JPS63175813A - Metal coated optical fiber core - Google Patents

Abstract

PURPOSE:To obtain a metal coated optical fiber core which is superior in water pressure resistance, lateral pressure resistance, and tension resistance though having a small diameter, by making the resistance temperature of fibers of this core equal to or higher than the melting point of a low-melting point alloy. CONSTITUTION:Plural optical fiber strands 3 in each of which at least one buffer layer 2 is provided around a glass fiber 1 for optical transmission are gathered in concentric circles or in parallel, and fibers 6 longitudinally or spirally arranged continuously in the lengthwise direction are provided around this gathering, and a metallic coating layer consisting of the low-melting point alloy having <=250 deg.C melting point is provided around these fibers 6. With respect to this metal coated optical fiber core, the resistance temperature of fibers 6 is equal to or higher than the melting point of the low-melting point alloy. Thus, the metal coated optical fiber core is obtained which has sufficient hydrogen cutoff property, pressure resistance, water pressure resistance, and tension resistance regardless of the small diameter and is superior in productivity of long-sized products and has a small loss.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a small diameter and can be used in a hydrogen environment, under lateral pressure, under water pressure,
The present invention also relates to a low-loss original fiber core with excellent optical transmission stability under tensile loads.

[Conventional technology]

Optical glass fibers used as optical transmission media usually have a diameter of less than α2W and are made of brittle materials, so scratches can easily occur on the surface, and these scratches can become a source of stress concentration, causing external forces to be applied. If it is, it will easily break. Further, when an external force such as lateral pressure acts on the glass fiber and microbends occur in the fiber, optical transmission loss increases.

For this reason, generally, as shown in the cross-sectional view in FIG.
Then, a hard plastic coating layer 4t with a Young's modulus of about 50 IV/fi is applied, and the core fiber is treated as a core fiber 5 with an outer diameter of α3 to 1.Rho.Furthermore, the core fiber is made into a cable and used outdoors, etc. used in

However, it is known that when moisture gets mixed into the cable, the moisture is electrolyzed by local battery action that occurs between the metal materials that make up the cable, and hydrogen is generated. When plastic is used as the material for the buffer layer and the covering layer, the diffusion coefficient of hydrogen in plastic is approximately 1O.
-s-78 is about 1000 times larger than the diffusion coefficient in metal materials, and hydrogen easily permeates through these materials.
A drawback is that hydrogen reacts with defects in the quartz glass, resulting in increased optical loss. Also, the Young's modulus of plastic is usually 50.
Since it is lower than 0 K/i 7w'' and is lower than that of metal materials, it has the disadvantage that when large lateral pressure or water pressure acts on the original fiber core i, the coating layer is crushed and optical loss increases.

In order to compensate for these drawbacks, a method is used in which metal coating is applied directly to the outer periphery of the original fiber by vapor deposition or vacuum plating, as described in Japanese Patent Application Laid-open Nos. 57-145044 and 57-111266. Ta. However, as shown in the cross-sectional view in FIG. 10, these structures do not have a buffer layer between the surface of the original fiber 1 and the metal coating layer 7, so when coating the original fiber with the metal layer, microscopic This method has disadvantages in that bends occur and it is difficult to manufacture a core fiber core with low loss. - As an example, the loss of aluminum-coated optical fiber, which currently has the lowest loss, is about 106 B/krn at a wavelength of 1.3 μm, and it is difficult to achieve a lower loss with the current technology.

On the other hand, as described in Japanese Patent Publication No. 5B-9054, a silicone buffer layer 2 is applied around the original fiber 1, and a core wire 5 having the structure shown in FIG.
The loss is approximately 155 aB/km, and a low-loss core wire almost equal to the theoretical limit of the original fiber has been realized.
A buffer layer is indispensable in order to realize a low-loss original fiber core. A structure has also been proposed in which the original fiber is embedded within the metal strip by processing the metal strip.

The structure described in JP-A-56-53602 and JP-A-56-78802 is shown in FIGS. Although a formed metal tube 10 is used, it is difficult to prevent hydrogen from entering from the abutting portion.It is possible to seal the abutting portion by brazing or welding to prevent hydrogen from entering. However, in this case, the temperature of the metal coating layer increases during the manufacturing process, which may damage the properties of the original fiber or core plastic material inside the metal coating layer. The limit for reducing the diameter is about 2 diameters, and there is a drawback that it is difficult to reduce the diameter further.

Even when a cold-drawn or cold-pressed tube is used as the metal coating layer, the inner diameter is limited to about 2W in order to suppress the temperature rise inside the metal coating layer, making it difficult to manufacture long tubes. .

Furthermore, the structure described in Japanese Patent Application No. 61-50356 includes a plastic buffer layer 2 provided around the original fiber 1, as shown in the cross-sectional view in FIG. The metal coating layer 7 is formed by
There is no metallic bond or chemical bond between the plastic buffer layer 2 and the low melting point alloy, so the adhesive force is weak, and the surface of the plastic buffer layer 20 is smooth, so the frictional force is small, and a stable metal coating layer is continuously formed. It's difficult to do. Furthermore, the Young's modulus of low melting point alloys is usually 5000 Kll/v.
m'' or less, the metal coating layer must be made thicker to prevent the metal coating layer from breaking when tension is applied, which has the disadvantage of impairing the ability to reduce the diameter of the core wire. there were.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a metal-coated fiber core wire that has a small diameter, has sufficient hydrogen barrier properties, pressure resistance, water pressure resistance, and tensile resistance, has excellent long-length manufacturability, and has low loss. It is in.

[Means for solving problems]

To summarize the present invention, the first invention of the present invention relates to a metal-coated fiber core wire, which includes at least one buffer layer surrounding an optical transmission gas fiber, which is continuous in the longitudinal direction. In a metal-coated fiber core wire having fibers arranged longitudinally or spirally, and a metal coating layer of a low-melting point alloy having a melting point of 250°C or less surrounding the fibers, the heat resistance temperature of the fibers is The melting point is equal to or higher than the melting point of the alloy.

The second invention of the present invention relates to another metal-coated fiber core wire, in which a plurality of original fiber wires each having at least one buffer layer applied around an optical transmission glass fiber are arranged in a concentric or circular shape. A metal-coated layer fiber having fibers arranged in a vertical or spiral manner continuously in the longitudinal direction around an aggregate assembled in parallel, and a metal-coated layer of a low-melting point alloy having a melting point of 250°C or less around the fibers. The core wire is characterized in that the allowable temperature limit of the fiber is equal to or higher than the melting point of the low melting point alloy.

In the present invention, at least one buffer layer made of soft plastic or the like is applied around the original fiber to form the original fiber, and a long fiber such as aramid fiber having a heat resistance temperature equal to or higher than the melting point of the metal coated thereon is used. The material is vertically spliced or spirally wound, and a coating layer made of a metal material is applied around it.The metal coating method does not use welding forming technology of butt tubes, but uses a buffer layer such as plastic and heat treatment of long fibers. Ninth, to prevent deterioration, a low melting point alloy having a melting point of 250° C. or less is coated by extrusion or vapor deposited.

The metal-coated fiber core of the present invention differs from conventional metal-coated optical fiber cores in that it has excellent tensile properties and can be manufactured in long lengths, and the outer diameter of the core can be reduced. have

The metal coated fiber core wire is produced, for example, by a method of solidifying a molten low melting point alloy in a die and drawing it from below, as in the previously proposed ``original fiber metal coating device''. A schematic diagram of the creation method is shown in Figure 2. 8 is a die. When the plastic-coated original fiber strand 3 is directly coated with a low-melting-point alloy, the adhesive force between the original fiber and the low-melting-point alloy is such that there is no metallic bond or chemical bond, and the surface of the plastic-coated optical fiber is Due to its smoothness, the frictional force between the inner surface of the die and the low melting point alloy is not large enough. It is easy to cut due to the frictional force, and it is difficult to obtain a long metal coated fiber core wire.

However, when aramid fibers, for example, are attached vertically to the original fiber wire, the low melting point alloy is wrapped around the fine aramid fiber filaments, resulting in a large contact area and poor adhesion. If the frictional force between both fiber layers and the low melting point alloy is sufficiently larger than the frictional force between the inner surface of the die and the low melting point alloy, the low melting point alloy that has begun to solidify will not be cut and a metal coating layer will be formed well. be done.

In addition, the aramid fiber layer is stable up to about 200℃,
It is not attacked by the low melting point alloy in the molten state, and the Young's modulus of the aramid fiber is 13,000 Y/-, which is higher than the Young's modulus of the original fiber, which is 7,290 Y/-, and it is the same as that of the metal-coated optical fiber core. Tensile strength properties are improved.

It is estimated that if the melting point of the alloy exceeds about 250° C., the properties of the silicone resin, which is the most heat-resistant buffer layer material, will be impaired. Therefore, the melting point of the metal coating layer 7 is 250°C.
The following settings are required.

The transmission loss of the original fiber with this structure is 1.3 μm in wavelength.
The loss was approximately 42 dB/km, which is sufficient for practical use.

Figure 3 is a graph showing the calculated relationship between the buckling water pressure (atmospheric pressure, vertical axis) of the core fiber coating layer and the outer diameter of the core (horizontal axis) when water pressure is applied to the original fiber core. Shown as In the figure, the solid line indicates gold when a low melting point alloy is used for the coating layer, and the broken line indicates gold when nylon is used for the coating layer. However, Young's modulus is 3000 for each
VJj /ym'' and 9/■2 to 100, and the inner diameter of the coating layer was α4mφ.In contrast to the case of a nylon coated core wire with an outer diameter α9mφ, the coating layer buckles at about 500 atm.
The alloy coated core wire can withstand water pressure of about 3000 atmospheres even with an outer diameter of 0.6vaxφ, making it possible to reduce the outer diameter of the core wire and significantly improve the water pressure resistance. The following formula was used for calculation◇
゛Here, P: Buckling water pressure of the coating layer E: Young's modulus of the coating layer: Poisson's ratio of the coating layer (approximately α55) t: Thickness of the coating layer d: Outer diameter of the coating layer and permeation of hydrogen into the fiber The degree of diffusion is proportional to the diffusion coefficient of the coating layer, but generally the diffusion coefficient of metal is about 1/10" to 1/10' compared to plastic. For example, at room temperature 25 ° C.
The diffusion coefficient of hydrogen in polyethylene is 50×10″
″6ctl/sec, iron f x 88 x 10-1
0i/sec, 5.71 x 10-9275 for aluminum. For this reason, in a core wire coated with metal, it is possible to coat the periphery of the base metals without any gaps, so that hydrogen can be sufficiently blocked, and the core wire can be used even in a hydrogen atmosphere without increasing the base strength.

FIG. 4 shows the elongation characteristics when tension is applied to the original fiber core wire as a graph of the relationship between tension (kgfs vertical axis) and elongation strain (%, horizontal axis). However, the outer diameter of the buffer layer is (L
4 m+, and the outer diameter of the core wire was 19 cod. In the figure, the solid line indicates the case where only a low melting point alloy is used for the coating layer, the dashed line indicates the case where 2280 denier Kevlar 49 is applied vertically around the buffer layer and the low melting point alloy is coated around it, and the dashed line indicates the case where nylon is used as the coating layer. The case where it is used is shown. However, Young's modulus is low melting point alloy 3
000 Kll / ll11”% Kevlar 49 is 1
200 [1 Y/-, nylon 100 Y/-1 buffer layer α1
kJl /wx”, optical phino < 7 Q OOkg
7m''.The following formula was used for calculation.

6 = EnAn e2 elongation strain, F: tension, E: Young's modulus, A: cross-sectional area, subscript n: indicates each member 0 Assuming that the allowable elongation strain of the original fiber is 12%, a metal-coated core with Kevlar longitudinally attached The wire can withstand up to a tension of approximately &5 kpf, which is about twice as high as a metal-coated core wire without Kevlar, and about 200 times higher than a conventional nylon core wire. There is no restriction on I# as long as the material for the shaku fibers has a heat resistance temperature higher than the melting point of the alloy and can be easily arranged in a wafer pattern, such as aramid fibers. In addition, polyethylene fibers, glass fibers, boron fibers, stainless steel fibers, etc. may also be used.In addition, in the i7 fiber core wire of the present invention, a plastic jacket may be applied around the metal coating layer. Examples of plastic jackets include polyethylene, polyvinyl chloride, Teflon, and nylon.

〔Example〕

Hereinafter, the present invention will be specifically explained using examples.
The invention is not limited to these examples.

Example 1 FIG. 1 is a cross-sectional view showing the structure of an example of the original fiber core wire of the present invention, in which 1 is the original fiber, 2 is the plastic buffer layer, 3F'i original fiber wire, and 6 is the aramid fiber. The fiber layer 7 is a metal coating layer.

Silicone resin was used as a plastic buffer layer around the single mode optical fiber with an outer diameter of α125.
■Aramid fibers (registered trademark: Kepler) T-of about 500 denier are attached vertically around the plastic coating layer, and then a low melting point alloy consisting of B1, PB%Sn, etc. is extruded and coated to form a metal coating layer. 7 and the outer diameter (L9-.By the way, B152%, Pb 51%, 8n1
The melting point of the low melting point alloy with the 7-chi blend is about 95°C.

Example 2 In this case, the aramid fibers play a role like a screw, which has the advantage of improving the adhesion between the low melting point alloy and the fibers in the extrusion direction. It goes without saying that the spirally wound fibrous body does not have to be one as shown in the figure, and may be a plurality of filaments or a cloth-like filament.

Embodiment 3 FIG. 6 is a sectional view showing the structure of another embodiment of the present invention, in which a plastic jacket 11 is provided around the metal-coated core wire shown in FIG. 1. It protects the metal coating layer 7 from external force and abrasion, has the function of electrical insulation, and is effective when used outdoors or when assembled with other core wires to form a cable.

Embodiment 4 In the above embodiments, explanations have been given using buffer layered strands containing only one original fiber, but the scope of the effects of the present invention is not limited to these, and The same applies to aggregates including original fibers. FIG. 7 is a cross-sectional view showing the structure of an example in which the present invention is applied to an aggregate including a plurality of original fibers, in which aramid fibers 6 are applied around the tape-shaped core wire 12, and metal It is covered with a coating layer. This provides convenience in transmission line sections that require all of a plurality of original fibers.

Embodiment 5 FIG. 8 is also a cross-sectional view showing the structure of an example in which the present invention is implemented for an assembly including a plurality of original fibers, in which aramid fibers are arranged around several optical fiber strands 3t concentrically assembled. , and is further coated with a metal coating layer 7.

〔Effect of the invention〕

As explained above, the metal-coated fiber core of the present invention has a coating layer made of fibers, such as an aramid fiber layer, and a low-melting-point alloy around the original fiber, so that it has a small diameter and It has excellent water pressure resistance, lateral pressure resistance, and tensile resistance, and can be used in a hydrogen atmosphere and can be manufactured in long lengths with low loss. It can be used in all kinds of harsh environments such as attached cable sections and piping inside buildings. Also,
When making a cable by assembling the core wires of the present invention, the core wires themselves have the above-mentioned mechanical properties, so the requirements for the cable structure are reduced, and the design aims for economical efficiency and environmental compatibility. It has the advantage of being easy.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of one embodiment of the original fiber core of the present invention, Fig. 2 is a schematic diagram of the method for producing a metal coating layer fiber, Fig. 3 is a core view of the optical fiber, and Fig. 10 is 11 is a cross-sectional view showing the structure of a conventional metal coated fiber core. FIG. 11 is a structural diagram of a conventional example in which a combined metal strip is used as a metal layer on the outside of the original fiber core. FIG. 12 is a cross-sectional view of the original fiber core. A structural diagram of a conventional example using a butt-formed tube as a metal layer on the outside, and FIG. 15 is a cross-sectional view showing the structure of a conventional metal coated fiber core wire. 1: original fiber, 2 niblastic buffer layer, 5 two optical fiber wires, 4 niblastic coating layer, 5: optical fiber core, 6: aramid fiber, 7: metal coating layer, 8: dice,
9: Two combined metal strips, 10: Butt-formed metal tube, 11: Niblastic jacket, 12: Tape-shaped core wire.

Claims (1)

[Claims] 1. At least one buffer layer is provided around the optical transmission glass fiber, the fibers are continuous in the longitudinal direction around the buffer layer, and the fibers are provided in a longitudinally continuous or spiral manner, and the melting point layer is further provided around the buffer layer. A metal-coated optical fiber core having a metal coating layer of a low-melting-point alloy with a temperature of 250° C. or less, characterized in that the heat-resistant temperature of the fiber is equal to or higher than the melting point of the low-melting-point alloy. line. 2. The metal-coated optical fiber core according to claim 1, which has a coating layer made of a plastic material around the metal coating layer. 3. Claim 1, wherein the fiber is an aramid fiber
The metal-coated optical fiber core according to item 1 or 2. 4. A plurality of optical fiber wires each having at least one layer of buffering layer applied around the glass fiber for optical transmission are assembled in a concentric circle or in parallel, and are continuous in the longitudinal direction in a vertical or spiral shape. The fiber applied to the surrounding area has a melting point of 250℃
A metal-coated optical fiber core wire having a metal coating layer of a low-melting point alloy as described below, wherein the allowable temperature limit of the fiber is equal to or higher than the melting point of the low-melting point alloy. 5. The metal-coated optical fiber core according to claim 4, which has a coating layer made of a plastic material around the metal coating layer. 6. Claim 4, wherein the fiber is an aramid fiber
The metal-coated optical fiber core according to item 5 or item 5.