JP2013142853A - Optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-core optical fiber cable with a thin diameter and high density which is not in danger of giving excess tension or side thrust to an optical fiber core, and is excellent in core wire discriminability.SOLUTION: A cable core is formed by holding a first tensile strength body 3 capable of suppressing tension to be applied to an optical fiber core 1 in construction to a fixed level or less at an approximate center part of a cross section of a cable over the entire length of the cable by a tensile strength holding part 51, and arranging a plurality of optical fiber core wires formed by twisting together or being straightly assembled among a plurality of partition wall parts 52 which extend from the tensile strength holding part 51 in the radial direction toward a cable jacket 2 in the cross section of the cable and divide the inside of the cable jacket 2 in the cross section of the cable over the entire length of the cable. The cable jacket 2 in which a second tensile strength body 4 capable of suppressing extraction and contraction of the cable jacket 2 to be generated due to temperature variation is arranged in the longitudinal direction of the cable is applied to the outer peripheral of the cable core.

Description

  The present invention relates to an optical fiber cable used for optical communication.

  Currently, optical fiber cables are widely used as communication media in optical communications. There are various types of optical fiber cables depending on the application. For example, in an area close to a telecommunications carrier building, it is necessary to lay many optical fibers for wiring to users. A cable is used (for example, see Patent Document 1).

  Optical fiber cables are installed on underground pipes and pipes in buildings, etc. in addition to being interfered with by power poles. However, with the rapid increase in demand for optical communication in recent years, multiple optical fiber cables are installed on one pipe or pipe. The method of laying optical fiber cables is used.

  However, if the outer diameter of an optical fiber cable (existing optical fiber cable) already installed in the pipeline is large, additional optical fiber cables cannot be installed due to a lack of free space inside the pipeline or piping. There is. Therefore, an optical fiber cable having a smaller diameter and higher density structure is required. Recently, an optical fiber cable having a structure in which a plurality of optical fibers are assembled at a high density as described in Patent Document 2 has been proposed for the purpose of reducing the diameter and density of the optical fiber cable.

  Now, for example, the work for laying an optical fiber cable in an underground pipeline is as follows. (1) A rope for pulling the optical fiber cable (hereinafter referred to as a pulling rope) is inserted from one work point A of the pipe line to be laid with the optical fiber cable, and the other work point B of the pipe line is inserted. Leave until. (2) At the work point B, fix the tip of the optical fiber cable installed at the tip of the tow rope. (3) At the work point A, the optical fiber cable is pulled to the work point A by pulling the tow rope, and is laid in the pipeline.

  In such a laying operation, a large tension is applied to the optical fiber cable. When this tension is applied to the optical fiber core housed in the optical fiber cable, the possibility that the optical fiber core wire, which is a glass material, breaks increases. Therefore, in order to suppress the tension applied to the optical fiber core wire below a certain level, a tensile member is provided as a constituent member of the optical fiber cable, and the tensile member is applied with the tensile member.

  In addition, a polyethylene-based resin is generally used as a material of an outer covering (cable outer covering) which is one of constituent members of an optical fiber cable. Since this polyethylene material has a larger coefficient of linear expansion compared to the optical fiber core, if the temperature changes in the usage environment, the entire cable will be stretched and tension will be applied to the optical fiber core accommodated in the cable. Or compression force will be added. Therefore, in the structure described in Patent Document 2, a tensile strength body is disposed inside the outer cover, and the expansion and contraction of the outer cover is suppressed.

  In addition, in the structure described in Patent Document 1, since it has a slot rod, it is easy to ensure mechanical strength, it is possible to reduce the thickness of the outer cover, and to suppress expansion and contraction of the outer cover due to temperature changes. Since there is no need, it was not necessary to arrange a tensile body in the outer jacket. On the other hand, in the structure described in Patent Document 2, it is necessary to increase the thickness of the outer cover from the viewpoint of ensuring mechanical strength. In order to suppress expansion and contraction of the outer cover due to temperature change, a tensile body is provided in the outer cover. There was a need to place.

  As the number of optical fiber cores accommodated in the optical fiber cable increases, the weight of the cable increases, and accordingly, a large traction force is required when laying the cable, but this also increases the tension applied to the cable. Therefore, it is necessary to thicken the tensile body.

  Here, in order to withstand a predetermined tension applied when laying the cable, the cross-sectional area of the strength member is required to be a certain level or more. Therefore, the tension equivalent to the tension that can be withstood by one tensile strength body arranged at the center of the cable as in Patent Document 1 is not provided with a plastic rod as in Patent Document 2, so that it is in the jacket. In order to secure with the two strength members arranged, it is necessary to secure an equivalent cross-sectional area for the strength members.

  That is, it is the same for the structure in which two strength members are arranged in a symmetrical position with the center of the cable sandwiched inside the cable jacket, and in the case of the structure in which one strength member is arranged at the center of the cable. Comparing the outer diameters of the strength members required to secure tension, the former case is about 0.7 times smaller than the latter case, but it is placed in a symmetrical position within the cable cross section. Therefore, the outer diameter is occupied about 1.4 times in total for the two.

  Therefore, in the structure of the optical fiber cable described in Patent Document 2, when the outer diameter of the strength member disposed inside the cable jacket is increased, the outer sheath is so thick as to wrap around the strength member. As a result, there is a problem that it is difficult to reduce the diameter of the cable.

  Patent Document 2 discloses a structure in which a strength member is disposed at the center of an optical fiber bundle constituting an optical fiber cable together with or in place of the outer sheath. However, in this structure, since the position of the strength member is not fixed in the cable cross section, the strength member that should be arranged at the center of the optical fiber bundle may move from the center position. In that case, since the tensile strength member is pressed against the optical fiber core and a lateral pressure is applied to the optical fiber core, there is a risk of increasing optical loss.

  Furthermore, in the optical fiber cable described in Patent Document 2, when the number of optical fiber cores to be accommodated is 1000 or more, many optical fiber core wires are accommodated in one space in the cable. For this reason, for example, there is a problem that the discrimination performance of the optical fiber core wire is deteriorated when the connection work is performed.

  In order to solve the above-described problems, the present invention includes at least a plurality of optical fiber core wires, a cable jacket, a first tensile body, a second tensile body, and a structure, The cover is provided with the second strength member along the longitudinal direction of the cable, and the first strength member can suppress the tension applied to the optical fiber core wire to a certain level or less when laying the cable. The second strength member has a property capable of suppressing expansion and contraction of the cable jacket caused by temperature change, and the structure has the first strength member over the entire length of the cable. A tension body holding portion for holding the cable, and extending radially from the strength body holding portion toward the cable jacket in the cross section of the cable, and extending the cable jacket through the entire length of the cable. In The first tensile body is held by the tensile body holder of the structure, and a plurality of optical fiber cores assembled together in a twisted or straight manner are separated from the partition wall of the structure. The present invention proposes an optical fiber cable in which a cable core is formed by being arranged between the parts, and the cable jacket is applied to the outer periphery of the cable core.

  ADVANTAGE OF THE INVENTION According to this invention, the optical fiber cable which can be laid without applying tension more than fixed to an optical fiber core wire, and was excellent in the core wire discriminability, and has many cores, a small diameter, and a high density.

Sectional drawing which shows an example of embodiment of the optical fiber cable of this invention

  Hereinafter, embodiments of an optical fiber cable of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing an example of an embodiment of an optical fiber cable according to the present invention. The optical fiber cable of the present invention includes an optical fiber core wire 1, a cable jacket 2, a first strength member 3, a second strength member 4, a structure 5, and an isolation layer 6.

  Here, the cable jacket 2 has a second strength member 4 disposed therein along the longitudinal direction of the cable. The first strength member 3 has a characteristic (mechanical strength) that can suppress the tension applied to the optical fiber core wire 1 to a certain level or less when the cable is laid, and the second strength member 4 has a temperature change. The cable jacket 2 has a characteristic capable of suppressing the expansion and contraction of the cable jacket 2.

  The structure 5 includes a tensile strength body holding portion 51 that holds the first strength body 3 over the entire length of the cable, and a radial direction from the strength body holding portion 51 toward the cable jacket 2 within the cross section of the cable. And a plurality of (three in the illustrated example) partition walls 52 that divide the inside of the cable jacket 2 in the cross section of the cable over the entire length of the cable.

  The isolation layer 6 has a cylindrical shape whose inner diameter is in contact with the tip of each partition wall 52 of the structure 5, and is provided between the cable jacket 2 and the structure 2 over the entire length of the cable.

  In the optical fiber cable of the present invention, the first strength member 3 is held by the strength member holding portion 51 of the structure 5, and a plurality of optical fiber cores 1 that are twisted together or gathered straight are connected to the structure 5. A cable core is formed between the partition walls 52 and a cable jacket 2 is applied to the outer periphery of the cable core via the isolation layer 6.

  By adopting such a structure, the tension applied when laying the cable can be handled only by the first strength member 3, so that the second strength member 4 embedded in the sheath 2 has a jacket due to a change in environmental temperature. Only the expansion and contraction of 2 should be suppressed. Therefore, it is not necessary to increase the outer diameter of the second strength member 4 so as to increase the jacket thickness. Although FIG. 1 shows an example in which two second strength members 4 are provided at symmetrical positions across the center of the cable, one or three or more may be provided.

  Further, the tensile strength body holding portion 51 that holds the first strength body 3 is supported at a substantially central portion in the cable jacket 2 by a plurality of partition walls 52 having substantially the same radial length. For example, even when an external force such as bending is applied to the cable, the first strength member 3 does not move greatly from the central portion in the cross section of the cable, and therefore the first strength member 3 is pressed against the optical fiber core wire 1. Therefore, an increase in optical loss can be made difficult.

  Furthermore, since the optical fiber core wire 1 is divided and accommodated in the cable core by the plurality of partition walls 52, the identification workability of the optical fiber core wire 1 is improved. FIG. 1 shows an example in which three partition walls 52 are provided at positions that are substantially equiangular with each other in the cable cross section, here 120 ° apart from each other. However, the number is not limited to three. It is good also as above.

  It is desirable that the optical fiber cable has a circular cross section in consideration of handleability and manufacturability. Furthermore, it is desirable to mount as many optical fiber cores as possible inside the outer sheath of the optical fiber cable having a circular cross section. In this case, the optical fiber is also applied to a region surrounded by a circle that is in contact with the tips of the plurality of partition walls 52, that is, a cross-sectional region that protrudes outward from the cross-sectional region obtained when the tips of the partition walls 52 are connected with straight lines. By mounting the core wire, more optical fiber core wires can be mounted. Therefore, by providing the isolation layer 6 as shown in FIG. 1, it is possible to improve manufacturability and workability when taking out the core wire.

  In addition, the optical fiber core wire 1 mounted on the optical fiber cable of the present invention can appropriately adjust the bending loss characteristic, the transmission characteristic, and the like. In other words, it is naturally possible to change the type of optical fiber to be mounted in order to obtain desired transmission characteristics. Also, the optical fiber core wire 1 can be mounted in a unit such as a tape shape or a circular shape in which a plurality of wires are integrated in consideration of connection workability, core wire distinguishability and manufacturability. Yes, it can be selected as appropriate.

  Further, since the cable jacket 2 and the isolation layer 6 are appropriately removed when the optical fiber core wire 1 is taken out, the cable jacket 2 and the isolation layer 6 are appropriately changed in order to facilitate removal in consideration of the workability. Can be added.

  In addition, the materials and dimensions of the cable jacket 2, the tensile strength members 3 and 4, the structure 5, and the isolation layer 6 are optical fiber cables such as mechanical characteristics, transmission characteristics, reliability, core line identification, and manufacturability. Various characteristics that are generally required may be considered, and the cable outer diameter and weight may be appropriately designed to be as small as possible.

  In particular, the dimensions of the first and second strength members 3 and 4, which are the characteristics of the present invention, can be designed in consideration of the balance with the traction tension at the time of cable laying and the expansion and contraction force due to temperature change. There is. Further, the number, shape, continuity in the longitudinal direction, and the like of the partition walls 52 of the structure 5 have room for designing in consideration of the core line distinguishability and manufacturability.

  Note that the strength body holding portion 51 and the partition wall portion 52 and the isolation layer 6 of the structure 5 do not necessarily have to be completely continuous in the longitudinal direction of the cable, and the strength body holding portion 51 does not support the first strength body 3. The partition wall portion 52 can support the strength member holding portion 51 at a substantially central portion of the cross section of the cable and can partition the plurality of optical fiber cores 1, and the isolation layer 6 can maintain the cable jacket 2 in a circular cross section. There may be a thinned (perforated) portion in the middle of the longitudinal direction.

  DESCRIPTION OF SYMBOLS 1: Optical fiber core wire 2: Cable jacket, 3: 1st strength body, 4: 2nd strength body, 5: Structure, 6: Isolation layer, 51: Strength body holding part, 52: Partition part .

JP-A-62-98313 Japanese Patent No. 4774337

Claims (3)

Comprising at least a plurality of optical fiber core wires, a cable jacket, a first strength member, a second strength member, and a structure;
In the cable jacket, the second tensile body is disposed along the longitudinal direction of the cable,
The first tensile body has a characteristic capable of suppressing the tension applied to the optical fiber core wire to a certain level or less during cable laying,
The second tensile body has a property capable of suppressing expansion and contraction of the cable jacket caused by a temperature change,
The structure includes a strength body holding portion that holds the first strength body over the entire length of the cable, a radial extension from the strength body holding portion toward the cable jacket in the cross section of the cable, and the cable. Consisting of a plurality of partition walls that divide the inside of the cable jacket over the entire length of the cable in the cross section of the cable,
The first strength member is held by the strength member holding portion of the structure, and a plurality of optical fiber cores that are twisted or gathered together are arranged between the partition walls of the structure to form a cable core. An optical fiber cable formed and provided with the cable jacket on the outer periphery of the cable core. 2. The optical fiber cable according to claim 1, wherein at least three of the partition walls are provided at positions that are substantially equiangularly spaced from each other in the cable cross section. In addition to the above
Between the cable jacket and the structure, a cylindrical isolation layer having an inner diameter that is in contact with the tip of each partition wall of the structure is provided over the entire length of the cable.
The optical fiber cable according to claim 1, wherein an optical fiber core wire is mounted inside the isolation layer.

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