JP2007272009A - Heat-resistant optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant optical fiber cable in which an optical fiber can be sufficiently functioned even under a high temperature. <P>SOLUTION: In the optical fiber cable formed by applying a heat-resistant coat layer to the outer circumferential surface of an optical fiber core 2 to form a metallic fiber and inserting a protecting metallic tube 4 into the optical fiber 1, the metallic tube is formed by the butt welding of metallic tapes composed of alloy containing ≥45 wt.% Ni, ≥15 wt.% Cr and ≤1 wt.% C, and inertia gas 5 is sealed into the metallic tube. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-resistant optical fiber cable.

  Optical fiber cables used for communications and temperature sensor applications in a high temperature environment are required to have heat resistance so that the characteristics of the optical fiber do not deteriorate even in a high temperature environment.

  As an optical fiber for heat resistance, an optical fiber in which an optical fiber core wire is coated with a heat resistant resin such as polyimide or Teflon (registered trademark) is known, but the heat resistance is limited to about 200 ° C.

For example, Patent Document 1 discloses an optical fiber cable in which a metal heat-resistant layer is formed on the outer periphery of an optical fiber core and the metal-coated optical fiber is inserted into a protective metal tube. Has been.
JP 2000-131570 A

  However, even in an optical fiber cable coated with a metal heat-resistant layer disclosed in Patent Document 1, the heat-resistant layer comes into contact with the air in the metal tube in an extremely high temperature environment exceeding 400 ° C. Since the heat resistance is lowered and the loss and strength of the optical fiber easily deteriorate, there is a demand for an optical fiber cable that does not deteriorate the characteristics of the optical fiber even under such an extremely high temperature. When stainless steel is used as the material of the metal tube, the corrosion resistance is poor at a high temperature exceeding 400 ° C., and corrosion progresses to generate small holes and deteriorate the strength.

  In view of such circumstances, the present invention provides heat resistance to an optical fiber for a long period of time without being oxidized or corroded even at an ultra-high temperature. It is an object of the present invention to provide a heat-resistant optical fiber cable that can be maintained and can secure the manufacturability of a metal tube obtained by butt welding of a metal tape.

  The heat-resistant optical fiber cable according to the present invention is formed by forming a heat-resistant optical fiber by applying a heat-resistant coating layer to the outer peripheral surface of the optical fiber core, and inserting the optical fiber into a protective metal tube.

  In such a heat-resistant optical fiber cable, according to the present invention, the metal tube is made by butt-welding a metal tape of an alloy containing Ni at 45% by weight or more, Cr at 15% by weight or more, and C at 1% by weight or less. And an inert gas is sealed in the metal tube.

  In such a heat-resistant optical fiber cable of the present invention, in addition to the heat-resistant coating layer protecting the optical fiber core wire by its heat-resistant characteristics, the metal tube into which this optical fiber is inserted also has heat resistance, Protect optical fiber from high temperature atmosphere.

  At high temperatures, the metal tube can be improved in corrosion resistance by increasing the Ni content. Further, the oxidation resistance is improved by increasing the Cr content. On the other hand, if the content of C is large, thermal tube cracking occurs during welding.

  If Cr is 15% by weight or more, sufficient oxidation resistance can be secured. Therefore, if the Ni content is increased as much as possible, the corrosion resistance can be improved. The metal tube contains 45% by weight or more of Ni to enhance the corrosion resistance at high temperature, and contains 15% by weight or more of Cr to improve the oxidation resistance at high temperature. Further, since the metal tape forming the metal pipe has a C content of 1% by weight or less, the weldability is good, and the ease of manufacturing the metal pipe by butt welding is kept good.

  Furthermore, in the present invention, an inert gas is sealed in the metal tube, so that oxidation in the heat-resistant coating layer and the inner surface of the metal tube is prevented, and as a result, heat resistance is maintained. As the inert gas, argon gas, nitrogen gas, helium gas and the like are suitable.

  In the present invention, the heat-resistant coating layer can be a metal coating layer. As the metal for this purpose, copper, aluminum, titanium, gold, etc., or an alloy containing one of these can be used.

  In the present invention, as described above, a heat-resistant coating layer is applied to the optical fiber core, and a metal tape of an alloy of Ni ≧ 45 wt%, Cr ≧ 15 wt%, and C ≦ 1 wt% is butt welded. However, since the optical fiber is inserted into the metal tube and the inert gas is sealed, not only can the heat resistance of the optical fiber core wire be ensured by the heat-resistant coating layer, but it is also resistant to ultra high temperatures. Metal pipe containing Ni having high corrosivity and Cr having high oxidation resistance and the presence of inert gas in the metal pipe prevent corrosion and oxidation of the metal pipe. Overall heat resistance can be secured over a long period of time. As a result, the performance of the optical fiber cable can be maintained as it is even under an ultra-high temperature. Moreover, the metal tape is rolled in the width direction and butt-welded to form a metal tube, so that it is easy to obtain a long metal tube. Since the metal tape is C ≦ 1% by weight, the weldability is good. Manufacture is easy by inserting an optical fiber into the cable.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 of the accompanying drawings.

  FIG. 1 is a sectional view perpendicular to the axial direction of a heat-resistant optical fiber cable extending long in the direction perpendicular to the paper surface.

  In FIG. 1, an optical fiber core wire 2 is provided with a heat-resistant coating layer 3 to form an optical fiber 1. As a material of the heat-resistant coating layer 3, for example, metal can be used, and copper, aluminum, titanium, further gold, or an alloy containing one of them can be used.

  The optical fiber 1 having the heat-resistant coating layer 3 is inserted into a metal tube 4 having an inner diameter sufficiently larger than the outer diameter. The metal tube 4 is formed by rolling a metal tape containing 45% by weight or more of Ni, 15% by weight or more of Cr, and 1% by weight or less of C, and butting them at the side edges. .

  Further, an inert gas 5 is sealed in the metal tube 4. As this inert gas, for example, argon gas, nitrogen gas, helium gas or the like is appropriately selected. Of course, both ends of the metal tube 4 are sealed so as not to leak inert gas.

  In such an optical fiber cable of this embodiment, since the optical fiber 1 is provided with the heat-resistant coating layer 3, the optical fiber 1 is protected by heat alone, but is inserted into the metal tube 4. Is also protected by.

  This metal tube 4 contains 45% by weight or more of Ni, so that the corrosion resistance is enhanced at a high temperature. Since Cr contains 15% by weight or more, the oxidation resistance at a high temperature is increased, and Deterioration is prevented.

  Further, since the metal tape forming the metal tube 4 has C of 1% by weight or less, the weldability is good and the metal tube 4 can be easily manufactured by butt welding the metal tape.

  Further, since the inert gas is sealed in the metal tube 4, oxidation on the inner surface of the heat-resistant coating layer 3 and the metal tube 4 of the optical fiber 1 is prevented, and the functions of the heat-resistant coating layer 3 and the metal tube 4 are prevented. The heat resistance of the optical fiber 1 is sufficiently maintained as it is maintained as it is.

  An optical fiber cable in which an optical fiber coated with a heat resistant coating of a copper alloy of an optical fiber core wire was inserted into a metal tube made of an Inconel (registered trademark) alloy metal tape was evaluated. The inconel alloy was evaluated for various types, and all of them were Ni ≧ 45 wt%, Cr ≧ 15 wt%, and C ≦ 1 wt%. Inconel 600 in particular has Ni = 76% by weight, Cr = 15%, and C = 0.2%, and has high corrosion resistance.

  A sample in which a metal tube was filled with an inert gas (argon gas) and a sample in which the metal tube was not filled with an inert gas (normal air in the metal tube) were prepared and held in a constant temperature bath at 450 ° C. for 24 hours. Later, the tensile strength (breaking excess) of the optical fibers in the metal tubes was compared.

  In the sample not filled with argon gas, the tensile strength decreased to an average of about 22% of the original strength of the optical fiber. On the other hand, no decrease in tensile strength was observed in the sample filled with argon gas.

  Further, the temperature characteristics were evaluated while being kept in a constant temperature bath at 450 ° C. for 24 hours. In the sample not filled with argon gas, the light loss increased greatly, but in the sample filled with argon gas, no significant increase in light loss was observed.

  As described above, it was confirmed that filling the inert gas into the metal tube can suppress the optical loss and the deterioration of the optical fiber strength due to the oxidative deterioration of the optical fiber even at an extremely high temperature exceeding 400 ° C. .

It is sectional drawing of the optical fiber cable as one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Optical fiber core wire 3 Heat-resistant coating layer 4 Metal pipe 5 Inert gas

Claims (2)

  In a heat-resistant optical fiber cable in which a heat-resistant optical fiber is formed by applying a heat-resistant coating layer to the outer peripheral surface of the optical fiber core, and this optical fiber is inserted into a protective metal tube, the metal tube is made of 45 wt% Ni, Cr Is produced by butt welding a metal tape of an alloy containing 15 wt% or more of C and 1 wt% or less of C, and an inert gas is enclosed in the metal tube Fiber cable. The heat resistant optical fiber cable according to claim 1, wherein the heat resistant coating layer is a metal coating layer.

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