JP2013174678A - Optical fiber cable and method of manufacturing optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cable which has excellent flexibility, and can suppress a loss due to bending of an optical fiber caused by shrinkage of a sheath under low temperature.SOLUTION: An optical fiber cable includes a plurality of optical fibers 11, an inner layer sheath 12 directly covering the peripheries of the plurality of optical fibers 11, a tension layer 13 composed of tension fiber covering the periphery of the inner layer sheath 12, and an outer layer sheath 14 covering the periphery of the tension layer 13 and applied with compressive strain in a cable longitudinal direction.

Description

  The present invention relates to an optical fiber cable and a method for manufacturing an optical fiber cable.

  As an optical fiber cable, a structure in which a tensile member (tension member) is built in the center and an optical fiber is twisted around the tensile member is known. Further, there is known a structure in which an optical fiber is arranged at the center and a tensile body is embedded in a sheath (outer jacket) covered with the optical fiber.

  In such an optical fiber cable, there is a problem that the flexibility of the cable is poor due to the high rigidity of the strength member. Further, if the structure has no strength member, there is a problem that when the environmental temperature is lowered, the optical fiber in the sheath is bent due to the contraction of the sheath, and transmission loss increases.

  In order to solve this problem, a method has been proposed in which an optical fiber is hardly bent due to its own rigidity and an increase in loss at a low temperature is suppressed (for example, see Patent Document 1). In order to avoid the influence of shrinkage of the sheath at low temperatures, it has been proposed to use a material having a negative linear expansion coefficient for the sheath (see, for example, Patent Document 2).

JP 11-31730 A Japanese Patent Laid-Open No. 62-118313

  However, in Patent Document 1, as the outermost sheath becomes thicker, the effect of shrinkage of the outermost sheath at low temperatures cannot be ignored, and there is a problem that the loss temperature characteristics at low temperatures deteriorate. Moreover, in patent document 2, the material which can be used for a sheath is restrict | limited, Furthermore, the problem that material cost is expensive remains.

  An object of the present invention is to provide an optical fiber cable and a method for manufacturing the optical fiber cable, which are excellent in flexibility and can suppress loss due to bending of the optical fiber due to shrinkage of the sheath at a low temperature. .

  According to one aspect of the present invention, a plurality of optical fibers, an inner layer sheath that directly covers the periphery of the plurality of optical fibers, a tensile layer that includes tensile strength fibers that cover the periphery of the inner layer sheath, and a periphery of the tensile layer And an outer layer sheath to which a compressive strain in the longitudinal direction of the cable is applied.

  According to another aspect of the present invention, forming a tensile layer composed of tensile strength fibers around an inner layer cable having a plurality of optical fibers and an inner layer sheath that directly covers the periphery of the plurality of optical fibers; Forming an outer sheath covering the periphery of the tensile layer, cooling the inner cable, the tensile layer and the outer sheath, pulling the inner cable, the tensile layer and the outer sheath at a first speed, and cooling. By running the outer layer sheath at a second speed higher than the first speed while the inner layer cable and the tensile layer are running at the first speed between the step and the taking step, the outer sheath is moved in the longitudinal direction of the cable. A method of manufacturing an optical fiber cable is provided.

  In another aspect of the present invention, the step of imparting compressive strain in the longitudinal direction of the cable to the outer layer sheath may cause the outer layer sheath to travel at the second speed using an intermediate character pillar.

  In another aspect of the invention, the second speed may be 1.1 to 1.5 times the first speed.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in flexibility and can provide the manufacturing method of the optical fiber cable which can suppress the loss by the bending of the optical fiber resulting from the shrinkage | contraction of the sheath at the time of low temperature, and an optical fiber cable. .

It is sectional drawing of a perpendicular direction with respect to the cable longitudinal direction which shows an example of the optical fiber cable which concerns on embodiment of this invention. It is sectional drawing along the cable longitudinal direction which shows an example of the optical fiber cable which concerns on embodiment of this invention. It is the schematic which shows an example of the manufacturing system of the optical fiber cable which concerns on embodiment of this invention. It is sectional drawing along the cable longitudinal direction of the optical fiber cable for demonstrating an example of the manufacturing method of the optical fiber cable which concerns on embodiment of this invention. It is a table | surface (the 1) showing the measurement result of the loss temperature characteristic of the optical fiber cable which concerns on the 1st Example of embodiment of this invention. It is a table | surface (the 2) showing the measurement result of the loss temperature characteristic of the optical fiber cable which concerns on the 1st Example of embodiment of this invention. It is sectional drawing of a perpendicular direction with respect to the cable longitudinal direction which shows an example of the optical fiber cable which concerns on the 2nd Example of embodiment of this invention. It is a table | surface (the 1) showing the measurement result of the loss temperature characteristic of the optical fiber cable which concerns on the 2nd Example of embodiment of this invention. It is a table | surface (the 2) showing the measurement result of the loss temperature characteristic of the optical fiber cable which concerns on the 2nd Example of embodiment of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(Structure of optical fiber cable)
As shown in FIG. 1, an optical fiber cable according to an embodiment of the present invention includes a plurality of optical fibers 11 and an inner layer sheath (first jacket) 12 that directly covers the periphery of the plurality of optical fibers 11. A tensile layer 13 made of tensile fibers covering the periphery of the inner layer sheath 12, and an outer layer sheath (second outer cover) 14 that covers the periphery of the tensile layer 13 and is provided with a compressive strain in the longitudinal direction of the cable. Is provided. An inner layer cable (optical fiber unit) 10 is constituted by a plurality of optical fibers 11 and an inner layer sheath 12.

  As the optical fiber 11, an optical fiber strand, an optical fiber core wire, an optical fiber tape core wire, etc. are employable. In the embodiment of the present invention, the number of the optical fibers 11 and the type of the optical fibers 11 are not particularly limited.

  As the tensile strength fibers constituting the tensile strength layer 13, aramid fibers such as poly-p-phenylene terephthalamide fibers such as Kevlar (registered trademark), glass fibers, carbon fibers, and the like can be used. The thickness of the tensile strength fiber is about 3000 to 50000 denier when an aramid fiber is used, about 20,000 to 300,000 denier when a glass fiber is used, and 20,000 to 300,000 when a carbon fiber is used. About denier.

  Each of the inner layer sheath 12 and the outer layer sheath 14 has a circular cross-sectional shape. The inner layer sheath 12 has a thickness of about 0.5 mm, and the outer layer sheath 14 has a thickness of about 0.3 mm to 1.2 mm. As a material for the inner layer sheath 12 and the outer layer sheath 14, polyethylene, polyvinyl chloride, nylon (registered trademark), or the like can be used.

  When the optical fiber cable according to the embodiment of the present invention is placed in a low temperature environment of about −10 ° C. or less, for example, the inner layer sheath 12 and the outer layer sheath 14 contract. At this time, with respect to the contraction of the inner layer sheath 12, since the inner layer sheath 12 is directly provided around the optical fiber 11, contraction in the longitudinal direction of the cable of the inner layer sheath 12 can be suppressed by the rigidity of the optical fiber 11, and the loss Increase can be suppressed.

  As for the contraction of the outer layer sheath 14, if the outer layer sheath 14 is not subjected to a compressive strain in the cable longitudinal direction, the difference in wire length between the contracted outer layer sheath 14 and the inner layer cable 10 becomes large. For this reason, as shown in FIG. 2, the inner layer cable 10 meanders in the outer layer sheath 14, the bending R occurs in the optical fiber 11, and the loss increases.

  On the other hand, according to the embodiment of the present invention, since the compressive strain in the cable longitudinal direction is preliminarily applied to the outer sheath 14 at the time of manufacturing the optical fiber cable, the cable longitudinal direction of the outer sheath 14 at a low temperature. The amount of contraction of the outer layer 14 and the inner layer cable 10 after contraction can be reduced. As a result, meandering of the inner layer cable 10 in the outer layer sheath 14 is suppressed, the bending R of the optical fiber 11 can be suppressed within a desired allowable bending, and an increase in loss can be suppressed.

  Furthermore, according to the optical fiber cable according to the embodiment of the present invention, since the tensile strength fiber is used as the tensile strength layer 13, the flexibility is superior to the case where a tension member made of a steel wire or the like is used.

  Note that the degree of allowable bending of the optical fiber 11 can be set as appropriate depending on the type and application of the optical fiber 11. Further, the contraction amount of the outer layer sheath 14 can be controlled by adjusting the amount of compressive strain applied to the outer layer sheath 14 so that the bending of the optical fiber 11 is within the allowable bending.

(Optical fiber cable manufacturing system)
The optical fiber cable according to the embodiment of the present invention can be manufactured by a manufacturing system as shown in FIG. 3, for example. An optical fiber cable manufacturing system according to an embodiment of the present invention includes a delivery device (bobbin) 1, an extruder 2, a cooling device 3, an intermediate caterpillar 4, a guide roller (guide pulley) 5, a take-up device 6, a guide roller ( A guide pulley 7, a tension control dancer 8, and a winding device (bobbin) 9.

  The delivery device 1 and the winding device 9 are each driven to rotate at a constant speed by a motor (not shown). As the cooling device 3, a water tank or the like can be used. The intermediate caterpillar 4 includes a plurality of pulleys 41a and 41b and a pair of flat belts 42a and 42b that are rotationally driven by the plurality of pulleys 41a and 41b, respectively. The take-up device 6 includes a take-up pulley 61 that is rotationally driven by a motor (not shown), and a belt wrap 62 that faces the take-up pulley 61.

(Optical fiber cable manufacturing method)
Next, an example of the manufacturing method of the optical fiber cable which concerns on embodiment of this invention is demonstrated. In addition, the manufacturing method of the optical fiber cable shown below is an example, and is not specifically limited to this.

  (A) Using an extruder (not shown), the inner layer sheath 12 is formed so as to directly cover the periphery of the plurality of optical fibers 11 as shown in FIG. The produced inner layer cable 10 is wound around the delivery device 1 as shown in FIG. Instead of winding the inner layer cable 10 around the delivery device 1, an extruder or the like (not shown) for producing the inner layer cable 10 is arranged in the previous stage of the extruder 2 to produce the inner layer cable 10 in-line. May be.

  (B) The delivery device 1 is rotationally driven to send out the inner layer cable 10 and run the inner layer cable 10 at the first speed. The first speed is, for example, about 4 m / min to 10 m / min, and is 6 m / min here.

  (C) The tensile strength fiber 13 is fed out using a feeding machine (not shown), and the tensile strength fibers 13 are gathered around the inner layer cable 10 using the inner layer cable 10 as a core and carried into the extruder 2. The outer periphery sheath 14 is formed by coating the periphery of the tensile strength layer 13 made of tensile strength fibers with a resin by extrusion using the extruder 2.

  (D) The outer layer sheath 14 is solidified by cooling the inner layer cable 10, the tensile strength layer 13 and the outer layer sheath 14 using the cooling device 3.

  (E) Between the cooling device 3 and the take-up device 6, the intermediate caterpillar 4 is used to accelerate the linear velocity of the outer sheath 14 as shown in FIG. 4, and at a second velocity V 2 that is faster than the first velocity V 1. Let it run. The second speed V2 is, for example, about 1.1 to 1.5 times faster than the first speed V1, for example, about 4.4 m / min to 15 m / min. On the other hand, the linear velocity of the inner layer cable 10 and the tensile strength layer 13 maintains the first velocity V1.

  (F) The take-up device 6 takes up the inner layer cable 10, the tensile strength layer 13, and the outer layer sheath 14 together at the first speed V1. Since the outer layer sheath 14 is fed from the intermediate caterpillar 4 at a second speed V2 that is higher than the first speed V1 of taking-up by the take-up device 6, compressive strain in the longitudinal direction of the cable is applied to the outer layer sheath 14. The magnitude of the compressive strain applied to the outer layer sheath 14 is appropriately set according to the type of the outer layer sheath 14 and the like, and can be controlled by adjusting the second speed V2. The extruder 2 pushes out the resin following the linear velocity of the outer layer sheath 14.

  (G) After being taken up by the take-up device 6, the optical fiber cable constituted by the inner layer cable 10, the tensile strength layer 13 and the outer layer sheath 14 to which compressive strain is applied is controlled in tension by the tension control dancer 8 and wound. It is wound up by the take-up device 9.

  According to the method for manufacturing an optical fiber cable according to the embodiment of the present invention, an optical fiber cable having excellent flexibility can be realized by forming the tensile layer 13 made of tensile fibers.

  Further, the outer sheath 14 is accelerated using the intermediate caterpillar 4 and is fed at a second speed V2 that is higher than the first speed V1 of the take-up device 6 to take a compressive strain in the longitudinal direction of the cable. Can be granted. As a result, it is possible to realize an optical fiber cable that can suppress a loss due to bending of the optical fiber 11 due to the shrinkage of the outer sheath 14 at a low temperature.

(First embodiment)
An optical fiber cable according to a first example of the embodiment of the present invention and a first comparative example will be described.

  First, as a first comparative example, an inner layer cable 10 was formed by directly applying an inner layer sheath 12 to 16 colored optical fiber core wires twisted in one direction as the optical fiber 11 shown in FIG. The thickness of the inner sheath 12 was set at two levels of 0.3 mm and 0.7 mm. The outer sheath 14 was formed by twisting six 1420 denier Kevlar (registered trademark) as the tensile strength layer 13 around the inner cable 10. The thickness of the outer layer sheath 14 was set to five levels of 0.3 mm, 0.5 mm, 0.7 mm, 1.0 mm, and 1.2 mm. As a first comparative example, an intermediate caterpillar 4 was not used, and an outer layer sheath 14 that did not impart compressive strain in the cable longitudinal direction was prototyped.

  On the other hand, as the first embodiment, the outer layer sheath 14 has a thickness of 0.7 mm, 1.0 mm, and 1.2 mm for each of two levels of the inner layer sheath 12 having a thickness of 0.3 mm and 0.7 mm. Prototype at the standard. Regarding the conditions where the thickness of the outer sheath 14 is 0.3 mm and 0.5 mm, the optical fiber cable according to the first comparative example has a good loss temperature characteristic, and thus was not prototyped (about the measurement result of the loss temperature characteristic). Will be described later.) As a first embodiment, the first speed V1 is 6 m / min, and the second speed V2 is 1.1 times (6.6 m / min) and 1.2 times (7.2 m) the first speed V1. / Min), and compressive strain in the cable longitudinal direction was applied to the outer sheath 14.

  About the optical fiber cable which concerns on a 1st comparative example and a 1st Example, the loss temperature characteristic of 3 cycles was measured at -10 degreeC and 55 degreeC. The holding time at each temperature was 6 hours or more, the cable length was 500 m, and the cable shape was a bundled state with a diameter of 300 mm.

  FIG. 5 and FIG. 6 show the measurement results separately when the thickness of the inner layer sheath 12 is 0.3 mm and 0.7 mm. The numerical values in FIGS. 5 and 6 indicate the amount of increase in loss (maximum value in 16 cores) at −10 ° C. in the third cycle with respect to the loss of the initial value at 1.55 μm. The case where the fluctuation amount of loss was less than 0.01 dB / km was described as “<0.01”, and the case where the fluctuation amount of loss was greater than 1.0 dB / km was described as “> 1.0”.

  5 and 6, in the optical fiber cable according to the first comparative example, the thickness of the outer sheath 14 is 0.3 mm in any case where the thickness of the inner sheath 12 is 0.3 mm and 0.7 mm. In the case of 0.5 mm, the fluctuation amount of loss is less than 0.01 dB / km, which is a good loss characteristic, but it can be seen that the loss increases as the outer layer sheath 14 becomes thicker.

  On the other hand, under the condition that the second speed V2 of the intermediate caterpillar 4 of the optical fiber cable according to the first example is 1.1 times, the loss is reduced as compared with the optical fiber cable according to the first comparative example, It can be seen that the loss is further reduced when the second speed V2 of the intermediate caterpillar 4 is 1.2 times.

(Second embodiment)
As an optical fiber cable according to the second example and the second comparative example of the embodiment of the present invention, as shown in FIG. 7, four intermittently fixed four-core tape cores 11a, 11b, 11c, and 11d are provided. Each of the cables was manufactured by twisting in one direction and covering with an inner layer sheath 12 to form an inner layer cable 10, around which a tensile strength layer 13 and an outer layer sheath 14 were formed. In FIG. 7, each group of intermittently fixed four-core ribbons 11a, 11b, 11c, and 11d is indicated by a one-dot chain line.

  By using the intermittently fixed four-core tape cores 11a, 11b, 11c, and 11d, the handling of the terminal portion becomes easier as compared with the integrated tape core. Further, unlike the integrated tape core wire, the bending direction is not restricted, so that it can be mounted in the cable at a high density. A prototype was manufactured under the same conditions as in the first comparative example and the first example except that the intermittently fixed four-core tape cores 11a, 11b, 11c, and 11d were used.

  For the optical fiber cables according to the second comparative example and the second example, the loss temperature characteristic was measured under the same conditions as in the first example. 8 and 9 show the measurement results. 8 and 9, in the optical fiber cable according to the second comparative example, the thickness of the outer sheath 14 is 0.3 mm in any case where the thickness of the inner sheath 12 is 0.3 mm and 0.7 mm. In the case of 0.5 mm, the fluctuation amount of loss is less than 0.01 dB / km, which is a good loss characteristic, but it can be seen that the loss increases as the outer layer sheath 14 becomes thicker.

  On the other hand, under the condition that the second speed V2 of the intermediate caterpillar 4 of the optical fiber cable according to the second embodiment is 1.1 times, the loss is reduced as compared with the optical fiber cable according to the second comparative example, It can be seen that the loss is further reduced when the second speed V2 of the intermediate caterpillar 4 is 1.2 times.

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1 ... Delivery device 2 ... Extruder 3 ... Cooling device 4 ... Intermediate caterpillar 5, 7 ... Guide roller (guide pulley)
6 ... take-up device 8 ... tension control dancer 9 ... take-up device 10 ... inner layer cable (optical fiber unit)
DESCRIPTION OF SYMBOLS 11 ... Optical fiber 11a, 11b, 11c, 11d ... Intermittent fixed 4 core tape core 12 ... Inner layer sheath 13 ... Tensile layer (tensile fiber)
14 ... Outer layer sheath 41a, 41b ... Pulley 42a, 42b ... Flat belt 61 ... Take-up pulley 62 ... Belt wrap

Claims (4)

A plurality of optical fibers;
An inner layer sheath that directly covers the periphery of the plurality of optical fibers;
A tensile layer comprising tensile fibers covering the periphery of the inner sheath;
An optical fiber cable comprising: an outer sheath covering the periphery of the tensile strength layer and provided with a compressive strain in the longitudinal direction of the cable. Forming a tensile layer composed of tensile strength fibers around an inner layer cable having a plurality of optical fibers and an inner layer sheath directly covering the periphery of the plurality of optical fibers;
Forming an outer sheath covering the periphery of the tensile layer;
Cooling the inner cable, the tensile layer and the outer sheath;
Withdrawing the inner cable, the tensile layer and the outer sheath at a first rate;
Between the step of cooling and the step of taking, the outer layer sheath is caused to travel at a second speed higher than the first speed while the inner layer cable and the tensile layer are caused to travel at the first speed. Thereby, applying a compressive strain in the longitudinal direction of the cable to the outer layer sheath.   3. The method of manufacturing an optical fiber cable according to claim 2, wherein the step of applying a compressive strain in a longitudinal direction of the cable to the outer layer sheath includes causing the outer layer sheath to travel at the second speed using an intermediate character pillar. .   The method of manufacturing an optical fiber cable according to claim 2 or 3, wherein the second speed is 1.1 to 1.5 times the first speed.

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