not being overly constricted against fibers  16 . 
         [0039]    In another arrangement, the wall thickness is reduced from 0.00875″ (OD−ID/2 or 0.042−0.0245/2) to 0.0085″, and possibly as low as 0.004″ whereby this reduced amount of plastic for tubes  14  would lend less restrictive forces to fibers  16  by way of less volume or mass. In such an arrangement the inner diameter of tube  14  may be placed in the range of substantially 0.027″ and an outer diameter of 0.035″. 
         [0040]    In the present example, the polymer employed for tubes  14  of this reduced-wall thickness construction may employ a Young&#39;s modulus that results in a lower tensile strength range of 2500 PSI-2800 PSI with a coefficient of thermal expansion of substantially 3×10 5 -5×10 5  per 0° C. as opposed to polymers used in typical prior art arrangements using 4000-10,000 PSI rated polymers. One example of polymer used for tubes  14  may be a 2800 PSI tensile FRPVC plenum grade polymer. 
         [0041]    The dimensions of optical fibers  16  and tubes  14  described above is such that cables  10  are able to be constructed with a minimum or no strength members as well as without the need for stranding of fibers  16 . As described below, the four-fiber geometry allows for optimum movement during bending, without crowding of the fibers so as to optimize between bending stress durability and the number of high multi-fiber cables  10 . 
         [0042]      FIG. 7A  illustrates cable  10  along a potential bend axis. In this configuration, each fiber  16  is separated from the hypothetical neutral bend axis by ½ of its diameter. Thus, according to a hypothetical 3 inch bend radius, the fiber circumference delta (length/length) is calculated as: 
         [0000]      (0.005″/3″)×100%−0.17% 
         [0043]    Because fibers  16  are not locked into tubes  14  some mis-matching in length may occur when cable  10  is bent. When a cable/tube is bent around any radius the fibers closest to the inner circumference of the bend exhibit a mismatch in total distance needed to be traversed versus those fibers along the outer circumference of the bend. The resulting differences in distance causes a fiber length mis-match which is one of the contributing factors to undesirable attenuation. 
         [0044]    For example, Table 1 below, is a comparison of fiber length mismatch assuming a coil of 3″ radius (bend radius)  10  where the concern would be about the relative length mismatches between each of the fibers  16  as they follow the various circumferences as shown in the following table 1. 
         [0045]    Columns 1 and 5 are for four fibers in a locked (stranded, wrapped, no gap etc . . . ) arrangement, columns 2 and 6 are for four fibers according to the present arrangement, columns 3 and 7 are for six fibers in a tube according to the prior art and columns 4 and 8 are for  12  fibers in a tube according to the prior art 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 
                           
                 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Central Axis radius (inches) 
                 3 
                 3 
                 3 
                 3 
                 6 
                 6 
                 6 
                 6 
               
               
                 Number of fibers 
                 4 
                 4 
                 6 
                 12 
                 4 
                 4 
                 6 
                 12 
               
               
                 Approximate fiber diameter (inches) 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
               
               
                 Fiber Group Diameter (inches) 
                 0.017 
                 0.017 
                 0.024 
                 0.035 
                 0.017 
                 0.017 
                 0.024 
                 0.035 
               
               
                 Closet Fiber Distance from axis (inches) 
                 0 
                 1 
                 0 
                 1 
                 0 
                 1 
                 0 
                 1 
               
               
                 Farthest fiber distance from axis (inches) 
                 0.012 
                 0.005 
                 0.014 
                 0.025 
                 0.012 
                 0.005 
                 0.014 
                 0.025 
               
               
                 Closest fiber circumference (inches) 
                 9.42 
                 9.42 
                 9.42 
                 9.42 
                 18.85 
                 18.85 
                 18.85 
                 18.85 
               
               
                 Farthest fiber circumference (inches) 
                 9.46 
                 9.44 
                 9.47 
                 9.50 
                 18.89 
                 18.87 
                 18.90 
                 18.93 
               
               
                 Circumference mismatch (%) 
                 0.40% 
                 0.17% 
                 0.48% 
                 0.82% 
                 0.20% 
                 0.08% 
                 0.24% 
                 0.41% 
               
               
                   
               
               
                             indicates data missing or illegible when filed 
               
             
          
         
       
     
         [0046]    In another example, Table 2 shows a similar chart to Table 1 regarding fiber length mismatches only with a more extreme bending situation of 20 turns on a 7″ mandrel. 
         [0047]    For example, if cable  10  or tube  14  of fibers  16 , in an extreme situation, is wrapped around a 0.7″ diameter mandral for 20 turns, this would further exacerbate the the cumulative mismatch of lengths between each of fibers  16  within tube  14 , generating a significant strain. This strain occurs during the bending of the cable where the outer fibers  16  along the out circumference of the bend are stretched and the inner fibers  14  along the inner circumference of the bend buckle, as they are forced (through friction etc . . . ) to eqiuvicate, at least partially, their length with the shrinking length of the inner diameter of tube  14  and the lengthening of the outer diameter of the tube  14  during the winding. 
         [0048]    Column 1 is for four fibers in a locked arrangement, column 2 is for four fibers according to the present arrangement, column 3 is for six fibers in a tube according to the prior art and column 4 is for 12 fibers in a tube according to the prior art. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
             
             
               
                 Mandrel Wrap 
                   
                   
                   
                   
               
               
                 # turns 
                 20 
                 20 
                 20 
                 20 
               
               
                 Mandrel (inches) 
                 0.7 
                 0.7 
                 0.7 
                 07 
               
               
                 unit od (inches) 
                 0.044 
                 0.044 
                 0.05 
                 0.053 
               
               
                 length (inches) 
                 46.75 
                 46.75 
                 47.12 
                 47.31 
               
               
                   
                   
                 Shifted 
               
               
                 Central Axis radius (inches) 
                 0.7 
                 0.7 
                 0.7 
                 0.7 
               
               
                 Number of fibers 
                 4 
                 4 
                 6 
                 12 
               
               
                 Approximate fiber diameter 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
               
               
                 (inches) 
               
               
                 Fiber Group Diameter (inches) 
                 0.017 
                 0.017 
                 0.024 
                 0.035 
               
               
                 Closet Fiber Distance from 
                 0 
                 1 
                 0 
                 1 
               
               
                 axis (inches) 
               
               
                 Farthest fiber distance from 
                 0.012 
                 0.005 
                 0.014 
                 0.025 
               
               
                 axis (inches) 
               
               
                 Closest fiber circumference 
                 2.20 
                 2.20 
                 2.20 
                 2.20 
               
               
                 (inches) 
               
               
                 Farthest fiber circumference 
                 2.24 
                 2.21 
                 2.24 
                 2.28 
               
               
                 (inches) 
               
               
                 Circumference mismatch (%) 
                 1.72% 
                 0.71% 
                 2.07% 
                 3.52% 
               
               
                 Cumulative mismatch (inches) 
                 0.8061 
                 0.333906 
                 0.976 
                 1.665 
               
               
                   
               
             
          
         
       
     
         [0049]    From the above two tables, column 2, representing the four-fiber  16  arrangement of the present invention results in the lowest cumulative mismatch percentages, regardless of the number of turns. Such an advantage becomes more pronounced over the six fiber and twelve fiber prior art designs as the number of turns is increased (such as in table 2). 
         [0050]    For example, the 0.17% fiber mismatch of the present four-fiber arrangement is a significant improvement over the 0.48% mismatch and 0.82% mismatch of the six and twelve fiber prior art arrangements respectively. 
         [0051]    As shown in  FIG. 7B , the four fiber geometry of tubes  14  results in a bend configuration whereby two of fibers  16  (shown as upper and lower fibers  16  in  FIG. 6B ) remain apart from the bend axis and two of fibers  16  (shown as left and right fibers  16  in  FIG. 6B ) within tube  14  move into the bend axis. Such an arrangement, allows half of the fibers to remain in the bend axis, a configuration that higher count fiber tubes from the prior art can not achieve, and thus results in the potential circumference mismatch of the present invention being shifted from 0.40% as in the prior art to 0.17%, as noted in Table 1. 
         [0052]    Stated another way, in this case the minimum stress state (0% mismatch) is reached for the two fibers  16  that occupy the neutral axis of the potential bend. 
         [0053]    In other embodiments of the present invention, such bend results are similarly achieved in each of the tubes  14  in the case of multi-tube  14  cables  10  such as those shown in  FIGS. 5B-5M . For example, in these arrangements, tubes  14 , constructed as above, are then stranded as a larger population of tubes  14  within a larger jacket  12 , possibly around a csm (central strength member  20 ). 
         [0054]    In one example of cable  10  having several stranded tubes  14 , the lay length (stranding rate) of tubes  14  is preferably set to be substantially equal to the smallest typical drum diameter on which they are wrapped onto. For example, a cable  10  having several tubes  14  of the above construction stranded within a single jacket  12 , may be stranded at a 12″ lay length assuming that cable  10  is to be wound on a typical drum having a diameter of 12″ 
         [0055]    This stranded arrangement for tubes  14  within jacket  12  allows tubes  14  within cable  10  to achieve bends of a radius as low as 3″ (or smaller in non-continuous bends), with the looseness of tubes  14  within jacket  12  allowing for sufficient adjustment to the bend stress. 
         [0056]    Shorter lay lengths may be used when csm  20  is employed. In any case, the stranding of tubes  14  within cable  10  is such that the longitudinally arranged four fiber tubes  14  is such that necessary stiffness is retained in tubes  14  to prevent repositioning or cross over of the non-stranded fibers  16  therein during the bending of cable  10  as discussed above. 
         [0057]    It is noted that there are some commercially available twelve fiber/per tube, multi tube cable structures where the fibers are S-Z stranded and encased within a gel filled tight tube. In these prior art arrangements the inside diameter of the tubes are 0.045″ or 25%-32% greater than the twelve fiber group outside diameter or 0.034″-0.036″. This spacing of 0.045″-0.035″, or a 0.010 thickness, results in a fiber-inner tube diameter gap of a full fiber width which sometimes allows a crossover of fibers. These assemblies are thus highly compression or crush sensitive. To prevent attenuation, the units are very loosely stranded within hard double walled exterior assembly to prevent compression&#39;s direct impact with the interior of the fibers/tubes. In some cases this necessitates a cable outside diameter of 0.429″ for a 72-fiber cable as compared to an outside diameter of 0.274″ for a 72-fiber cable. Also the utilization of gel in this prior art arrangement as mentioned before in the background is a fuel and prevents such a design from being used in plenum spaces or having a plenum rating. 
         [0058]    As a result of the dimensions noted above, and the resulting beneficial geometry of the four fiber tube  14 , a 40-70% cost reduction in materials is achieved over the traditional cable configurations having the same fiber counts/per cable. Furthermore, the present design achieves attenuation results in the range of approximately 0.4/0.3 dB/km at 1310 nm-1550 nm for single mode fibers; 02.23/0.56 dB/km at 850 nm-1300 nm for 50 micron fibers; and 2.85/0.57 db/km at 850 nm-1300 nm for 62.5 micron fibers at room temperature after manufacture. This indicates a very small increase in attenuation in the range of 0.05-0.1 dB/km from the incoming fiber, prior to placement within the tight tube. Prior art cables having the same number of fibers  16  arranged in tubes with more than four fibers per tube, such as six and twelve fiber dry tubes, which display attenuation results in the range of 1.4/1.3 dB/km for single mode fibers resulting in a typical 1 db increase in attenuation. Similarly, multimode fibers of 50 micron or 62.5 micron core diameter typically see an increase in 0.5-1.0 db/km in the 6 and 12 fiber dry tight tubes at their measured and operation wavelengths of 850 and 1300 nm. With gel, presumably the attenuation of these six and twelve fiber tubes could be reduced somewhat, but it would then be unable to meet the desired fire safety standards. 
         [0059]    In sum, the above described four fiber  16  construction within tubes  14 , regardless of whether cable  10  maintains one or more tubes  14 , allows the opportunity to achieve a minimal stress state on fibers  16  without stranding the fibers within tubes  14  or having a great area of looseness within tube  14 . The longitudinal orientation of fibers  16  greatly aids in crush performance as fibers  16  are not criss-crossing when weight is applied to cable  10 . This prevents fibers  16  in the present arrangement from mircobending on themselves as is the case with the prior art arrangements where attenuation results from crisscrossing of stranded fibers within the tubes and the allowance of random fiber placement in the larger looser tubes. 
         [0060]    In another embodiment, it is understood that the four fiber  16  per tube  14  arrangement as described herein is different than the typical six and twelve fiber industry standard arrangements. In order to facilitate back-connection to pre-existing color coding systems, such as the TIA 598 color standard, the arrangement of the present invention is such that for every three tubes  14 , all twelve color fibers  16  of the standard colors are represented. 
         [0061]    For example, the current TIA standard employs a twenty four color standard which calls for twelve colors different colors, then using the same twelve colors with black dashes for fibers thirteen through twenty four. 
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Color Code Chart: Fiber Optic Cables* 
               
             
          
           
               
                 Fiber/Tube No. 
                 Color 
               
               
                   
               
             
          
           
               
                 1 
                 Blue 
               
               
                 2 
                 Orange 
               
               
                 3 
                 Green 
               
               
                 4 
                 Brown 
               
               
                 5 
                 Gray 
               
               
                 6 
                 White 
               
               
                 7 
                 Red 
               
               
                 8 
                 Black 
               
               
                 9 
                 Yellow 
               
               
                 10 
                 Purple 
               
               
                 11 
                 Rose 
               
               
                 12 
                 Aqua 
               
               
                   
               
               
                 *Per TIA/EIA 598-A 
               
             
          
         
       
     
         [0062]    For example, as illustrated in  FIG. 8 , in one arrangement of a forty eight fiber cable  10  having twelve tubes  14 , each of four fibers  16 , the tubes  14  may be colored in accordance with the below described sequence. The first four tubes colored Brown, Blue, Red and Violet each maintain four fibers  16  of the colors Blue, Orange, Green, and Violet. The second four tubes  14  are colored Orange, Slate, Black and Rose and each maintain four fibers  16  of the colors Slate, White, Red and Black. Finally, the third set of four tubes  14  are colored Green, White, Yellow and Aqua and each maintain four fibers  16  of the colors Yellow Violet Rose and Aqua. 
         [0063]    In such an arrangement, for each set of three tubes  14  (as shown sequentially divided in Figure), the arrangement of the present invention has the twelve color fibers  16  from the conventional arrangement for group connectorization or ribboning with existing 
         [0064]    While only certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes or equivalents will now occur to those skilled in the art. It is therefore, to be understood that this application is intended to cover all such modifications and changes that fall within the true spirit of the invention.