JP2009086637A - Loose tube optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a completely dry loose tube optical fiber cable without using a jerry inside of a loose tube with reduced diameter while well maintaining the waterproof and temperature characteristics of the optical fiber cable. <P>SOLUTION: A loose tube optical fiber cable 1 includes: a centered tension member 3; a cable core 7 including a plurality of loose tubes 5 collected on the circumference of the centered tension member 3 wherein each of which loose tubes 5 houses at least one optical fiber; and a sheath 9 that covers the outer periphery of the cable core 7. The loose tubes 5 houses at least one water absorptive optical fiber 15 which has a single core optical fiber 23, and has a powdered absorbent 27 substantially uniformly applied and fixed on the outermost layer thereof by use of a water soluble UV resin 25 as a binder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a loose tube optical fiber cable, and more particularly to a loose tube optical fiber cable that minimizes water running in the longitudinal direction of the cable when the cable is submerged.

  European and American optical fiber cables have a loose tube type optical fiber cable structure in which optical fibers covered with a tube made of a thermoplastic material such as PBT are gathered around a central tension member and a sheath is provided. Yes. The tube structure generally has a structure in which jelly is filled as a waterstop material. However, since the jelly is sticky and the connection workability is not good, a structure in which the jelly is not filled for the purpose of improving the connection workability, that is, a tube structure having a dry space is attracting attention.

  As a water-stopping material in a dry tube instead of the above jelly, for example, a material obtained by applying a water-absorbing material to a yarn made of plastic such as polyester is already on the market.

  In addition, as an optical fiber and an optical fiber cable having a dry space with improved water blocking, for example, in Patent Document 1, a UV resin is coated as a primary coating layer on the outer periphery of a single-core bare optical fiber, and the primary The structure which coat | covered the water absorbing material of UV resin on the outer periphery of a coating layer is disclosed.

  Patent Document 2 discloses a loose tube type optical fiber cable in which yarns coated with a water absorbing agent are accommodated in each loose tube.

  Patent Document 3 discloses a loose tube type optical fiber cable in which talc is applied on an optical fiber bundle.

  Patent Document 4 discloses a loose tube type optical fiber cable in which calcium carbonate, talc, super water-absorbing polymer, etc. are housed in each loose tube.

Patent Document 5 discloses a loose tube type optical fiber cable in which a linear waterproof body is accommodated in each loose tube.
JP-A-3-137607 US7099542 US7203047 US6483971 gazette US5630003 Publication

  By the way, in recent years, the diameter and weight of optical fiber cables have been reduced for the purpose of improving the laying workability simultaneously with the drying of the loose tube. When a conventional water-absorbing material as shown in Patent Documents 1 to 5 is used without using jelly as a water stop material inside the loose tube, the diameter of the optical fiber cable is reduced for the following reason. Is difficult.

(1) Conventional existing water-absorbing material is generally a material in which a water-absorbing polymer is entangled with a fiber, and its linear expansion coefficient is different from that of an optical fiber such as an optical fiber core housed in a loose tube. Met. That is, since the shrinkage of the water absorbing material at a low temperature is larger than that of the optical fiber, the optical fiber in contact with the water absorbing material meanders due to the low temperature shrinkage of the water absorbing material and causes an increase in loss. In addition, when the inner diameter of the loose tube is reduced, the effect of low-temperature shrinkage of the water-absorbing material is increased, making it difficult to reduce the diameter of the loose tube.

(2) When the optical fiber core wire having the water absorption swellability of Patent Document 1 is used as the water stop material inside the loose tube, since the content of the water absorption material is limited, the clearance inside the loose tube is reduced. The upper limit is limited. Therefore, there has been a problem that it is difficult to design the inner dimensions of the loose tube that satisfies the waterproof performance while satisfying sufficient low-temperature characteristics.

  This invention is mainly a loose tube type optical fiber cable that realizes complete drying without using a jelly inside the loose tube and reduces the diameter while keeping the waterproof and temperature characteristics of the optical fiber cable good. Objective.

In order to solve the above-described problems, a loose tube type optical fiber cable according to the present invention is a cable in which a central tension member and a plurality of loose tubes each housing at least one optical fiber around the central tension member are assembled. In a loose tube type optical fiber cable composed of a core and a sheath coated on the outer periphery of the cable core,
It is characterized in that at least one water-absorbing optical fiber in which a water-soluble UV resin is used as a binder and a powdery water-absorbing agent is applied substantially uniformly and fixed to the outermost layer of the single-core optical fiber is housed in each loose tube. To do.

  Further, the loose tube type optical fiber cable of the present invention is the loose tube type optical fiber cable, wherein the single-core optical fiber of the water absorbing optical fiber is a linear expansion coefficient and strength of other optical fibers accommodated in the loose tube. It is preferably substantially the same as the mechanical properties such as Young's modulus.

  In the loose tube type optical fiber cable of the present invention, the loose tube type optical fiber cable has an inner diameter of about 1.4 mm and a temperature range of −45 ° C. to 80 ° C. A structure is preferred.

  In the loose tube type optical fiber cable of the present invention, the loose tube type optical fiber cable has a micro tube that has an inner diameter of about 1.3 mm and guarantees a temperature range of −30 ° C. to 80 ° C. It is preferable that it is a tube structure applicable to a duct cable.

  As will be understood from the means for solving the above problems, according to the present invention, the water-absorbing optical fiber is applied as the water-absorbing material in the loose tube, so that the waterproof property and temperature property of the optical fiber cable are good. The diameter can be reduced while keeping In addition, since the water absorption powder of the water absorption optical fiber is unlikely to drop off in a normal temperature and humidity environment, the inside of the loose tube and the optical fiber cable can be completely dried.

  In addition, since it is possible to realize a water-absorbing optical fiber having a diameter that is approximately the same as that of other optical fibers in the loose tube, the diameter of the loose tube and the optical fiber cable can be reduced.

  In addition, as a water-absorbing material in the loose tube, a water-absorbing optical fiber having mechanical properties such as linear expansion coefficient, strength, and Young's modulus equivalent to those of other optical fibers in the loose tube can be applied. Is easy to handle.

  In addition, by applying a water-absorbing optical fiber as the water-absorbing material in the loose tube, the water-absorbing optical fiber for indexing the position of the water-absorbing material at the time of flooding, or for communication between workers at the time of enforcement It can have added value as an optical fiber.

  Embodiments of the present invention will be described below with reference to the drawings.

  Referring to FIG. 1, a loose tube type optical fiber cable 1 (hereinafter simply referred to as “optical fiber cable”) according to this embodiment includes a central tension member 3 and a plurality of aggregates around the central tension member 3. The cable core 7 includes a loose tube 5 and a sheath 9 covering the outer periphery of the cable core 7. In this embodiment, six loose tubes 5 are stored, and two lip cords 11 are extended and stored in the longitudinal direction of the cable near the boundary between the inside of the sheath 9 and the cable core 7. .

Referring also to FIG. 2, the loose tube 5 includes at least one optical fiber 13 and at least one water-absorbing optical fiber 15 housed in a tube 17. In this embodiment, an inner diameter of _{d 1} is about 1.4mm in the tube 17 of thermoplastic material such as PBT or PP (jacket), within the tube 17, for example as a 12-core optical fiber 13 The optical fiber core wire 19 is accommodated, and talc 21 is uniformly applied to prevent adhesion between the tube 17 and the optical fiber core wire 19. The talc 21 is made of, for example, hydrous magnesium silicate (3MgO · 4SiO ₂ · H ₂ O).

  The optical fiber 13 may be an optical fiber strand, an optical fiber cord, or another form of optical fiber in addition to the optical fiber core wire 19 described above.

  Referring also to FIG. 3, the water-absorbing optical fiber 15 includes a single-core optical fiber 23, a water-soluble UV resin 25 provided substantially uniformly on the outer periphery of the single-core optical fiber 23, and the water-soluble UV resin. 25 is a binder and a powdery water-absorbing agent 27 fixed substantially uniformly on the outermost layer.

  In the present embodiment, the single-core optical fiber 23 is a single-core optical fiber 33 in which a secondary coating 31 such as polyamide resin is applied to the outer periphery of the optical fiber strand 29, and has a diameter of 250 μm in the longitudinal direction. It is uniform. The single optical fiber 23 may be an optical fiber, an optical fiber cord, or other forms of single optical fibers in addition to the optical fiber 33 described above.

  The water-soluble UV resin 25 is a UV resin for fixing a water-absorbing agent (binder). The outer diameter of the water-soluble UV resin 25 is 300 μm and is uniformly applied in the longitudinal direction. Moreover, as said water absorbing agent 27, the high water absorbing powder (a granular or powder water absorbing material) with a particle size of 10-50 micrometers is used, for example.

  Moreover, as a manufacturing method of said water absorption optical fiber 15, the water-soluble UV resin 25 before hardening is apply | coated substantially uniformly on the outer periphery of the single-core optical fiber 23. FIG. After the powdery water-absorbing agent 27 is applied almost uniformly on the outer periphery of the water-soluble UV resin 25, the water-soluble UV resin 25 is cured by irradiating the water-soluble UV resin 25 before curing with ultraviolet rays. The powdery water-absorbing agent 27 can be fixed to the outermost layer using a binder.

  Moreover, the waterproof performance of the above-mentioned tube 17 conforms to IEC 60794-1 (ice pouring on tap water end face, water head height of 1 m and no leakage after 24 hours). That is, the waterproof performance test of the loose tube 5 was conducted by using normal temperature tap water as a medium, setting the head height to 1 m (meter), the sample length of the loose tube 5 to 3 m (meter), and immersing for 24 hours. The waterproof property is evaluated.

  More specifically, in the waterproof test method, a water head tube was connected so that water pressure could be applied from one end side of the sample in a state where a 3 m sample was extended almost horizontally. The head tube is a cylindrical body that stands vertically from one end of the sample, and normal temperature tap water is poured into the head tube so that the head height is 1 m. The length of water running in a sample 24 hours after the tap water is added is measured.

  With the above configuration, in the loose tube 5, in the normal temperature and humidity environment, the water-absorbing optical fiber 15 functions as a binder by the water-soluble UV resin 25 fixing the water-absorbing powder 27 with a sufficient gripping force. The powder 27 is in a state in which it is difficult for the powder 27 to fall off the single-core optical fiber 23. That is, the inside of the loose tube 5 and the optical fiber cable 1 is completely dry.

  On the other hand, when the optical fiber cable 1 and the loose tube 5 are submerged, the water-soluble UV resin 25 of the water-absorbing optical fiber 15 of the loose tube 5 is dissolved in water, so that the water-absorbing powder 27 can be easily removed from the single-fiber optical fiber 33. Fall off. In addition, the dropped water-absorbing powder 27 swells and accumulates in the downstream direction of water immersion while maintaining an appropriate gel viscosity, so that the clearance in the tube 17 is sufficiently satisfied and the water is stopped. The waterproof performance is improved.

  In addition, the mechanical properties such as the linear expansion coefficient, strength, Young's modulus, etc. of the water-absorbing optical fiber 15 are substantially the same as those of the other optical fiber cores 19 accommodated in the loose tube 5, so that the environment changes. On the other hand, it is desirable in that it can be adapted in the same manner as the other optical fiber core wire 19 (optical fiber 13). That is, in the prior art, since the water-absorbing material has a lower temperature shrinkage than that of the optical fiber core wire 19 and meanders to cause an increase in loss, the diameter reduction cannot be realized. However, the water-absorbing optical fiber 15 of this embodiment is used. As a result, even if the environmental change occurs due to the above-mentioned reason, it does not meander and does not increase loss. As a result, it was possible to reduce the diameter of the loose tube 5. Furthermore, since the outer diameter of the water-absorbing optical fiber 15 is substantially the same as that of the optical fiber core wire 19, the loose tube 5 and the optical fiber cable 1 can be made thinner.

As described above, the loose tube type optical fiber cable 1 according to this embodiment is a 1-6 array type 72-core cable using one water-absorbing optical fiber 15 and six pieces of the loose tube 5 shown in FIG. . As described above, by using the water-absorbing optical fiber 15, in this embodiment, the inner diameter d ₁ of the loose tube 5 can be reduced to about 1.4 mm. the outer diameter _{D 1} of the fiber cable 1 could be less 9.0 mm.

  Further, even when the loose tube 5 and the optical fiber cable 1 are in a small diameter state as described above, the transmission loss of the optical fiber core wire 19 in the temperature range of −45 to 80 ° C. is shown in FIG. Thus, since it is between 0.18-0.25 dB / m, the fluctuation | variation part of transmission loss is 0.1 dB/m@1.55 micrometer or less, and is favorable. Therefore, it can be seen that the optical fiber cable 1 guarantees a temperature range of −45 to 80 ° C.

Further, the single-core optical fiber 23 of the water-absorbing optical fiber 15 in the loose tube 5 is a single-core optical fiber core 33, and the water-absorbing optical fiber 15 itself is not used as a medium for a normal optical communication line. It is used as a 2 ^nd Grade optical fiber (secondary optical test fiber). For example, it can be used as a short-distance meeting line during cable installation. That is, if one set (two sets) of optical talk sets is used, the workers at both ends of the loose tube 5 can be used as a meeting line for emergency communication.

  In addition, as shown in FIG. 5A, if the terminal of the water-absorbing optical fiber 15 is connected to the OTDR 37 installed in the monitoring room 35 in the telephone station after the cable laying construction, the inundation position can be easily determined. Can be done. At this time, the transmission loss of the water-absorbing optical fiber 15 is desirably 5.0 dB/km@1.55 μm or less, for example. As a result, when the water absorption powder 27 is dropped from the water absorption optical fiber 15 at the time of water immersion, as shown in FIG. By monitoring this transmission loss in combination with the OTDR 37, it is possible to detect a flooded location. Therefore, this water absorption optical fiber 15 can also be used as an infiltration detection fiber.

  From the above, the loose tube type optical fiber cable 1 of this embodiment has the following effects.

(1) By applying the water absorbing optical fiber 15 as the water absorbing material in the loose tube 5, the diameter can be reduced while keeping the waterproof property and temperature property of the optical fiber cable 1 good. Moreover, since the water absorption powder 27 of the water absorption optical fiber 15 is difficult to drop off in a normal temperature and humidity environment, the inside of the loose tube 5 and the optical fiber cable 1 can be completely dried.

(2) As the water absorbing material in the loose tube 5, the water absorbing optical fiber 15 having mechanical characteristics such as linear expansion coefficient, strength, Young's modulus, etc. equivalent to the other optical fiber core wires 19 housed in the loose tube 5 is applied. By doing so, the handling at the time of manufacture of the loose tube 5 is easy. In addition, since the water-absorbing optical fiber 15 with a diameter of about 300 μm, which is the same as the other optical fiber core wires 19, can be realized, the loose tube 5 and the optical fiber cable 1 can be reduced in diameter.

(3) By applying the water absorption optical fiber 15 as the water absorption material in the loose tube 5, the water detection optical fiber for indexing the position of the water absorption material at the time of water immersion, or for meeting between workers at the time of enforcement It is possible to have added value as a communication optical fiber.

  Next, a loose tube type optical fiber cable 39 according to another embodiment of the present invention will be described. In addition, since it is substantially the same as the optical fiber cable 1 of embodiment mentioned above, the same code | symbol is attached | subjected to the same member and detailed description is abbreviate | omitted.

Referring to FIG. 6, the optical fiber cable 39 is used as a micro direct cable specialized for pneumatic supply to a duct. Therefore, it is a 1-6 array type 72-core cable using one water-absorbing optical fiber 15 and six loose tubes 41 having the same structure as the loose tube 5 of FIG. As described above, by the water absorptive optical fiber 15 is used, the optical fiber cable 39 of this embodiment, it is possible to the inside diameter d ₂ of the loose tube 41 to achieve a reduced diameter of about 1.3 mm, which with the, the outer diameter _{D 2} of the optical fiber cable 39 could be 6.0 mm.

  Further, even when the loose tube 5 and the optical fiber cable 39 are in a small diameter state as described above, the transmission loss in the temperature range of −30 to 80 ° C. is 0.19 as shown in FIG. Since it is between ˜0.28 dB / km, the fluctuation of the transmission loss is 0.1 dB/km@1.55 μm or less, which is favorable. Therefore, it can be seen that the loose tube 41 guarantees a temperature range of −30 to 80 ° C.

  In addition, since the effect | action and effect of the optical fiber cable 39 are substantially the same as the case of the optical fiber cable 1 mentioned above, detailed description is abbreviate | omitted.

It is sectional drawing of the loose tube type optical fiber cable of embodiment of this invention. It is sectional drawing which shows the loose tube accommodated in the optical fiber cable of FIG. It is sectional drawing which shows the water absorption optical fiber accommodated in the loose tube of FIG. It is a graph of the transmission loss in the temperature range -45-80 degreeC of the optical fiber cable of FIG. (A) is schematic explanatory drawing in the case of determining the inundation position using the water absorption optical fiber accommodated in the loose tube of the optical fiber cable in FIG. 1, and (B) is a transmission loss at the inundation location on the OTDR screen. It is a schematic graph which shows a fluctuation | variation. It is sectional drawing of a micro direct cable with the loose tube type optical fiber cable of other embodiment of this invention. It is a graph of the transmission loss in the temperature range -30-80 degreeC of the optical fiber cable of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Loose tube type optical fiber cable 3 Center tension member 5 Loose tube 7 Cable core 9 Sheath 13 Optical fiber 15 Water absorption optical fiber 17 Tube 19 Optical fiber core wire 21 Talc 23 Single core optical fiber 25 Water-soluble UV resin 27 Water absorption powder (water absorption powder) Agent)
33 Optical fiber core 35 Monitoring room 37 OTDR
39 Loose tube type optical fiber cable (micro duct cable)
41 loose tube

Claims (4)

Loose tube type light comprising a central tension member, a cable core in which a plurality of loose tubes each containing at least one optical fiber are accommodated around the central tension member, and a sheath coated on the outer periphery of the cable core In fiber cable,
It is characterized in that at least one water-absorbing optical fiber in which a water-soluble UV resin is used as a binder and a powdery water-absorbing agent is applied substantially uniformly and fixed to the outermost layer of the single-core optical fiber is housed in each loose tube. Loose tube type optical fiber cable.   2. The single-fiber optical fiber of the water-absorbing optical fiber has substantially the same mechanical properties as other optical fibers accommodated in a loose tube, such as linear expansion coefficient, strength, Young's modulus, and the like. Loose tube type optical fiber cable.   The loose tube type optical fiber cable according to claim 1 or 2, wherein the loose tube has an inner diameter of about 1.4 mm and a tube structure that guarantees a temperature range of -45 ° C to 80 ° C.   3. The tube structure according to claim 1, wherein the loose tube has a tube structure applicable to a micro duct cable having an inner diameter of about 1.3 mm and a temperature range of −30 ° C. to 80 ° C. Loose tube type optical fiber cable.

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