JPS6289915A - Optical fiber unit - Google Patents

Abstract

PURPOSE:To suppress the transmission loss due to the fatigue degradation of an optical fiber and the side pressure or compressive strain by constituting outermost layers of optical tape cores, which are laminated and stored in a groove of a spacer, with coating layers which have <=30mum thickness and consist of materials having a low coefficient of static friction. CONSTITUTION:A coefficient mu of static friction of surfaces of optical tape cores used in an optical fiber unit having the spacer structure is set to <=0.9, and thereby, a relaxation rate Aepsilon of a maximum distortion for bend of the optical fiber unit is <=0.2 to suppress the distortion to a very small value and this optical fiber unit is superior in transmission loss characteristic to bend. The layer thickness of the outermost layer of the tape core is set to <=30mum to reduce influences upon physical characteristics such as Young's modulus of the coating material. Since this layer thickness if <=30mum and thin, dimensions of this optical tape core are hardly different from those of an optical tape core which is not provided with a layer having a low coefficient of static friction.

Description

[Detailed description of the invention] [Summary of the invention] In the groove of the spacer with 11.
．． By housing a laminate of tape-shaped optical fiber cores with a thickness of 9 or less, the maximum strain relaxation rate during bending is 0.2 or less, and fatigue deterioration and elongation strain of the optical fiber due to long-term bending after installation are reduced. Optical fiber Unisoto suppresses the increase in transmission loss due to lateral pressure or compressive strain caused by.

[Industrial application field]

The present invention relates to an optical fiber unit in which a laminate of tape-shaped optical fiber cores (hereinafter referred to as optical tape cores) is housed in a spiral groove of a rod-shaped spacer, and in particular to an optical fiber unit with excellent bending properties. be.

[Conventional technology]

This type of rod-shaped spacer has a structure in which the optical tape fiber laminate is housed in a spiral groove (hereinafter referred to as a spacer structure). It has excellent features such as:

[Problem that the invention seeks to solve]

When an optical fiber unit with a spacer structure is bent, elongation strain occurs in the optical fiber located on the outside of the bend.
Compressive strain occurs in the optical fiber located in the bent inner portion.

Since elongation strain promotes the elongation of cracks on the optical fiber surface,
Continuing to apply large strains for a long period of time is undesirable from the standpoint of long-term reliability. Further, since the optical fibers 1 to 1 with the spacer structure have a structure in which the optical fiber core wire laminate is wound, lateral pressure is applied to the optical fibers when elongation strain occurs. Therefore, it is necessary to suppress the elongation strain to a small level in view of the increase in transmission loss due to lateral pressure.

For this purpose, it is necessary to investigate the relationship between the bending diameter when the optical fiber unit is bent and the maximum elongation strain at that time.

When the optical fiber unit has a normal tight structure, the maximum strain εC due to bending can be calculated using the following equation.

Here, a is the layer core diameter and R is the bending radius.

However, in the case of the spacer structure, although it is a tight structure, it is a structure in which the optical tape cable can move in the longitudinal direction within the groove, so it is thought that the strain is relaxed in the longitudinal direction and the maximum strain is small.

The strain caused when the optical fiber unit is bent can be investigated by sequentially winding the optical fiber unit around a mandrel and monitoring the change in the length of the optical fiber at that time. That is, when the optical fiber unit 7) is bent, the strain distribution within the optical fiber unit 7) can be expressed by the following equation. (For example, Kokubu et al.: 1985 IEICE All Universities 227
5) Here, ε is the maximum strain, p is the spacer groove pitch, and θ0
is a constant representing the fiber position at x=O.

At this time, the length change Δl when the optical fiber unit is wound around the mandrel by length X is expressed by the following equation.

Therefore, by actually measuring Δl(A, it is possible to know the value of ε. The relaxation rate A5 of the maximum strain when the optical fiber unit is bent can be expressed by the following equation.

Aε-ε-/εc (4) When an optical fiber unit with a spacer structure is bent, it is desired to realize an optical fiber unit with a spacer structure that has a small maximum strain relaxation rate Aε.

[Means for solving problems]

The present invention provides an optical fiber unit having a spacer structure with a small maximum strain relaxation rate Aε when bent. It is characterized by being composed of a coating layer made of a material with a small coefficient of static friction of 30 μm or less.

[For production]

The present invention reduces the coefficient of static friction on the optical tape core surface,
In particular, by setting it to 0.9 or less, the maximum strain relaxation rate when the optical fiber is bent is 0.2 or less, and fatigue deterioration of the optical fiber after installation and lateral pressure or compressive strain caused by elongation strain can be prevented. Increase in transmission loss can be minimized. This will be explained below using examples.

〔Example〕

The strain relaxation rate was measured for an example using the tape core wire of the present invention in a tape core wire spacer cable whose cross-sectional structure is shown in FIG. In Figure 1, 1 is a grooved spacer, 2 is a groove,
3 is an optical tape core, 4 is a pressure tape, 5 is a cable sheath, and 6 is a tensile strength member.

The strain relaxation rate was measured using a tape core wire spacer cable using the following four types of optical tape core wires.

Optical tape core I: width 1.6 nm, thickness 0.45 mm
This is a 5-core optical tape core, and the coating material is ultraviolet curing resin.

[Conventional optical tape core]

Optical tape core ■: Coloring agent is applied to the surface of optical tape core I.

[Embodiment 1 of the present invention] Optical tape core ■: Solvent-soluble nylon was applied to the surface of optical tape core I. [Embodiment 2 of the present invention] Optical tape batting ■:
Apply Teflon to the surface of the optical tape core I. [Embodiment 3 of the present invention] The coefficient μ of static friction on the surface of each of these four types of optical tape cores is as follows.

Optical tape core wire 1. A tape core spacer cable was prototyped in which the outer diameter of the grooved spacer 1, whose cross-sectional structure is shown in FIG. 1, was 9 mmφ and the outer diameter of the cable sheath was 14 mmφ. Next, these four types of tape core spacer cables were made into a diameter of 500 m.
Wrap each 200 mm length around a mφ mandrel, and use the phase method to measure the change in length for the five fibers #1 to #5 of the optical tape cores located in the outermost layer of each tape core spacer cable. I monitored it. At this time, sample 4
A variety of optical tape cores and a tape core spacer cable were fixed at both ends, and the modulation frequency was set to 500 MHz. Determine the maximum strain ε℃ in the spacer structure from the obtained waveform,
The strain relaxation rate Aε (river) at the static friction coefficient μ was calculated. The results are shown in FIG. 2. As can be seen from FIG. 2, the relaxation rate A5 (/i) can be expressed by the following equation.

From equation (5), when the static friction coefficient μ=0.9, the relaxation rate A
It can be seen that ε(0,9) is 0.2.

Next, one type of sample tape core wire spacer cable was bent to a bending diameter of 200 mm, and the change in transmission loss due to bending was actually measured. The actual measurement results are shown in Figure 3.

In the case of a conventional tape fiber spacer cable using an optical tape fiber (2) with a coefficient of static friction of 3.21, a 10 loss increase of 0.2 to 0.6 was observed from the minimum to the maximum (value).

In contrast, the static friction coefficient according to the present invention is 0.
89.0.65.0,44 optical tape cable U, II
In the case of tape core spacer cables using 1 and 2, no increase in loss was observed.

From the above actual measurement results according to the embodiments of the present invention, it has been found that by setting the static friction coefficient μ of the surface of the optical tape used in the spacer-structured optical fiber unit to 0.9 or less, the maximum strain when the optical fiber unit is bent is reduced. By setting the relaxation rate A5 of 0.2 or less, strain can be suppressed to a sufficiently low level, and an optical fiber unit with excellent transmission loss characteristics against bending can be obtained. It was confirmed that the effect on physical properties was small.

In addition, since this layer is a thin layer with a thickness of 30 μm or less,
Dimensionally, it is almost the same as a conventional optical tape core without a conventional low static friction coefficient layer.

In the embodiments described above, a coating with a low coefficient of static friction is applied to both sides of the outermost layer of the tape core wire, but it is equivalent in the present invention even if it is applied only to one side. be.

〔Effect of the invention〕

As described above, according to the present invention, a coating layer having a static friction coefficient of 0.9 or less is provided on the outermost layer of the ribbon core, and the relaxation rate of maximum strain when the optical fiber unit is bent is 0.9. 2
By setting the strain as follows and reducing the strain, it is possible to minimize fatigue deterioration of the optical fiber due to bending over a long period of time after installation, and increase in transmission loss due to lateral pressure or compressive strain caused by elongation strain.

In addition, by setting the thickness of the outermost layer to 30 μm or less, the influence on the physical properties such as the Young's modulus of the coating material is reduced, and it is also dimensionally similar to conventional tape cores without coating with a low coefficient of static friction. It's no different.

[Brief explanation of drawings]

Fig. 1 shows the cross-sectional structure of the tape cable spacer cable whose strain relaxation rate was measured, Fig. 2 shows the actual measurement results of the friction coefficient and relaxation rate of the tape cable according to the conventional and the present invention, and Fig. 3 shows the results of the conventional and the present invention. This is the actual measurement result of the static friction coefficient of the tape core wire and the increase in transmission loss due to bending. 1... Spacer with/l ■, 2... Groove, 3... Optical tape core wire, 4... Holder winding tape, 5... Cable sheath, 6... Tensile strength body patent applicant Sumitomo Denki Kogyo Co., Ltd. (1 other person) Agent Patent attorney Tama Mushi Kyugobe No. 1 Figure I/πp stop ff4 rub (rope (HJ!! coefficient of side tape knotted wire!! Actual measurement of pulling sum ratio [result tube
2 Figure 1/ Static friction lock (μ) Static friction coefficient of tape IL wire and loss due to bending 0 actual immersion 1 results Figure 3

Claims (5)

[Claims] (1) In an optical fiber unit in which a laminate in which a plurality of tape-shaped optical fiber cores are stacked in the radial direction of the bar-shaped spacer is housed in a plurality of grooves spirally provided on the outer peripheral surface of the bar-shaped spacer. , an optical fiber unit in which the outermost layer of each of the tape-shaped optical fiber cores is coated with a coating layer of a material having a small coefficient of static friction and having a thickness of 30 μm or less. (2) The optical fiber unit according to claim 1, wherein the coating layer is made of a colorant, Teflon, or solvent-soluble nylon. (3) The optical fiber unit according to claim 1, wherein the surface of each of the tape-shaped optical fiber cores has a coefficient of static friction of 0.9 or less. (4) The optical fiber unit according to claim 1, 2 or 3, wherein the second coating layer from the outermost layer of the coating of each of the tape-shaped optical fiber cores is made of an ultraviolet curable resin. . (5) Claims 1, 2, 3 or 3, wherein the outermost coating layer of the tape-shaped optical fiber is applied only to one surface of the tape-shaped optical fiber. The optical fiber unit according to item 4.