MXPA96002131A - Grooved nucleus plug cable compa - Google Patents

Abstract

A slotted core type fiber optic slat cable includes a cylindrical rod having a plurality of helical slots on its outer surface. A groove retains a stack of fiber optic slats each having a flat arrangement of fiber optic in it. The pitch of the helical groove is selected so as to allow a total fiber optic threading effort of the edge fibers in the slat that is at least 0.05% and compression Ee in the middle fiber or middle fiber optics in the slat that is less of about 0.03%. The magnitude of the slot pitch is selected to be on the scale of Pc

Description

COMPACT GROOVED NUCLEUS SLOP CABLE BACKGROUND OF THE INVENTION The field of the invention is slotted core type fiber optic ribbon cables. Slotted core type fiber optic ribbon cables have been provided for use in subscriber circuits. Fiberglass slatted core cables of high fiber type should be designed to maintain the signal attenuation increase of the optical fibers in the cable within acceptable limits. Said attenuation can be caused by excessive bending of the optical fibers due to the forces exerted on the optical strips. Most grooved-core type fiber optic cables have either helical or helical grooves - which are reversed periodically. When a fiber optic strip containing a flat arrangement of optical fibers assumes an i * helical configuration during the threading after being placed in a slot having a helical configuration, various stresses are imposed on the optical fibers in the ribbon as a result of the helical configuration alone. The stress and thus imposed on the optical fibers in the durají batten the threading comprises contributions from the stress of elongation, bending stress and torque st. - The total fiber optic threading effort due to these contributions can be expressed as: Z ~ (e + € b.}.?? ~ £ £ + £ b) 2 + (2GVE) 2) -7-7 '(E uation where G is the modulus of elasticity in shear stress and E - is the Young's module of fiber optic, Tomita et al. Preliminary Research into Ultra High Density and High Count Optical Fiber Cables, 40th International Wire and Cable Symposium Proceedings pp. 8-15 (1991) Equation 1 does not include associated efforts with a tension (or compression) applied to a batten as an integer (for example, due to the counter-tension of the batten -w? f during the threading), nor does it include efforts introduced during the cable installation. The total fiber optic threading effort refers to the stress determined by Equation 1. The total fiber threading effort in a slotted core type fiber optic ribbon cable has been taught that it is limited to 0.05% or less.Therefore, a step of - 700mm helical groove has been selected in the design of cable dj. "In addition to fiber stresses during fabrication, 0.20% isntalation efforts should be allowed S. Hatano, Y 0 Katsuyama, T. Kokubun and K Hogari Multi -Hundred-Fiber cable of optical fiber ribons inserted tightly into slots, 35th International Wire and Cable Symposium Proceedings pp. 11 - 23 (1986) The helical pitch is sometimes referred to as the lon ging line 5 As illustrated in Figure 3, the radial distance R ^ between the center of the cable 0 and a end fiber in a -list is longer than the radial distance R between the center of the cable and the central optical fiber (s) in the ribbon, or more precisely, the midpoint of the expanded width by the optical fibers in the ribbon in the plane containing the optical fibers After the threading, this difference in length causes the edge optical fibers in a ribbon to be under tension, as recognized by the prior art. what The central optical fibers in the ribbon are under pressure. The width of the slat is a factor that affects the amount of compression, with the compression increasing with slat width. The lath width, in turn, is determined by the number of optical fibers in the lath and the thickness of the coatings on the individual optical fibers. The compression is also a function of the radial distance R between the strip and the center of the cable, whose distance must be at least the radial distance of the slot floor from the center of the cable. As the radial distance of the floor of the groove from the center of the cable increases, typically decreases-compression. The prior art has not fully taken into consideration the compression effect in the cable design optimization. Slotted-core type fiber optic latch cables containing lsitons each having a relatively small number of optical fibers have been proposed to have somewhat short slot passages and somewhat higher total stresses, for example, U.S. Pat. No. 4,826,279 proposed - a slotted core type fiber optic ribbon cable having five fiber slats with a slot pitch of 300 mm and a slot floor radius of 3.25 mm. However, slotted core type fiber optic ribbon cables that contain slats each having larger numbers of optical fibers have been taught to have longer slot passages. For example, Japanese patent publication 62-98313 proposed a fiber optic ribbon cable of grooved core type having ten fiber slats with a groove pitch of 550 mm and a groove floor radius of 3.25 mm, which it would result in a total fiber threading effort of less than 0.05%. The helical length of the optical strips in grooved core type fiber optic ribbon cable is a function of the groove pitch. In this way, all other factors being equal, a longer step helps reduce the cost of a cable by reducing the required fiber length. Although the factors listed above would tend to support the design of grooved-core type fiber-optic ribbon cables having a relatively long helical pitch, three other factors discussed below tend to support the design of such cables. They have a shorter step. First, during the bending of the cable, the sections of the lath on the outside of the fold are under tension and sections of laths inside the fold are under compression. The * Ribbons tend to move in the tension region to relieve - efforts. A shorter step advantageously accommodates said movement. Second, when a grooved core-type fiber optic ribbon cable is bent, the forces in the battens drive the slats to rotate to release the bend. A representation of such rotation is shown in Figure 4. The further the slats go, the deeper the slots must be to contain them, so that the outer diameter of the core spacer ribs must be larger. A larger cable is - the result. It has been found that a shorter slot pitch - reduces the amount of rotation of the liter. Therefore, all other factors being equal, a shorter slot pitch advantageously reduces the required cable size. Third, at low temperatures the plastic material in a grooved core type fiber optic ribbon cable tends to shrink. The laths typically shrink less than the rest of the cable, generating excess length of lath - and causing pressure to be exerted on the lanes. It requires extra space to accommodate this excessive lsiton length to avoid such pressures. It has been found that a shorter step reduces the additional space required to accommodate the extra slat length resulting from low-temperature conditions. Therefore, all other factors being equal, a shorter slot pitch again reduces the required cable size. * As the fiber count increases, the minimization of the diameter becomes more important. Fiber optic cables are typically smaller than comparable message capacity electrical cables. However, optical cables that have a high fiber count are typically larger than the fiber optic cables of lower fiber count already installed, and duct space is usually a major importance. Larger cables also typically have higher minimum dimen- sion diameters and may require larger and more specialized reels and threading equipment.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide high fiber bead-type fiber optic fiber ribbon cables which are smaller in outer diameter than comparable cables provided by the previous branch. Another object of the invention is to provide high fiber count slotted core fiber optic ribbon cables which can more reliably accommodate fiber stresses caused by the bending of the cable. Still another object of the invention is to provide fiber-optic ribbon cables of grooved core type of high fiber count which are less susceptible to pressures on the slats caused by shrinkage of materials at low temperatures. Still another object of the invention is to provide grooved core type fiber optic ribbon strips which are less susceptible to batten stacking rotation. Still another object of the invention is to provide fiber-optic ribbon cables of the high-flute-core grooved core type that are designed to limit the compression experienced by the average optical fibers on a batten during normal operating conditions. These and other objects are provided, in accordance with the present invention, by providing a grooved-fiber optic ribbon cable whose design is optimized by taking into account the compression in the medium optical fibers in the lath. The test has shown that the optical fiber attenuation rises unacceptably when said compression is more than 0.03%. While the outer diameter of the cable can be reduced by reducing the run length of the slots, the 0.03% limit compression is used to establish a lower limit on the slot length. The curve adjustment generates equations that resolve the step. These -equations, whose units are based on values of length -expressed in millimeters, are shown below. The invention is applicable to cables that have either true helical or helical grooves that are periodically reversed. A fiber-optic ribbon cable of the core type according to the invention comprises a cylindrical rod having a longitudinal axis and having on the outer surface thereof at least one groove having a helical pitch. At least one fiber optic strip is arranged in the slot. The slot may contain a plurality of fiber optic strips arranged in a stack. Each fiber optic batten has two main surfaces and cushions a flat arrangement substantially parallel to its main surfaces of at least eight optical fibers. Seen in cross section, the optical fibers, including any coatings thereon, expand to a width, thereby defining a midpoint of the width in the plane containing the optical fibers. A pod contains the fiber optic rod and strips. The cable typically contains a water blocking material, which may be a grease or gel-like material within the grooves, or a water-absorbing material such as a ribbon or yarn disposed within the grooves or between the outer jacket and the rod. The magnitude of the groove pitch is selected so that it is not less than the magnitude at which the compression e on the average otic fiber or optical fibers in the strip is 0.03%, and is also selected so that the force of Threading of total optical fiber on external optical fibers in the ribbon is greater than or equal to 0.05%. To fulfill the above conditions, the magnitude of * helical slot pitch is selected to be on the P ^ P ^ P scale, with P = (-6.718 + 76.094 W) + (-2.0.467 + csc 0.33014 W) Rr and Ps = (340.92 + 1.3495 Wf + 6.8775 Wr2) + (4.5417 - 0.07796 Wf - 0.037 Wf2) R4 > wherein P is the slot-passage, W is the width expanded by the optical fibers in the lath and R. is the radial distance between the longitudinal axis of the rod and the mid-point of the width expanded by the orthogonal fibers in the ribbon. The formulas in the presnete contemplate the use of values anifestados in terms of millimeters. A core-type fiber-optic ribbon cable terminated in an exemplary embodiment of the invention has a pitch in the scale of about 150 mm to about 350 mm and a width expanded by the optical fibers in the bottom of approximately 2 mm. millimeters This lath may contain eight coated optical fibers. * Another example of a grooved core type fiber optic ribbon cable made in accordance with the invention has a step in the scale of about 225 mm to about 400 mm and, the width expanded by the optical fibers in the approximately 3 mm ton. This Isiton can contain twelve coated optical fibers. Yet another example of a fiber-optic fiber ribbon cable made in accordance with the invention has a step on the scale of about 300 mm to approximate, * 4350 mm and a width expanded by the optical fibers in the ribbon of about 4 millimeters. This strip may contain sixteen coated optical fibers. Various methods have been found to allow the cable to operate acceptably despite having a total fiber optic threading effort exceeding 0.05. First, the grooved core type fiber optic ribbon cable according to one embodiment of the present invention may include optical fibers having a rating of 7.030 kilograms per square centimeter. slotted core type fiber optic lath according to one embodiment of the present invention may include fiber optic laths having a "-5 percentage of excess lath length equal to or greater than the value obtained by the subtraction of 0.05. % from the total threading effort of the optical fiber in said strip having the highest total threading effort Third, a fiber optic lath cable of the grooved 0-core type in accordance with one embodiment of the present invention. invention can have a cable effort rated in percentage during the installation of the cable which is eos of 0.20% - [= - 0.05%), where is the threading effort total maximum and splitting in the optical fibers during the manufacture of the cable. Brief Description of the Drawings Preferred embodiments of the invention are described in the various drawings, in which: Figure 1 is an isometric view of a cable according to the invention that has been cut for better understanding thereof; Figure 2 is a sectional view along the lines 2-2 of the cable of Figure 1; Figure 3 is a sectional view of a fiber optic batten in relation to the longitudinal axis of the cable; Figure 4 is a schematic view of rotation of the optical ribbon stacks during the flexing of a cable; and Figure 5 is a graph illustrating the preferred slit length scales for the cable based on the radius R of ribbon and fiber stress limits.

Detailed Description of the Invention The present invention will now be described more fully below. with reference to the accompanying drawings in which one or more preferred embodiments of the invention are shown. This invention, however, may be circumvented in many different forms and should not be considered as limited to the embodiments set forth herein; rather, these modalities are provided so that the disclosure fully transfers the scope of the invention to those experiments in the art.

The similar numbers are. They refer to elements similar to those in the exhibition. The drawings are not necessarily drawn to scale, but are configured to clearly illustrate the invention. A slotted core type fiber optic ribbon cable 10 according to the invention is shown in Figures 1 and 2. The cables in accordance with the illustrated embodiment can retain between 288 to 360 optical fibers. Of course, other embodiments may retain more optical fibers, such as a 600 fiber cable. The cable 10 includes a central resistance member 11 which is used as the tensile element of the ca. during installation. It serves as much as the cable tensile strength member as the compressive strength member of the cable. If the metal central strength member is desired, the resistance member 11 may be a rope made of braided steel wire flanges as shown in Figure 1. The wire may be composed of a central steel wire surrounding the wire.

! ^ F do by a trenszada layer of six steel wires in contact - with the central steel wire. In this example, the diameter of 0 strength member can be 4.8 mm, equal to three times the diameter of 1.6 mm of a single steel wire. In the alternative, the central resistance member 11 may be non-metallic. In such a case, a single composite rod - of tension fibers such as glass or aramid fibers embedded, 5 days in. Epoxy or plastic can be used.

Surrounding the central resistance member 11 is »A cylindrical rod 12 having a plurality of helical grooves 27 on its outer surface. In the preferred embodiment, the rod 12 is made of a plastic material that is extruded on the central resistance member 11. A so-called grooved core can be manufactured, comprising the central resistance member 11 surrounded by the rod 12, in a separate operation of a threading line. A method of manufacturing the grooved core with the use of a calibrating device? described in U.S. Patent No. 5,380,472 to Schneider, incorporated herein by reference. Each slot 27 on the outer surface of the rod 12 has a stack of fiber optic battens 13, each comprising a flat array of optical fibers as shown in Figure 3. Each fiber optic has a core 21 and a cover 22 surrounded by individual overlays 23 comprising a relatively soft primary coating and a relatively harder secondary coating applied directly on the primary coating. Surrounding the f_i. coated optical fibers is a common ribbon lath 34, which can be formed from a curable material - by ultraviolet light. Each individual optical fiber can have a different individual colored layer to distinguish it from other optical fibers in the ribbon. One of the ribs of the grooved rod extending between the grooves may be stripped to allow groove identification. In a preferred embodiment, each stack contains six lys. fiber optic tones 13 each containing a pious arrangement. of twelve coated optical fibers. Each slot 27 can have a width of 4.0 mm and a height of 4.1 mm. The distance of a groove floor 24 from the center of the cable is 3.55 mm and the so-called rod weft thickness 12 between the adjacent groove corners 25 of adjacent grooves is about 1.0 mm 5e. of 0.90 mm minimum weft when the rod is formed of medium density polyethylene material. In a preferred cable, water blocking gel is placed in the slots 27. A tape 14 comprising water absorption material directly surrounds the rod 12. On the tape 14 an inner tube 15 formed of plastic material such as polyethylene is extruded. . An optional covering layer 19 of metallic material lies on the inner tube 15, and an outer sheath 20 formed of plastic material, such as polyethylene, surrounds the layer ? ßr 19 covering. The cable 10 may also contain one or more break cords such as the break cords 17, 18 shown in Figure 2. The wire operates acceptably at temperatures of -40 C to + 70 Cs. The cable weights are 500 kg / km and have a diiie-s? only 22.5 mm. Its minimum bending radius is 36.01 cm - during installation and 27.0 cms. how it is installed In the cable as illustrated, the helical grooves 27 have a pitch of 250 mm. The helical slots 27 contain fiber optic ribbons each having a radius R | of 1 i s. Thickness of 3.7 mm for the fiber optic lsiton along the floor of the slot, each strip having a width of approximately 3 mm and containing twelve coated optical fibers. One way to limit the total stresses (including efforts during fabrication and during installation) on the optical shapes is to limit the installation effort, for example - by using a sufficiently large central member. Using the following formula, the total efforts can man. have less than 0.25%: Installation effort is less than or equal to 0.20% - (i - 0.05% in dorre is the total threading effort (Equation 2-) The cable shown has a maximum rated load rating during installation of 2700 N. Using a member 11 of sufficiently large central strength, the maximum installation effort is .0.11% and, £ is 0.10%. # satisfies /_~0.11% is less than or equal to 0.20% - (0.10% - 0.05%), or 0.15% _7 u the total effort is less than 0.25% _ / - 0.11% + 0.105% = 0.21%, which is less than 0.25% _7 In an alternative mode, the excess strip length allows the cable to undergo initial installation effort without the isntaling effort causing the optical fibers to experience additional stress. The length of Isitón - in excess of percentage of the fiber optic slats is made - that is greater than or equal to the percentage of effort experienced # by the optical fibers during the manufacture plus the percentage - of effort experienced by the optical fibers during installation minus 0.25%. The helical pitch of the slots 27 causes stress on the optical fibers in the slats. As illustrated in Figure 3, the radial distance Rf between the center of the cable 0 and an end optical fiber in a lath is more the distance than the radial distance R between the center of the cable and the central optical fibers in the ribbon. After threading, this causes the edge optical fibers in a ribbon to be under tension and the central optical fibers to be under compression. An example of how the desired slotted length is determined is as follows / Given a radius R of ribbon of 3.7 mm and optical fibers - each having an individual coating on it whose external diameter is 250 μm, Table 1 below exposes the? Rf radius of each individual optical fiber in the twelve fiber fiber optic strip adjacent to the floor of the slot. The optical fibers are numbered from left to right, with fibers 6 and 7 - the average optical fibers being on the ribbon. Due to the symmetry, the data for Fiber # 1 is equal to the data for Fiber # 12, the data for Fiber # 2 is equal to the data for Fiber # 11 and so on.

TABLE 1 Radio Rf of each optical fiber in the strip of twelve radio fibers R "of ribbon 3.7 mm, Fiber No. 1 or 12 2 ú 11 3 6 1 0 4 Ó 9 5 or 8 6 Ó 7 'f 3.9472 3.8673 3, 802 1 3. 7524 3. 71 90 3. 702 1 For each optical fiber i in Table I, HL., The ratio of optical fiber length i to the length of the rod axis for any given length of rod axis is given in Figure 2. This relationship can be express yourself as HL = / _ 1 + (2 R./P) _7, where R. is the distance from the center of the fiber i to the center of the rod and P is the groove pitch.

Table 2 Ratio of each optical fiber of helical length to length of rod axis and its average Fiber Number. ' Optics 200 1.00766 1.00735 1.00711 1.00693 1.00680 1.00674 1.00 250 1.00491 1.00471 1.00456? 1.00444 1.00436 1.00432 1.00 400 1.00192 1.00184 1.00178, 1.00174 1.00171 1.00169 1.00 The lengthening stress £ for each optical fiber is shown in Table 3. The values in Table 3 are obtained - using the data in Table 2 by subtracting the value of the average value of the individual fiber. The lengthening efforts * Negatives indicate compression.

Table 3 Percentage of Elongation Efforts * for each optical fiber Number of optical fiber Step 1 or 12 2 or 11 3 or 10 4 or 9 5 or 8 6 o (mm) 200 0.056 0.026 0.001 -0.017 -0.030 -0.0 250 0.036 0.016 0.001 -0.011 -0.019 -0.0 400 0.014 0.006 0.000 Ü0.004 -0.007 -0.0 Referring now to Figure 5, the data points in the four lower lines in Figure 5 were obtained permi- & for the average fibers of the strip it was -0.003 and then resolving for strip radius for a helical step of termination, called length of lay in Figure 5. The use of coated optical fibers having an outer diameter of 250 microns was assumed . The bottom set of points represents of is. Thus, the conditions at which the compression on the medium optical fibers is equal to 0.30%. The increased attenuation on the optical fibers was found to be within limits - acceptable when the 0.30% limit was not exceeded. The data points in the upper set of four lines in Figure 5 represent the conditions at which the total threading effort £ on the external optical fibers in the ribbon is 0.05%. Using the curve fitting, the following equation was generated for the bottom set of curves: P "= (-6.718 + 76.094 W) + (-2.0467 + 0.33014W) R. Again using the curve fitting, the following equation was generated for the upper set of curves: Psc = (40.92 + 1.3495 - 0.037 r2) Rr. The magnitude of the slot helical pitch, therefore, was selected to be on the Pc scale P < = - Psr with Pc = (- 6.718 + 76.094 W) + (-2.0467 + 0.33014 Wp) Rr and Ps = (340.92 + 1.3495 Wr + 6.8775 r2) + (4.5417 - 0.07796Rr - 0.037Wr2) Rr. wherein P is the helical groove pitch, W is the expanded width of the optical fibers in the lath and R is the distance -radial between the longitudinal axis of the rod and the midpoint of the width expanded by the optical fibers in the ribbon. It should be understood that the invention is not limited to the exact details of the construction, operation, exact materials or modalities shown and described, since modifications and equivalents will be apparent to one skilled in the art without departing from the scope of the invention.

Claims (10)

1. CLAIMS: c 1. A fiber optic ribbon cable of grooved core type, comprising: a cylindrical rod having a longitudinal axis and having on the outer surface thereof at least one groove having a helical pitch, the groove having a floor; a fiber optic batten having a main surface disposed adjacent to the groove floor in the at least one groove, each of said battens comprising a flat arrangement - of at least eight optical fibers that expand in cross-section to one width, defining in this way a midpoint of the width in the plane containing the optical fibers; and a cover containing the fiber optic rod and strips wherein the magnitude of the slot pitch is selected to be on the scale of P "- P -P", with cs P ,, = (-6.718 + 76.094 W ) + (-2.0467 + 0.33014 W) R. and * P = (340.92 + 1.3495 W ^ + 6.8775 W 2) + (4.5417 - 0.07796 W ^ - srrr 0.037 Wf2) Rr, where P is the slot pitch, W is the width expanded by - the optical fibers in the lane and R is the radial distance between the longitudinal axis of the rod and the midpoint of the width expanded by the optical fibers in the lower part of said isthon.
2. 2. A fiber optic ribbon cable of grooved core type as set forth in claim 1, wherein the * pitch of the helical grooves is in the range of about 150 mm to about 350 mm and, with the width expanded by the optical fibers in the lath is about 2 millimeters.
3. 3. A cable as set forth in claim 2, wherein the lath contains eight coated optical fibers.
4. 4. A grooved core type fiber optic ribbon cable as set forth in claim 1, wherein the pitch of the helical groove is in the range of about 225 to about 400 mm and the expanded width of The optical fibers in the ribbon is approximately 3 mm.
5. 5. A cable as set forth in claim 4, wherein the strip contains twelve coated optical fibers.
6. 6. A fiber optic isoton cable of the grooved core type as set forth in claim 1, wherein the pitch of the helical groove is in the range of about 300 mm to about 450 mm, and The expanded width of the optical fibers in the ribbon is around 4 millimeters.
7. 7. A cable as set forth in claim 6, wherein the strip contains ten and six coated optical fibers.
8. 8. A cable as set forth in claim 1, wherein each optical fiber has a voltage rating of at least 7,030 kilograms per square centimeter.
9. 9. A cable as set forth in claim 1, wherein the percentage of excess strip length is equal to or greater than the value obtained by subtracting 0.05% of the total threading effort of the optical fiber that has the total threading effort highest on that bar.
10. 10. A cable as set forth in claim 1, wherein the rated percentage of cable effort during the installation of the cable is less than 0.20% - (-0.05%), where e is the effort of threading maximum total imparted to the optical fibers during the manufacture of the cable. iw 11.- A cable as set forth in claim 1, wherein the percentage of excess strip length of the optical fiber strip is greater than or equal to the maximum percentage of threading stress experienced by the optical fibers during the manufacturing process. the percentage of effort experienced by - 5 optical fibers during installation minus 0.25%. 12. A fiber optic ribbon cable of grooved core type comprising: a cylindrical rod having a longitudinal axis and having on the outer surface thereof at least one slot having a helical pitch; at least one fiber optic strip arranged in the at least one slot, each strip comprising a flat arrangement of at least eight optical fibers; and a liner containing the rod and the optical fiber strips, wherein the magnitude of the slot passage is selected to be not less than the magnitude at which the compression,. In fiber optics or optical fibers with radial velocity, it is 0v3%, and is selected so that the total threading stress on the outer optical fibers in the ribbon is greater than or equal to 0.05%. 13. A grooved core type fiber optic ribbon cable as set forth in claim 12, wherein the pitch of the helical groove is in the range of about -150 mm to about 350 mm and, the width Expanded by the - optical fibers in the ribbon is approximately 2 millimeters. 14. A cable as set forth in claim 13, wherein the lath contains eight coated optical fibers. 15. A slotted fiber optic ribbon cable of the slotted nipple type as set forth in claim 12, wherein the pitch of the helical groove is in the range of about 225 mm to about 400 mm and, the width Expanded by the optical fibers in the ribbon is approximately 3 millimeters. 16. A cable as set forth in claim 15, wherein the lath contains twelve coated optical fibers. 17. A grooved core type fiber optic ribbon cable as set forth in claim 12, wherein the pitch of the helical groove is in the range of about 300 mm to about 450 mm and, the width expanded by The optical fibers on the ribbon is approximately 4 millimeters. 18. A cable as set forth in claim 17, wherein the lath contains sixteen coated optical fibers. * 19. A cable as set forth in claim 12, wherein each optical fiber has a voltage rating of at least 7,030 kilograms per square centimeter. 20. A cable as set forth in claim 12, wherein the percentage of excess strip length is equal to or greater than the value obtained by subtracting 0.05% of the total entanglement effort of the optical fiber that has the entangling effort. highest total in that bar. 21. A cable as set forth in claim 12, wherein the rated percentage of cable effort during - the installation of the cable is less than 0.20%. { - 0.05%), where £ is the maximum total threading stress imparted on the optical fibers during cable fabrication. 22. A cable as set forth in claim 12, wherein the percentage of excess length of fiber optic ribbon is greater than or equal to the maximum percentage of stress of * Threading experienced by the optical fibers during the fabrication plus the percentage of effort experienced by the optical fibers during installation minus 0.25%.