JP2006337705A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable in which unnecessary stress caused in optical fiber core side is suppressed by optimizing the respective friction coefficients between the fiber core and an inclusion, and between the inclusion and a sheath. <P>SOLUTION: In the optical fiber cable 100A, the outer periphery of the fiber core 110 is coated with the sheath 130 via the inclusion 120, and the friction coefficient μ1 between the fiber core 110 and the inclusion 120 is smaller than the friction coefficient μ2 between the inclusion 120 and the sheath 130. Thus, a space between the inclusion 120 and the sheath 130 are less slippery, the expansion and the contraction due to an external load and a temperature change are effectively absorbed between the inclusion 120 and the sheath 130, and the influence of the expansion and the contraction on coated optical fibers and coated optical fiber tapes is excellently suppressed since the friction coefficient μ1 between the fiber core 110 and the inclusion 120 is small. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical cable in which a decrease in transmission characteristics can be satisfactorily suppressed by optimally adjusting respective friction coefficients between a core core and an intervening and between an intervening and a sheath.

  In recent years, a slotless structure has been proposed as an optical cable structure. The slotless structure means a structure without a slot having a slot (groove) for accommodating an optical fiber core or an optical fiber tape core in the longitudinal direction of a cylindrical long body that is usually rich in rigidity. It can be said that the structure is superior in terms of flexibility and flexibility.

  However, in the case of the slotless structure, since the interposition is in direct contact with the core core portion made of the optical fiber core or the optical fiber tape core, the core core side, that is, the optical fiber core The optical fiber ribbon is constrained.

  For this reason, when an optical cable is bent in laying a cable or the like, there is a possibility that a local bend occurs in the optical fiber core or the optical fiber tape core, or a minute bend is applied to cause transmission loss. Even when the optical cable is not bent, the cable itself expands and contracts if there is a temperature fluctuation in the installed state (wired state). Therefore, the optical fiber core on the side of the core core with a low linear expansion coefficient with respect to the cable sheath. A large stress (tensile force or compressive force) is applied to the wire or the optical fiber ribbon, and transmission loss, so-called microbend loss occurs.

However, in the past, no effective measures have been taken for such a situation. However, in an optical cable, a method for obtaining a coefficient of friction with other components such as an optical fiber core or a method for obtaining a retention force such as an optical fiber core (Patent Documents 1 and 2) is partially proposed. Has been.
JP-A-2005-0555704 JP-A 61-056932

  Accordingly, the present inventors have focused on the frictional force between the constituent members of the optical cable and conducted various experiments by changing the friction coefficient between the constituent members. As a result, the optical fiber core wire or the optical fiber tape core wire was obtained. When the friction coefficient μ1 between the core core and the interstitial is smaller than the friction coefficient μ2 between the interstitial and the sheath (μ1 / μ2 <1), an external force such as bending is applied to the optical cable in the installed state, or the temperature fluctuates. It has been found that even if there is, there is a good reduction in transmission characteristics.

  In other words, even if there is an external force load or temperature fluctuation and the cable itself expands and contracts, the above relationship of μ1 / μ2 <1 is established, that is, the friction coefficient μ2 between the interposition and the sheath is Since the friction coefficient μ1 is greater than the friction coefficient μ1, it is difficult for the interposition and the sheath to slip, and the expansion and contraction due to the load of external force generated between the interposition and the sheath and the temperature variation are effectively absorbed. In other words, it is possible to prevent the intervention from stretching or staying locally. On the other hand, it is presumed that the influence on the side of the core wire core can be suppressed because the friction coefficient μ1 between the core wire core and the interposition is small.

  The present invention has been made based on such a new idea. Basically, the friction coefficient μ1 between the core core and the interposition is made smaller than the friction coefficient μ2 between the interposition and the sheath (μ1 / μ2). <1) Deterioration of transmission characteristics An optical cable that can satisfactorily suppress a decrease in transmission characteristics is provided.

  According to the first aspect of the present invention, in the optical cable in which a sheath is coated on the outer periphery of the core core through the intervention, the friction coefficient μ1 between the core core and the intervention is smaller than the friction coefficient μ2 between the intervention and the sheath. It is in the optical cable characterized by being.

  According to a second aspect of the present invention, there is provided the optical cable according to the first aspect, wherein the core core is composed of one or a plurality of optical fiber cores.

  According to a third aspect of the present invention, there is provided the optical cable according to the first aspect, wherein the core core is composed of one or a plurality of optical fiber ribbons.

  In the present invention, in the optical cable, since the friction coefficient μ1 between the core core and the interposition is smaller than the friction coefficient μ2 between the interposition and the sheath, an external force such as bending is applied to the optical cable in the installed state, or the temperature Even if there is a fluctuation, it is possible to suppress a decrease in transmission characteristics.

FIG. 1 shows an embodiment of an optical cable according to the present invention.
In the optical cable 100A, the core core side is composed of a plurality of optical fiber cores. In the figure, 110 is a core core (for example, an 8-core assembly core core) made up of a plurality of optical fiber cores 111. 140 and 140 are tension members made of a steel wire or high-tensile plastic fiber placed in the longitudinal direction of the sheath 130. The number of optical fiber cores of the core core 110 can be singular.

  In this optical cable 100A, the friction coefficient μ1 between the core core 110 and the interposition 120 is smaller than the friction coefficient μ2 between the interposition 120 and the sheath 130. Here, the combination of the materials used on the core core side, the intervening side, and the sheath side is not particularly limited, and as a result, the relationship of μ1 / μ2 <1 may be satisfied.

  For example, in an ordinary optical fiber, an ultraviolet curable resin is used as the outermost layer resin material, so a polypropylene yarn is used as an intervening material, and polyethylene (for example, LLDPE) is used as a sheath material. What is necessary is just to establish the said relationship. Further, when coating the outer surface of each constituent member, it is necessary to establish the above relationship in consideration of the friction coefficient between the coating material and the counterpart member.

  When the relationship of μ1 / μ2 <1 is established in this way, as described above, the friction coefficient μ2 between the intervention and the sheath is larger than the friction coefficient μ1 between the core core and the intervention, so Is difficult to slip, and expansion and contraction due to external force load and temperature fluctuation generated between the intervention and the sheath are effectively absorbed between the intervention and the sheath, while the coefficient of friction μ1 between the core core and the intervention is small, It is presumed that the influence on the core core side is satisfactorily suppressed.

FIG. 2 shows an embodiment of the optical cable according to the present invention.
In the optical cable 100B, the core core side is composed of a plurality of optical fiber ribbons. In the figure, 110 is a core core (for example, a three-layer assembly core core) composed of a plurality of optical fiber ribbons 112, 120 is an interposition provided on the outer periphery of the core core 110, and 130 is an interposer 120. The sheaths 140 and 140 covered on the outer periphery are tension members made of steel wire or high-tensile plastic fiber inserted in the longitudinal direction of the sheath 130. The number of the optical fiber ribbons of the core core 110 may be singular.

  In this optical cable 100B, the friction coefficient μ1 between the core core 110 and the intervention 120 is smaller than the friction coefficient μ2 between the intervention 120 and the sheath 130. Here, the combination of the materials used on the core core side, the intervening side, and the sheath side is not particularly limited as in the case of FIG. 1, and as a result, if the relationship of μ1 / μ2 <1 is established. Good.

  For example, in an ordinary optical fiber ribbon, an ultraviolet curable resin is used as the outermost layer resin material, so a polypropylene yarn is used as an intervening material, and polyethylene (for example, LLDPE) is used as a sheath material. Thus, the above relationship may be established. Further, when coating the outer surface of each component member, it is necessary to establish the above relationship in consideration of the friction coefficient between the coating material and the counterpart member.

  Also in this optical cable 100B, when the relationship of μ1 / μ2 <1 is established, the same operation and effect as the optical cable 100A in FIG. 1 can be obtained.

  Incidentally, three types of sample cables having the same structure as the optical cable 100A of FIG. 1 were manufactured, and μ1 and μ2 of each cable were set as shown in Table 1, and the transmission loss was obtained. It was. Here, the optical fiber core wires of the sample cables 1 to 3 are made of a 125 μm-diameter bare glass fiber coated with an ultraviolet curable resin to a diameter of 250 μm. Further, as the interposition, the sample cable 1 uses polypropylene yarn, the sample cable 2 uses aramid fiber, the sample cable 3 uses rubber fiber, and the sheath uses the sample cable 1 as polyethylene (LDPE) and the sample cable 2 as polyethylene ( LLDPE) and polyethylene (HDPE) were used in the sample cable 3. Moreover, about the transmission loss of each sample cable 1-3, the transmission loss at the time of a temperature fluctuation | variation was calculated | required using the laser beam of wavelength 1.55 micrometer.

  From Table 1 above, it can be seen that the relationship of μ1 / μ2 <1 of the present invention is established, and that the transmission loss decreases as the value of μ1 / μ2 decreases. In other words, it can be seen that the transmission loss increases when μ1 / μ2> 1. Even when an external force is applied, it can be easily estimated that the same result as that at the time of temperature fluctuation can be obtained because the friction coefficient μ2 side between the interposition and the sheath is large.

1 is a longitudinal end view of an optical cable according to an embodiment of the present invention. It is a vertical end view which becomes other embodiment of the optical cable which concerns on this invention.

Explanation of symbols

100A to 100B ... Optical cable, 110 ... Core wire core, 111 ... Optical fiber core wire, 112 ... Optical fiber tape core wire, 120 ... Intervene, 130 ... Sheath, 140 ...・ Tension member

Claims (3)

An optical cable in which a sheath is coated on an outer periphery of a core core through an interposition, wherein a friction coefficient μ1 between the core core and the interposition is smaller than a friction coefficient μ2 between the interposition and the sheath. . The optical cable according to claim 1, wherein the core core is composed of one or more optical fiber core wires. 2. The optical cable according to claim 1, wherein the core core is composed of one or a plurality of optical fiber ribbons.

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