JPH02114218A - Heat resistant coated optical fiber - Google Patents

Abstract

PURPOSE:To improve the lateral-pressure resisting property of the title optical fiber without lowering the heat resistance by providing a heat resistance pipe which freely incorporates the coated optical fiber in a circular hollow section formed in the direction of the optical axis of the coated optical fiber. CONSTITUTION:A coated optical fiber A is constituted of an optical fiber 4 and coated layer 5 and the coated optical fiber A is incorporated in a hollow section 6a of a heat resistant pipe 6. Therefore, even when the heat resistant pipe is bent by a lateral pressure, the coated optical fiber does not receive the lateral pressure and the radius of curvature of the coated optical fiber becomes larger than, at least, that of the heat resistant pipe in the state where the lateral pressure is applied to the pipe, resulting in the improvement in the lateral-pressure resistance of the coated optical fiber. Moreover, since no layer of a heat resistant resin, such as a fluorocarbon resin, is directly formed on the coated optical fiber, a deterioration in the heat resistance of the coated optical fiber caused by the contraction of the heat resistant resin due to a temperature change can be prevented. Therefore, the lateral-pressure resistance of the coated optical fiber can be improved without lowering the heat resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coated optical fiber used in a high temperature environment.

[Conventional technology]

As shown in FIG. 5, a conventional optical fiber core has a primary coating layer 2 covering an optical fiber 1 consisting of a core and a cladding;
Furthermore, it is configured to include a secondary coating layer 3 that covers this primary coating layer 2. The primary coating layer 2 is made of thermosetting resin such as silicone resin.

By the way, as the uses of optical fibers expand,
There is a demand for optical fiber cores (hereinafter referred to as "heat-resistant optical fiber cores") that can be used in high-temperature environments. As a heat-resistant optical fiber core, there is known an optical fiber core in which a secondary coating layer is formed of a fluororesin that is less thermally decomposed at high temperatures (Japanese Patent Laid-Open No. 56-44105).

Further, an optical fiber line in which the secondary coating layer 3 is formed of polyimide resin, polyethylene resin, etc. has been proposed.

Furthermore, there is an optical fiber core wire in which a fluororesin is directly coated on an optical fiber coated with a polyimide resin or a ladder-type silicone resin.

[Problem to be solved by the invention]

However, when a heat-resistant optical fiber coated wire having a secondary coating layer formed of a fluororesin is used at a high temperature of 150° C. or higher for a long period of time, there is a problem that thermal deterioration of the silicone resin occurs and transmission loss increases.

Furthermore, optical fiber coated with polyimide resin or ladder-type silicone resin has poor lateral pressure resistance, and there is a problem in using it as it is.

Furthermore, heat-resistant optical fiber cores in which polyimide resin is coated with fluororesin have a problem in that the fluororesin contracts due to temperature changes, resulting in increased transmission loss.

Therefore, an object of the present invention is to improve the lateral pressure resistance of a coated optical fiber without reducing the heat resistance of the optical fiber.

[Means to solve the problem]

In order to achieve the above object, the heat-resistant optical fiber core wire according to the present invention includes an optical fiber strand covered with a coating layer having a high thermal decomposition temperature, and a circular cavity formed in the optical axis direction of the optical fiber strand. A heat-resistant pipe that is freely stored in the interior of the body.

[Effect]

Since the present invention is configured as described above, even if the heat-resistant pipe is bent by lateral pressure, the optical fiber strand is not immediately subjected to lateral pressure. Therefore, the radius of curvature of the optical fiber becomes at least larger than that of the heat-resistant pipe when subjected to lateral pressure, and the lateral pressure resistance is improved.

In addition, since heat-resistant resin such as fluorine is not directly formed on the surface of the optical fiber, it is possible to prevent the heat-resistant resin from shrinking due to temperature changes and reducing the heat resistance of the optical fiber. Can be done.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heat-resistant optical fiber core according to the present invention will be described below with reference to the accompanying drawings. In the description, the same elements are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a cross-sectional view in the optical axis direction showing an embodiment of the heat-resistant optical fiber core according to the present invention. This invention basically includes an optical fiber 4, a coating layer 5, and a heat-resistant vibro.

The surface of this optical fiber 4 is coated with a coating layer 5, and the tip fiber 4 and the coating layer 5 constitute an optical fiber strand A. This optical fiber strand A is housed in the cavity 6a of the heat-resistant vibro by a vibration method, and the optical fiber strand A and the heat-resistant vibro constitute an optical fiber core.

The optical fiber 4 has, for example, a core diameter of 9 μm and a cladding diameter of 12 μm.
A 5 μm single mode optical fiber can be used.

The coating layer 5 has a thermal decomposition temperature of 200°C or higher and a Young's modulus of 50k.
It is made of a heat-resistant resin (polyimide resin, etc.) with a resistance of g/mm2 or more, and this coating layer 5 improves the heat resistance of the tip fiber strand A.

The heat-resistant vibro includes a circular cavity 6a having an inner diameter larger than at least the outer diameter of the optical fiber strand A, and the optical fiber strand A is housed inside.

This heat-resistant vibro is made of a material whose melting point and lateral pressure resistance are at least higher than those of the optical fiber strand A. In addition,
Since the optical fiber strand A is housed in the cavity 6a of the heat-resistant vibro, the heat resistance of the optical fiber strand A is not reduced, and the lateral pressure resistance can be improved. This heat-resistant pipe has an inner diameter of 0.7 mm and an outer diameter of 0.8 m.
m stainless steel can be used.

Note that this invention is not limited to the above embodiments. For example, the optical fiber is not limited to a single mode type, but may be a multimode type.

Further, the coating layer is not limited to polyimide resin, but may be a ladder-type silicone resin, a silicone resin as the primary coating layer, and a fluororesin as the secondary coating layer. The important thing is that the thermal decomposition temperature of the optical fiber is 200℃.
This is the point where the Young's modulus is 50 kg/mm2 or more.

Furthermore, the heat-resistant pipe is not limited to stainless steel, and may also be made of other metals other than stainless steel, ceramics, fluororesins, etc. In this case, it is not limited to a single body, but may be a composite body.

Note that the ratio of the inner diameter of the heat-resistant vibrator to the outer diameter of the optical fiber has an impact on lateral pressure resistance and heat resistance, so the ratio should be determined in consideration of the environmental conditions and manufacturing conditions in which the heat-resistant optical fiber is used. It changes depending on the situation.

Therefore, it goes without saying that the dimensional ratio shown in this embodiment is merely an example, and is not limited to this ratio. - For boat fishing, the outer diameter of the optical fiber is 2.5
Production efficiency is good if the heat-resistant pipe is configured with an inner diameter of ~5 times.

FIG. 2 is a process diagram showing the influence of lateral pressure when lateral pressure acts on the heat-resistant optical fiber core according to the present invention. Same figure (
A) is a cross-sectional view taken in the optical axis direction of a heat-resistant optical fiber coated wire to which no lateral pressure is applied. The tip fiber strand A is configured to be able to move freely within the circular cavity 6a of the heat-resistant vibro, so when no side pressure is applied, the heat-resistant pipe and the optical fiber strand A are in line contact in the optical axis direction. It is in.

Figure (b) shows a state in which lateral pressure is applied from above the heat-resistant vibro, and the heat-resistant vibro curves due to this lateral pressure load. However, since the optical fiber strand A is housed in the cavity 6a, it is not bent at this point.

Therefore, the lateral pressure resistance of the heat-resistant optical fiber core wire is enhanced by the heat-resistant pipe.

Figure (c) shows a state in which the lateral pressure load resistance is further increased. At this stage, the heat-resistant vibro and the optical fiber cable A are in three-point contact within the circular cavity 6a. In this case, since the optical fiber strand A receives lateral pressure from the center contact point, it begins to curve within the circular cavity 6a. Even in this case, the lateral pressure directly applied to the tip fiber cable line A is considerably alleviated. That is, the cavity provided in the heat-resistant vibrator improves the lateral pressure resistance of the heat-resistant optical fiber core wire.

However, if the inner diameter of the circular cavity 6a is too large with respect to the outer diameter of the optical fiber strand A, the extra length will become too large, and there is a risk that the optical fiber strand will meander within the cavity. Furthermore, if the two are too close together, manufacturing becomes difficult. As a practical ratio, it is desirable to set the ratio of the outer diameter of the optical fiber to the inner diameter of the heat-resistant pipe to 1:(2.5 to 5).

FIG. 3 shows experimental results regarding heat resistance and lateral pressure resistance. In this experiment, the optical fiber with a polyimide resin coating layer was wire A (white circle), the optical fiber wire with a ladder-type silicone resin coating layer was wire B (black circle), and the silicone resin coating layer was with wire B (black circle). The optical fiber cable line with the wire is shown as wire C (triangle). An optical signal with a wavelength of 1.55 μm is transmitted through the optical fiber wire placed in an environment of 200 degrees Celsius, and the change in loss is measured as yrl11. It is established.

Note that wire A is an optical fiber with an outer diameter of 125 μm coated with polyimide resin until the outer diameter is 160 μm, and wire B is an optical fiber with an outer diameter of 125 μm coated with ladder-type silicone resin until the outer diameter is 160 μm. The strand C is an optical fiber with an outer diameter of 125 μm and silicone resin coated with an outer diameter of 40 μm.
It is coated until it reaches 0 μm.

FIG. 3(a) shows experimental results showing the relationship between time and loss change in a high-temperature environment for coating layers made of different materials. According to this experiment, it can be seen that the transmission loss of the wire A1B does not increase even under high temperatures, but the loss of the wire C increases as time passes.

In the same figure (b), for coating layers made of different materials, strands A,
These are experimental results showing the relationship between the lateral pressure load applied by sandwiching the BSC between flat plates and the change in loss. According to this experiment, strand A,
It can be seen that the transmission loss of wire B increases when a lateral pressure load is applied, but wire C has good resistance to contralateral pressure.

As can be seen from the above experimental results, if these coating layers have good heat resistance, they have poor lateral pressure resistance, and if they have good lateral pressure resistance, they have poor heat resistance. Therefore, the present invention further improves the inherent heat resistance and lateral pressure resistance of the optical fiber by storing the optical fiber in a freely movable state within a heat-resistant vibro.

FIG. 4 shows experimental results regarding lateral pressure resistance and heat resistance of the heat-resistant optical fiber core wire according to the present invention. FIG. 1(a-) shows the relationship between the lateral pressure load applied by sandwiching the heat-resistant optical fiber shown in FIG. 1 between flat plates and the change in loss. According to this experiment, the lateral pressure load was 300
It can be seen that no lateral pressure is applied to the optical fiber up to [kg 15 cm], and the lateral pressure resistance is significantly improved.

FIG. 4B shows the relationship between temperature and loss change. According to this experiment, Ti loss did not increase even when the temperature rose from 140°C to 200°C.2. It can be seen that it has good heat resistance.

〔Effect of the invention〕

Since this invention is configured as explained above,
The lateral pressure resistance can be improved without reducing the heat resistance of the optical fiber strands housed in the heat-resistant pipe.

Furthermore, it has stable transmission characteristics against temperature changes (-40° C. to 200° C.) (see FIG. 4(b)), and can improve reliability against temperature.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view from the optical axis direction showing an embodiment of the heat-resistant optical fiber core according to the present invention, and FIG. 2 is a process diagram showing the influence of lateral pressure on the heat-resistant optical fiber core according to the present invention. , FIG. 3 is a diagram showing experimental results regarding heat resistance and lateral pressure resistance, FIG. 4 is a diagram showing experimental results regarding lateral pressure resistance and heat resistance of the heat-resistant optical fiber core wire according to the present invention, and FIG. 1 is a sectional view taken from the optical axis direction showing a conventional optical fiber core. 1.4...Optical fiber 2...Primary coating layer 3...Second coating layer 5...Coating layer 6...Heat-resistant pipe A...Optical fiber strand patent applicant Sumitomo Electric Industries, Ltd. Agent Patent Attorney Co., Ltd. Haseyo Yoshikima
Mountain 1) Row heat-resistant optical fiber core wire No.] Figure 5 Conventional technology Figure 5 Shadow of lateral pressure i Figure 2 Interval (week) Weight [0cm] Experimental results (+/2) Figure Weight 2■ [g75cm] Experimental results (2//2)

Claims (1)

[Claims] 1. An optical fiber strand covered with a coating layer having a high thermal decomposition temperature, and the optical fiber strand is freely housed in a circular cavity formed in the optical axis direction. A heat-resistant optical fiber core comprising a heat-resistant pipe. 2. The coating layer has a thermal decomposition temperature of 200°C or higher, 50k
The heat-resistant optical fiber core wire according to claim 1, having a Young's modulus of g/mm^2 or more.