JP2005156712A - Optical fiber cable and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress fluctuation in transmission loss caused by temperature fluctuation of an optical cable, in which high-tensile bodies are arranged in a jacket member, branching after the middle is facilitated and fluctuations in the loss during work are suppressed. <P>SOLUTION: An optical fiber cable 1 consists of optical fiber units 7, in which one or a plurality of primary coated optical fibers 3 is coated by foamed resin 5, a jacket member 9 which covers a plurality of the optical fiber units 7 from outer circumference and a plurality of high-tensile bodies 11 which are buried in the jacket member 9 and arranged along a longitudinal direction. Inside of the jacket member 9 is divided by equal to or more than two or a plurality of optical fiber units 7. Many primary coated optical fibers 3 are divided into foamed resin 5 of the optical fiber units 7 and are arranged. Thus, generation of entanglement among the primary coated optical fibers 3 will not occur, and the fibers 3 are easily taken out. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber cable having a structure in which a tension member (strength member) is disposed not in the center of the cable but in a sheath portion of an outer layer, and a method for manufacturing the same, and in particular, transmission of an optical fiber housed in the cable. The present invention relates to an optical fiber cable that suppresses loss and a manufacturing method thereof.

  Conventionally, an optical fiber cable (hereinafter simply referred to as an “optical cable”) is generally provided at almost the center of the optical cable in order to prevent the optical fiber from being broken against a tensile force when the optical cable is extended and laid. A tension member (strength member) is arranged. As the tension member, a single metal wire such as a steel wire having a high Young's modulus or a stranded wire, or a non-metallic wire such as an FRP (Fiber Reinforced Plastics) wire or an aramid fiber is used.

  As an optical cable, an optical fiber strand (UV curable resin coating 250 μmφ), an optical fiber core wire (nylon coating 0.9 mmφ), or a multi-core optical fiber tape is twisted and assembled around the tension member. ing.

  However, in recent years, an optical cable has been proposed in which a tension member is not disposed at the center of the cable and is housed inside a sheath as a sheath member around the optical fiber, generally called a slotless structure.

  Referring to FIG. 4, an example of an aerial round type 24-fiber optical cable 101 is shown here. In this optical cable 101, six layers of four-core optical fiber ribbons 103 are laminated in the center of the optical cable 101, and PP yarn (polypropylene yarn) interposing members 105 are the six layers of four-core light. It is disposed around the fiber ribbon 103 and is extruded so as to be covered with a sheath 107 as a substantially cylindrical outer skin member. Further, at the time of extrusion molding, two tension members 109 and two tear strings 111 are vertically attached to the inside of the sheath 107 in the longitudinal direction of the optical cable 101.

  The two tension members 109 are arranged at positions facing each other across the cable center, and the two tear strings 111 are arranged in a direction substantially perpendicular to the opposing line of the two tension members 109 in the cable center. It is arrange | positioned in the position which opposes on both sides. Further, reinforcing ribs 113 are formed on the outer peripheral surface of the sheath 107 so as to be located outside the two tear strings 111.

  Referring to FIG. 5, the optical cable 115 of this example has a cable structure substantially similar to the optical cable 101 of FIG. 4, and a plurality of optical fiber strands 117 are replaced at the center of the cable in place of the optical fiber ribbon 103 of FIG. The other structure is the same as that shown in FIG. In the optical cable 115 of FIG. 5, the optical fiber element 117 and the interposition member 105 are vertically attached or twisted.

Also, the optical cable 101, 115 having a structure substantially similar to that shown in FIGS. 4 and 5 is provided with a suspension line, or hot melt resin is intermittently disposed instead of the central interposition member 105, and the water absorbing tape is formed. Thus, a center tube type optical cable such as a structure in which an inner core is formed (see, for example, Patent Document 1) or a tube structure in which the inner core is filled with jelly is exemplified.
JP 2000-241681 A

  By the way, in the structure of the conventional center tube type optical cable, when the optical fiber strand 117 (single-core wire) is used for the optical fiber to be applied like the optical cable 115 in FIG. there were.

  (1) In particular, when the number of optical fiber strands 117 is large, the optical fiber strands 117 are stored while being entangled with each other during cable manufacture, which causes an increase in loss. In the optical cable 115 of FIG. 5, when the optical fiber element 117 and the interposition member 105 are extruded so as to be accommodated in the sheath 107 by being vertically attached or twisted, the transmission loss temperature of the optical fiber element 117 after the cable is manufactured. There was a problem that the fluctuation became large.

  (2) When the optical fiber 115 is branched after the middle and an optional optical fiber strand 117 is taken out, the optical fiber strand 117 is entangled with the interposition member 105, so that the discriminability and separability from the interposition member 105 are poor. There is a high possibility of erroneous cutting, etc., and it becomes difficult to take out the optical fiber 117 at the time of intermediate post-branching, and the frequency of loss fluctuation is high during this work, and the fluctuation value also becomes large. It was.

  (3) For example, when removing the hot melt filling portion in the structure as in Patent Document 1 or the jelly of the tube structure, the frequency of loss fluctuation is high and the fluctuation value is also large.

  The present invention has been made to solve the above-described problems.

  The optical fiber cable according to the present invention includes a plurality of optical fiber units in which one or a plurality of optical fiber strands are covered with foamed resin, a skin member that covers each optical fiber unit from the outer periphery, and embedded in the skin member. It is characterized by comprising a plurality of strength members arranged vertically.

  In the optical fiber cable according to the present invention, in the optical fiber cable, it is preferable that the foamed resin and the outer member are made of the same material and integrated by heat fusion.

  In the optical fiber cable of the present invention, in the optical fiber cable, the center of the outer skin member is arranged in a direction substantially perpendicular to the direction in which the outer shell member is connected to a pair of strength members disposed at opposing positions sandwiching the center of the outer skin member. It is preferable that a pair of tear line bodies arranged at opposing positions sandwiched are vertically provided and incorporated.

  In the optical fiber cable according to the present invention, it is preferable that the plurality of optical fiber units are provided in the optical fiber cable so as to be identifiable.

The method of manufacturing an optical fiber cable according to the present invention includes a step of extrusion-coating one or a plurality of optical fiber strands with a foamed resin to form an optical fiber unit,
The plurality of optical fiber units, and a plurality of strength members disposed outside the optical fiber units, respectively, are driven and supplied to the extrusion head,
Extruding resin for the outer skin member to the extrusion head;
Extruding to coat the outer periphery of the plurality of optical fiber units with a skin member and vertically aligning the plurality of strength members so as to be embedded in the skin member;
It is characterized by comprising.

  In the optical fiber cable manufacturing method according to the present invention, in the optical fiber cable manufacturing method, it is preferable that the foamed resin and the outer member are made of the same material and integrated by heat fusion during extrusion molding.

  The optical fiber cable manufacturing method according to the present invention is substantially perpendicular to a direction in which a pair of strength members disposed at opposing positions sandwiching the center of the outer skin member are connected to the outer skin member in the optical fiber cable manufacturing method. It is preferable that a pair of tear filaments arranged at opposite positions sandwiching the center of the outer skin member in the direction are vertically attached and incorporated.

  The optical fiber cable manufacturing method according to the present invention is preferably such that each of the plurality of optical fiber units is identifiable in the optical fiber cable manufacturing method.

  As can be understood from the means for solving the problems as described above, according to the present invention, the optical fiber strand can be prevented from moving, and the optical fiber strand is coated with a soft foamed resin. Excellent impact resistance to wires.

  In addition, since the inside of the outer skin member is divided into a plurality of optical fiber units, the number of optical fiber strands in one optical fiber unit is limited and the remaining length ratio of the optical fiber strands is kept constant. Therefore, transmission loss can be suppressed.

  Further, the core wire of each optical fiber unit can be easily identified by coloring or marking the foamed resin itself of each optical fiber unit, which contributes to shortening of the connection work time.

  Further, since the optical fiber unit is soft and the foamed resin is soft, the optical fiber is not completely fixed, so that the loss temperature characteristic of the optical cable is excellent.

  In addition, since the outer member and the foamed resin are integrated by thermal fusion, the foamed resin can be cut together when the outer member is divided into two, so that the take-out property of the optical fiber is improved.

  Hereinafter, an optical fiber cable 1 according to an embodiment of the present invention (hereinafter, simply referred to as “optical cable” in the present embodiment) will be described with reference to the drawings.

  Referring to FIG. 1, an optical cable 1 according to this embodiment includes a plurality of optical fiber units 7 in which one or a plurality of optical fiber strands 3 are covered with a foamed resin 5, and the optical fiber units 7 are arranged from the outer periphery. For example, a sheath 9 as an outer skin member to be coated, a plurality of tension members 11 as longitudinal strength members arranged so as to be embedded in the sheath 9, and a plurality of members arranged vertically attached so as to be embedded in the sheath 9. For example, a tear string 13 is used as the tear line.

  More specifically, in this embodiment, in the optical fiber unit 7, eight optical fiber strands 3 are vertically attached and unidirectionally twisted or SZ twisted, and the periphery of the eight optical fiber strands 3 is foamed. Extrusion-coated with resin 5. The optical fiber 3 is configured by coating an outer periphery of a glass fiber having a diameter of 125 μm with an ultraviolet curable resin (UV resin) with a diameter of 250 μm. Further, as the foamed resin 5, a polyethylene resin is mainly used. At this time, the expansion ratio of the foamed resin 5 is suitably in the range of about 5 to 50 times.

  In this embodiment, the outer circumferences of the two optical fiber units 7 are covered with a sheath 9 by extrusion molding, and the sheath 9 is made of the same resin as the foamed resin 5, and the foamed resin 5 And the sheath 9 are integrated by heat fusion during extrusion. The outer diameter of the sheath 9, that is, the outer diameter of the optical cable 1 is 7 to 10 mm.

  In this embodiment, two tension members 11 are vertically attached to the sheath 9 so as to be embedded at opposing positions sandwiching the center of the cable. In FIG. 1, the two optical fiber units 7 are arranged in a direction orthogonal to the parallel direction.

  In addition, as said tension member 11, it is comprised using appropriate tensile-strength materials, such as a steel wire to 0.7-1.4 mmphi, glass fiber reinforced resin (FRP; Fiber Reinforced Plastics), an aramid fiber, a reinforced resin, for example. In this embodiment, a 0.7 mmφ single steel wire is used.

  In addition, the sheath 9 has, for example, a tear string 13 as two tear lines at a position facing the cable center in a direction substantially perpendicular to the direction connecting the two tension members 11. Arranged vertically. The two tear strings 13 are for tearing the sheath 9 to form two grooves on the sheath 9, and making it easy to tear the sheath 9 up and down with the two grooves as a boundary. .

  In addition, as said tear string 13, normally, tensile-strength polymer fibers, such as an aramid fiber and a polyethylene terephthalate fiber, metal wires, such as a steel wire, an aluminum wire, a lead wire, glass fiber, a cotton thread, etc. are used, and this embodiment Then, a 3000 d polyethylene terephthalate (PET) string is used.

  Further, a reinforcing rib 15 is formed on the outer peripheral surface of the sheath 9 so as to be positioned outside the two tear strings 13.

  Next, a method for manufacturing the optical cable 1 according to the embodiment of the present invention will be described.

  Referring to FIGS. 2A and 2B, when the optical cable 1 having the above structure is manufactured, an optical fiber unit 7 is manufactured in advance. As the optical fiber unit 7, FIG. As shown in Fig. 8, the eight optical fiber strands 3 are vertically attached from the eight optical fiber delivery bobbins 17 around which the optical fiber strands 3 are wound, and are unidirectionally twisted or SZ twisted and extruded. Is sent to an extrusion head 21 of a general extruder 19. When a plurality of optical fiber strands 3 are SZ-twisted, for example, eight optical fiber strands 3 pass through a core wire insertion hole arranged around the rotation center of a twist control plate (not shown). The twist control plates are twisted together by rotating in the forward and reverse directions. When the plurality of optical fiber strands 3 are twisted in one direction, the eight optical fiber delivery bobbins 17 are simultaneously twisted in one direction by rotating in one direction.

  In the extruder 19, for example, polyethylene resin as the foamed resin 5 is extruded and coated around the eight optical fiber wires 3 by the die 23 of the extrusion head 21, and the optical fiber unit 7 is extruded. The optical fiber unit 7 is cooled and wound on the optical fiber unit bobbin 25. In addition, the expansion ratio of the polyethylene resin is in the range of about 5 to 50 times.

  Next, in this embodiment, the two optical fiber units 7 delivered from the two optical fiber unit bobbins 25 are inserted into the dies 31 of the extrusion head 29 in the extruder 27 for extrusion molding.

  The die 31 of the extrusion head 29 has a shape that forms the sheath 9 into a substantially cylindrical shape, and the portion corresponding to the sheath 9 serves as two tension members 11 delivered from two tension member bobbins 33. A single steel wire having a diameter of 0.7 mm is inserted into the die 31 so as to be disposed at opposed positions sandwiching the center of the cable.

  Further, at the portion corresponding to the sheath 9 in the die 31 of the extrusion head 29, the polyethylene terephthalate tear string 13 made of 3000d as the two tear line bodies fed from the two tear string bobbins 35 is the above-mentioned. It is inserted into the die 31 so as to be disposed at a position facing the center of the cable in a direction substantially perpendicular to the direction connecting the two tension members 11.

  In addition, the extrusion head 29 is made of, for example, polyethylene resin made of the same material as the foamed resin 5 as the resin for the outer skin member as the sheath 9 so as to integrally go around the two tension members 11 and the two tear strings 13. It is configured to be extruded.

  In the above-described state, for example, a polyethylene resin as a resin material of the sheath 9 which is heated and molded is injected into the extruder and extruded from the extrusion head 29, so that the polyethylene resin of the sheath 9 becomes the two optical fiber units 7. It is extruded in a substantially cylindrical shape around it. That is, when the sheath 9 is pushed out, the extrusion is performed so that the two tension members 11 and the two tear strings 13 are integrated with the sheath 9. At this time, the two optical fiber units 7, the two tension members 11, and the two tear strings 13 are fed in accordance with the speed at which the polyethylene resin as the outer member resin is pushed out. The optical cable 1 having the cross-sectional shape shown in FIG. 1 is manufactured. At this time, since the sheath 9 and the foamed resin 5 are made of the same material, the sheath 9 and the foamed resin 5 are heat-sealed and integrated at the time of extrusion molding.

  That is, the manufacturing method of the optical cable 1 includes the following steps.

(1) Step of forming optical fiber unit 7 by extrusion coating eight optical fiber strands 3 with foamed resin 5 (2) Two optical fiber units 7 and the outside of the two optical fiber units 7 The two tension members 11 and the two tear strings 13 that are disposed on the belt are run and supplied to the die 31 of the extrusion head 29. (3) The resin 31 for the outer skin member is applied to the die 31 of the extrusion head 29. (4) The outer periphery of the two optical fiber units 7 is covered with a sheath 9 and the two tension members 11 and the two tear strings 13 are vertically attached so as to be embedded in the sheath 9. Extrusion molding process so that the two optical fiber units 7, the two tension members 11, and the two tear strings 13 are supplied, and the die of the extrusion head 29 The process of extruding the resin for the outer skin member from the cable 31 is simultaneously performed in a continuous process, and the optical cable 1 is quickly manufactured.

  The optical cable 1 configured as described above can prevent the optical fiber strand 3 from moving, and the optical fiber strand 3 is covered with a soft foamed resin so that the optical fiber strand 3 is impact resistant. Excellent characteristics.

  In addition, since the inside of the sheath 9 is divided into a plurality of optical fiber units 7, the number of the optical fiber strands 3 in one optical fiber unit 7 is limited, and the extra length of the optical fiber strand 3. This has the effect of keeping the rate constant.

  The remaining length ratio of the optical fiber 3 will be described. The length of the accommodated optical fiber 3 is, for example, 0.2 to 0.5% longer than the length of the optical cable 1. Therefore, if the variation in the extra length ratio between the optical fiber strands 3 increases, it causes an increase in loss. That is, in the conventional optical cable, when optical fiber strands are vertically attached and 20 or more optical fiber strands are coated with foamed resin to form a unit, the optical fiber strands in contact with the foamed resin The optical fiber strands that are not in contact with the optical fiber are likely to be generated, and the extra length of the optical fiber strands in the optical cable is varied. Therefore, the loss characteristics change due to the extra length difference.

  In addition, the optical fiber units 7 (groups) can be identified by coloring the foamed resin 5 itself of each optical fiber unit 7 or by applying alphanumeric characters or line markings on the surface of the foamed resin 5. Therefore, the core wire of the optical fiber 3 can be easily identified, and the connection work time can be shortened.

  Further, since the foamed resin 5 of the optical fiber unit 7 is soft, the optical fiber strand 3 is not completely fixed, so that the loss temperature characteristic of the optical cable 1 is also excellent.

  Further, in the cable branching property, since the sheath 9 as the outer skin member and the optical fiber unit 7 are integrated by heat fusion, the foamed resin 5 is cut together when the sheath 9 is divided into two. Therefore, the takeout property of the optical fiber 3 is facilitated.

  The optical cable 1 of the embodiment shown in FIG. 1 and the optical cable 37 as a comparative example shown in FIG. 3 were manufactured, and their characteristics were evaluated.

  In the optical cable 37 of the comparative example, basically, the inside of the sheath 9 is not divided into the plurality of optical fiber units 7 in the optical cable 1 of this embodiment, and the periphery of the 16 optical fiber strands 3 is single. The cable has a structure enriched with the foamed resin 39.

  That is, when the same member is described with the same reference numeral, 16 0.25 mmφ optical fiber strands 3 are vertically attached and extrusion-coated with a single foamed resin 39 polyethylene resin. Was coated with a polyethylene resin sheath 9 of the same material by extrusion molding to produce an optical cable 37 having an outer diameter of 7 to 10 mm. In addition, the arrangement structure of the tension member 11 as the two strength members and the tear string 13 as the tearing line body is the same as that of the optical cable 1 of this embodiment.

  In the optical cable 1 of the above embodiment and the optical cable 37 as a comparative example, the transmission characteristics and workability at the time of branching after the intermediate were verified.

  The cable 37 of the comparative example has a loss increase of up to 0.35 dB/km@1.55 μm in the loss measurement after the inspection of the finished product. When the OTDR (Optical Time Domain Reflectometer) waveform is confirmed, the increase in local loss is found. Admitted. In the loss temperature characteristic evaluation, a maximum loss increase of 0.42 dB/km@1.55 μm was observed at a loss of −30 ° C.

 On the other hand, the optical cable 1 of this embodiment showed good loss variation characteristics both when completed and during the temperature characteristic test.

  Further, an intermediate post-branching experiment of the optical cables 1 and 37 was performed. In this intermediate post-branching experiment, the work until the cable sheath 9 is peeled off and the inner optical fiber 3 is taken out is confirmed, and the workability is confirmed and the loss fluctuation (@ l.55 μm) during the work is sampled at a sampling period of 10 msec. Monitored.

The results are as shown in Table 1. In addition, (double-circle) is excellent, (circle) has shown that it is normal and (triangle | delta) is inferior.

  From Table 1, the cable of the comparative example was inferior in the visibility of the optical fiber 3 and the foamed resin 39 at the time of rear branching, and many occurrences of loss fluctuation were also observed at the time of rear branching. On the other hand, the optical cable 1 of this embodiment is excellent in the visibility of the optical fiber 3 at the time of rear branching, and loss fluctuation during operation does not occur.

  From the above results, the optical cable 1 of this embodiment has excellent transmission characteristics compared to the structure of the optical cable 37 of the comparative example, the optical fiber strands 3 are less likely to be entangled with each other, and the intermediate post-branching property is also good. I know that there is. As described above, in the comparative example, an increase in transmission loss of the optical fiber 3 was observed at −30 ° C. after the cable was manufactured. However, in the optical cable 1 of this embodiment, the temperature was lowered to −30 ° C. In FIG. 5, the transmission loss temperature fluctuation of the optical fiber 3 can be suppressed to a small level.

It is sectional drawing of the optical fiber cable of embodiment of this invention. (A) is schematic explanatory drawing of the manufacturing apparatus of an optical fiber unit, (B) is schematic explanatory drawing of the manufacturing apparatus of the optical fiber cable of embodiment of this invention. It is sectional drawing of the optical fiber cable of a comparative example. It is sectional drawing of the conventional optical fiber cable. It is sectional drawing of the conventional optical fiber cable.

Explanation of symbols

1 Optical cable (optical fiber cable; in this embodiment)
3 Optical fiber 5 Foamed resin 7 Optical fiber unit 9 Sheath (outer skin member)
11 Tension member (tensile body)
13 Tear string (tearing line)
15 Rib 17 Optical Fiber Delivery Bobbin 19 Extruder 21 Extrusion Head 23 Die 25 Optical Fiber Unit Bobbin 27 Extruder 29 Extrusion Head 31 Die 33 Tension Member Bobbin 35 Tear String Bobbin 37 Optical Cable (Comparative Example)
39 Foamed resin (comparative example)

Claims (8)

A plurality of optical fiber units in which one or a plurality of optical fiber strands are coated with foamed resin;
A skin member for covering each optical fiber unit from the outer periphery;
A plurality of tensile bodies arranged vertically to be embedded in the outer skin member;
An optical fiber cable characterized by comprising:   2. The optical fiber cable according to claim 1, wherein the foamed resin and the outer skin member are made of the same material and are integrated by heat fusion.   A pair of tear strips disposed at opposing positions sandwiching the center of the outer skin member in a direction substantially perpendicular to a direction connecting the pair of strength members disposed at the opposing positions sandwiching the outer skin member center with the outer skin member. The optical fiber cable according to claim 1 or 2, wherein the optical fiber cable is built in vertically.   4. The optical fiber cable according to claim 1, wherein the plurality of optical fiber units are provided so as to be identifiable. A step of extrusion-coating one or a plurality of optical fiber strands with a foamed resin to form an optical fiber unit;
A step of feeding each of the plurality of optical fiber units, and a plurality of strength members disposed outside the plurality of optical fiber units, respectively, to the extrusion head;
Extruding resin for the outer skin member to the extrusion head;
Extruding to coat the outer periphery of the plurality of optical fiber units with a skin member and vertically aligning the plurality of strength members so as to be embedded in the skin member;
An optical fiber cable manufacturing method comprising:   6. The method of manufacturing an optical fiber cable according to claim 5, wherein the foamed resin and the outer skin member are made of the same material and integrated by heat fusion at the time of extrusion molding.   A pair of tear strips disposed at opposing positions sandwiching the center of the outer skin member in a direction substantially perpendicular to a direction connecting the pair of strength members disposed at the opposing positions sandwiching the outer skin member center with the outer skin member. The method of manufacturing an optical fiber cable according to claim 5 or 6, wherein the optical fiber cable is built in vertically. 8. The method of manufacturing an optical fiber cable according to claim 5, wherein the plurality of optical fiber units are provided so as to be distinguishable from each other.

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