JPH04360110A - Optical fiber blank material and production thereof - Google Patents

Abstract

PURPOSE:To produce the optical fiber blank material having excellent heat resistance and flexibility by functioning a metallic tube fitted to a coated optical fiber as a metallic film layer. CONSTITUTION:After the entire part of the coated optical fiber 4 obtd. by coating the surface of an optical fiber 2 with the metallic film 3 is fitted into the slender metallic tube 5, this metallic tube 5 is passed through a die and is thereby reduced in diameter. The entire part of the coated optical fiber 4 obtd. by forming a soft wax film 6 on the metal coated optical fiber is fitted into the slender metallic tube 5 and thereafter this metallic tube 5 is diametrally worked and the entire part is subjected to a heating treatment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber material having excellent heat resistance and flexibility due to fitted metal tubes functioning as a relatively thick metal coating layer, and a method for manufacturing the same.

0002

2. Description of the Related Art Optical fibers are required to be heat resistant for use in optical overhead ground wires, such as for being incorporated into the ground wire of high-voltage power transmission lines, or for ignition in thyristors. Additionally, if it can withstand higher temperatures than the current one, it is expected to be used for wiring and measurement around high-temperature reactors. Conventional optical fibers are coated with UV resin or nylon resin for surface protection, but this resin coating cannot sufficiently increase the heat resistance of the optical fiber cable.

[0003]Therefore, attempts have been made to further increase the heat resistance and mechanical strength of optical fiber cores by protecting the optical fiber surface with a metal coating. To coat an optical fiber with a metal film, a molten preform is drawn and molten metal is applied at the same time, or a metal film is formed by plating or vacuum deposition after drawing.

0004

[Problems to be Solved by the Invention] When coating a metal film using a plating method or a vacuum evaporation method, the thicker the metal film is, the better it is for heat resistance and fire resistance. If the metal film is made thicker, the growth rate of plating, etc. is slow, so it takes a lot of time to form the metal film. On the other hand, if the metal coating becomes too thick, the flexibility of the optical fiber core will be relatively reduced, making installation work difficult.

In this optical fiber, the thickness of the metal coating is a predetermined value (1 to 5 μm for copper, 1 to 2 μm for nickel).
μm) or less, the coated metal will oxidize in an oxidizing atmosphere and light The mechanical strength of the fiber core deteriorates and it breaks.

[0006] When molten metal is applied at the same time as the molten preform is drawn, the metal coating is limited to one with a low melting point. The metal coated optical fiber thus obtained has the problem that the thicker the metal coating, the more likely the eccentricity of the optical fiber increases, making it difficult to control the thickness of the metal coating.

[0007]Furthermore, when an optical fiber is inserted into the tissue of an animal or plant through its epidermis to measure the internal tissue of the animal or plant, the optical fiber is placed in an elongated metal capillary and fixed by adhesive. In this adhesive fixing method, the optical fiber tends to shift from the center in the metal capillary depending on the size of the clearance, and it is difficult to fix the optical fiber in the capillary.

[0008] There is a limit to the diameter reduction of metal capillaries by tube manufacturing technology. Therefore, if the diameter of the optical fiber is carefully reduced after insertion, even if the diameter can be reduced to a length of several tens of centimeters as in this case, there is a risk that the optical fiber may break during processing. The resulting capillary has poor flexibility due to the weak inserted optical fiber.

The present invention was proposed in order to improve the above-mentioned problems regarding the heat resistance of optical fibers, and an object of the present invention is to provide an optical fiber material that has excellent heat resistance and flexibility as well as high airtightness. It is an object. Another object of the present invention is to provide a method for manufacturing an optical fiber material with excellent heat resistance and flexibility by fitting metal tubes and then reducing the diameter.

0010

[Means for Solving the Problems] In order to achieve the above object, an optical fiber material 1 according to the present invention has an optical fiber core 4 having a metal coating 3 coated on an optical fiber 2, as shown in FIG. and an elongated metal tube 5 which is fitted into the optical fiber. Optical fiber material 1 shown in Figure 3
Now, a bonding soft solder layer 6 is formed between the inner circumferential surface of the metal tube 5 after diameter reduction processing and the outer circumferential surface of the metal coating 3 of the optical fiber core 4.
is intervening.

The metal film 3 to be coated on the optical fiber 2 may be coated directly onto the optical fiber 2, but usually the optical fiber 2 is coated with a carbon film (not shown) and then electroless plating is applied. , first formed to a thickness of several micrometers or less by vacuum evaporation, sputtering, ion plating, etc., and then further formed to a specified thickness by electroplating, and the material may be copper, nickel, aluminum, silver, gold, etc. It is.

The inner diameter of the metal tube 5 must be as small as possible within a range that allows the optical fiber core 4 to be inserted therein, and it must be made of metal that can be reduced in diameter. If the soft solder layer 6 is to be formed on the optical fiber core 4, the material of the metal tube 5 may be selected from copper, tin, nickel, silver, gold, etc., which can be bonded to the soft solder layer. Even if the length of the metal tube 5 is more than ten meters, it can be used.

In the method of the present invention, the optical fiber 2 is coated with a metal film 3, the entire optical fiber core 4 obtained is inserted into a long and thin metal tube 5, and then the metal tube 5 is passed through a die 7 (see FIG. 2) to reduce the diameter. In the optical fiber core wire 4, it is preferable to form a soft solder layer 6 on the metal coating 3 before inserting it into the metal tube 5, and if the tube is diameter-reduced and then heat-treated as a whole, the overall airtightness is increased. .

The soft solder layer 6 (FIG. 3) is generally made of a tin-lead alloy called solder, but bismuth, indium, or the like may be added to lower the melting point. Examples of the soft solder layer 6 include non-toxic tin-antimony alloys, tin-silver alloys, and high-temperature lead-silver alloys, and if the melting point is considerably lower than the glass transition point, it is usually classified as hard solder. You can also use

[0015]

[Operation] In the method of the present invention, the optical fiber core 4 is inserted into the metal tube 5 and subjected to diameter reduction processing, so that the inner peripheral surface of the tube comes into close contact with the metal coating 3 of the optical fiber core 4. The optical fiber material thus obtained has high heat resistance and flexibility because the metal tube 5 substantially functions as a thick metal coating layer of the optical fiber 2. In addition, in the method of the present invention, if the soft solder layer 6 is formed on the metal coating 3 of the optical fiber core 4, the entire optical fiber material will be air-tight after the metal tube 5 is diameter-reduced and the whole is heat-treated. becomes more sexual.

Unlike a metal wire, the quartz-based optical fiber itself cannot be drawn for diameter reduction unless it is in a molten state. This will be limited to one time until it almost matches . The inner diameter of the metal tube 5 must be as small as possible to allow insertion of the optical fiber coated wire 4, and if the clearance between the inner diameter of the tube and the outer diameter of the optical fiber coated wire 4 is large, the optical fiber coated wire This causes eccentricity of the metal tube 4, and the area reduction rate of the metal tube 5 increases, making diameter reduction processing difficult.

[0017]

EXAMPLES Next, the present invention will be explained based on examples. Example 1 When a single mode optical fiber (cladding diameter 125 μm) with a core diameter of 10 μm is thinly coated with a carbon film and a base metal film, and then coated with a 5 μm thick nickel film 3, an optical fiber core 4 is formed. The outer diameter of is 135μ
m, and its total length is 6 m. This optical fiber core wire 4 has an inner diameter of 150 μm, an outer diameter of 380 μm, and a length of 5 m (
After inserting the wire into the copper tube 5 (excluding the lead portion), the entire wire is drawn through a die 7 (FIG. 2) having an inner diameter of 350 μm to reduce its diameter.

After the diameter reduction drawing, 16 cm of the optical fiber core 4 remains outside the copper tube 5 . That is, 5 m and 84 cm of the optical fiber core wire 4 was secondarily coated with the copper tube 5. At this time, the area reduction rate of the copper tube 5 was 14.4%, and the space reduction rate of the space inside the tube was 19.
1%, and the optical fiber core 4 is actually inserted into the inner space of the tube.

After polishing the end face of the optical fiber material after diameter reduction drawing, the presence or absence of breakage is examined by entering light into the optical fiber 2 using an LD beam. As a result, it becomes clear that there is no breakage of the optical fiber 2 in this optical fiber material.

Example 2 Using the optical fiber core 4 in Example 1, the fiber core was further immersed in a molten solder bath of Sn60:Pb40 and then pulled out to form a 1 μm thick solder layer on the nickel film 3. 6 (outer diameter 137 μm) is prepared. Hereinafter, the same process as in Example 1 is carried out.

After the diameter reduction drawing, 13 cm of the optical fiber core 4 remains outside the copper tube 5 . That is, 5 m and 87 cm of the optical fiber core wire 4 was secondarily coated with the copper tube 5. At this time, the area reduction rate of the copper tube 5 was 14.9%, and the space reduction rate of the space inside the tube was 16.
It is 4%.

[0022] The optical fiber material after diameter reduction drawing is 230
After being left in a constant temperature bath at .degree. C. for 5 minutes, it is taken out, the end face of the obtained optical fiber material 1 is polished, and then light is incident on the optical fiber 2 using an LD beam to check for breakage. As a result, it becomes clear that there is no breakage of the optical fiber 2 in the optical fiber material 1.

Further, when the end face of the optical fiber material 1 was observed under a microscope, it was found that the interface between the nickel coating 3 of the optical fiber core 4 and the copper tube 5 was sufficiently bonded.

[0024]

[Effects of the Invention] In the method of the present invention, by inserting the optical fiber core into a metal tube and reducing its diameter, the optical fiber material coated with the metal tube, which functions as a substantially thick metal coating layer, can be rapidly produced. can be manufactured. If the method of the present invention is used to reduce the diameter of an optical fiber after insertion, it is possible to reduce the diameter of an optical fiber that is several meters long, and the optical fiber will not break during processing. It also has excellent flexibility.

The optical fiber material of the present invention has sufficient heat resistance and mechanical strength because the metal tube is sufficiently thick compared to the case where a metal film is coated by a plating method, etc., and is suitable as a heat-resistant and fire-resistant material. It is. The metal tube of this optical fiber material hardly oxidizes even under the severe conditions of 840℃ (fire resistance curve) in the fire and heat resistance test stipulated by Fire and Disaster Management Agency Notification No. 10, and the mechanical strength of the optical fiber deteriorates. No breakage occurs.

Even if the metal tube used in the present invention is thick enough to correspond to a thick metal film layer formed by electroplating, the time required for fitting and fixing is extremely short, and the fitting and fixing improves the flexibility of the optical fiber. The installation work is easy because there is almost no deterioration. This metal tube is not limited to a material with a low melting point as is the case when molten metal is applied at the same time as drawing a molten preform, and the eccentricity of the optical fiber is small even with a thick wall. It can be selected almost arbitrarily.

Furthermore, if the optical fiber material of the present invention is used when measuring the internal tissues of animals and plants by inserting the optical fiber into the tissues of animals and plants through the epidermis, it is possible to make the optical fibers sufficiently thin, and the optical fiber can be The sealing performance between the fiber coated wire and the metal tube is high and airtight, and the optical fiber coated wire does not shift from the center due to clearance.

[Brief explanation of the drawing]

FIG. 1 is an enlarged vertical cross-sectional view showing an optical fiber core and a metal tube used in the method of the present invention.

FIG. 2 is a longitudinal sectional view showing an enlarged diameter reduction step in the method of the present invention.

FIG. 3 is an enlarged cross-sectional view showing an optical fiber material according to the present invention.

[Explanation of symbols]

1 Optical fiber material 2 Optical fiber 3 Metal coating 4 Optical fiber core 5 Metal tube 6 Bonding soft solder layer

Claims (3)

[Claims] Claim 1: Consisting of an optical fiber coated with a metal film on the optical fiber, and a long and thin metal tube that is fitted with the optical fiber, the inner peripheral surface of the metal tube after diameter reduction processing and the optical An optical fiber material in which a soft solder layer is interposed between the outer peripheral surface of the metal coating of the fiber core. [Claim 2] Coating a metal film on the optical fiber,
The entire optical fiber thus obtained is inserted into a long and thin metal tube, and this metal tube is passed through a die to reduce its diameter, thereby bringing the inner peripheral surface of the metal tube into close contact with the metal coating of the optical fiber. Method of manufacturing fiber material. [Claim 3] Coating a metal film on the optical fiber,
Next, after forming a soft brazing film on the metal film, the entire optical fiber obtained is inserted into a long and thin metal tube, the metal tube is diameter-reduced, and the whole is heat-treated. A method of manufacturing an optical fiber material in which the metal coating of an optical fiber core wire and the inner peripheral surface of a metal tube are bonded and sealed using a soft solder layer.