JPS59164652A - Production of optical fiber covered by metal - Google Patents

Abstract

PURPOSE:To increase ductility of covering metallic film, to improve the strength of optical fiber covered by a metallic film, and to reduce the dispersion of quality of the product by performing heat-treatment after a bare optical fiber is coated with a metal. CONSTITUTION:A bare optical fiber 3 produced by drawing of a heat-melted base material for glass 1 is conducted to a metal coating device 4 where it is coated with a metal. The metal coated optical fiber 5 is wound by a winding drum 7 installed to the inside of a slow cooling device 6 for maintaining the fiber 5 at a fixed temp. and the fiber 5 is cooled slowly. By this treatment, the strength of the fiber 5 is improved and the dispersion of the quality of the product is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal coated optical fiber with excellent strength.

Metal-coated optical fiber, which is a bare optical fiber made of silica glass whose outer circumferential surface is coated with metal, has the following advantages: the metal coating has excellent heat resistance, and the metal gate prevents water permeation. In order to manufacture optical fibers that have excellent heat resistance, moisture resistance, and long-term reliability, and can be used even in high-temperature, high-humidity environments, for example, after melt-spinning bare optical fibers from a glass-free material, A method is known in which the material is immediately introduced into a metal coating device using the Ditsuno method or the like, coated with metal to a predetermined thickness, cooled at room temperature, and wound up.

According to the method described above, the bare optical fiber is coated with metal immediately after melt spinning, so that the surface of the bare optical fiber can be maintained in a state where there are almost no minute scratches (flows). Since the bare optical fiber in this state has almost no flow, it exhibits tensile strength and elongation close to the theoretical values, with an elongation rate of nearly 30 inches. However, since the metal coating coated on such a stretchable bare optical fiber is rapidly cooled from a few hundred dust Celsius to room temperature, a strong thermal shock acts on the metal coating, which damages the internal structure of the metal coating. Internal stress occurs when the defect occurs. Furthermore, since the metal coating is rapidly cooled, the metal coating is in a quenched state, and therefore the structure of the metal coating is fixed in an unstable state and becomes hardened and has poor ductility.

1, ;) Therefore, the ductility of the metal coating and the optical fiber probe leads to minute scratches on the surface of the bare eyeglass wire, and these scratches reduce the strength of the metal coated optical fiber.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a method for threading a metal-coated fiber with excellent strength.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of an apparatus suitable for the method of manufacturing a metal-coated optical fiber of the present invention, in which numeral 1 indicates a glass base material. The glass base material 1 is heated and melted in a carbon resistance furnace 2 and spun. The spun bare optical fiber 3 is immediately guided to a metal coating device 4 using the Ditsuno method, chemical vapor deposition method, or sputtering method, and is coated with metal to form a metal coated optical fiber 5. The metal-coated optical fiber 5 is wound around a winding drum 7 installed inside an annealing device 6 kept at a predetermined temperature so as not to be rapidly cooled. The speed of spinning the original bare fiber is 10 m/min to 1
Since the speed is as high as 00 m, it can be considered that the metal-coated optical fiber 5 is accommodated in the mirror device 6 immediately after being coated with metal. The slow cooling device 6;)s H consists of a main body 8 in which a rolled salt drum 7 is housed, and a hot air device 9 for blowing air through the heated animal, and a metal-coated optical fiber 5 is introduced into the main body 8. A hot air device 9 is provided with an inlet 8a and an air outlet 8b through which heated gas is blown.
The inside of the main body 8 is maintained at a predetermined temperature by heated gas blown from the main body 8.

The temperature at which the metal-coated optical fiber 5 is slowly cooled varies depending on the metal to be coated, the coating method, the thickness of the metal coating, and the desired properties, but is generally 1/3 to 2/2 of the melting point of the metal.
3 or so is preferable, for example, for At, 210 to 440°C
For Sn, the temperature is preferably about 70 to 160°C. Although the time for slow cooling also varies depending on various conditions, it is necessary to leave the winding drum 7 in the slow cooling device 6 for a certain period of time after the final winding of the metal-coated optical fiber 5 is completed.

In this way, the metal-coated optical fiber 5 is immediately housed in the annealing device 6 and kept at a predetermined temperature for a predetermined period of time to be annealed.
The metal coating is subjected to less thermal shock and is in an annealed state, so there are no internal defects and no external residual stress.
Furthermore, it becomes soft and ductile due to its stable structure. The effect of this slow cooling is that the difference in elongation between castings and annealed materials of the same metal is 1. The heat-retaining furnace 10 is provided with a heat-retaining furnace 10.(5) The heat-retaining furnace 10 is heated by an internal electric resistance ill, and the internal temperature is varied from a temperature slightly lower than the melting point of the coated metal to a temperature slightly lower than the melting point of the coated metal. Temperature range m1 of about 1/2 of, for example, At650~32
The metal-coated optical fiber 5 is maintained between the metal-coated device 4 and the slow cooling device 6.
This is to prevent the water from cooling down rapidly. It is thought that the effect of the annealing device 6 can be obtained by using this insulating furnace 10, but since the optical fiber is spun at high speed, the insulating furnace 10 becomes long, which is not practical. It is preferable to provide an annealing device 6 also at the drum 7 portion. It is more preferable to create a temperature gradient in the heat-retaining furnace 10 and lead it to the slow cooling device.

The metal coating layer of the metal coated optical fiber 5 manufactured by being slowly cooled after being coated with metal in this way has a high ductility, so when the metal coated optical fiber is stretched, the metal coating layer does not absorb light. It can be stretched as the bare fiber wire is stretched.

(6) Use something of excellent strength. ! , there are fewer residual stresses and defects in the metal coating, and therefore stable strength can be maintained.

Note that although the method of heating the annealing device 6 and the insulating furnace 10 in the manufacturing apparatus shown in FIGS. 1 and 2 include a method using heated gas and a method using an electric resistance wire 11, the present invention is not limited to these methods. Any other method may be used as long as the same effect can be obtained without causing any heat loss. For example, a method using infrared rays, far infrared rays, etc., a method using induction heating, etc. may be used. Further, the slow cooling device 6 may heat the winding drum from inside the winding drum instead of heating the winding drum from the outside.

Next, the method for manufacturing a metal-coated optical fiber of the present invention will be explained in detail with reference to Examples.

[Example 1] Glass m material 1 made of quartz glass was spun at 40 m/min using the apparatus shown in Fig. 1, and the core diameter was Sn.
After coating the winding drum 7 in the slow cooling device 6,
The temperature inside the slow cooling device 6 was gradually lowered to room temperature 1, and then the sample was taken out.

An Sn metal-coated optical fiber (A) produced by the above production method is compared with a method (conventional method) that differs from the above production method only in that no heat treatment is performed using the annealing device 6. A tensile strength test was conducted with a Sn metal-coated optical fiber (n) manufactured by a corresponding method), and the probability of breakage was evaluated using the Winol distribution shown in FIG. The conditions for the tensile strength test were a length of 300 mm, a tensile speed of 30 mm/min, and a number of samples of 50.

As can be seen from FIG. 3, the Sn metal-coated optical fiber (G) manufactured by the method of manufacturing a metal-coated optical fiber of the present invention has a minimum strength of 8.5 kg.
This is significantly improved compared to 6.0 kfl of Sn metal-coated optical fiber...Φ). Further, Sn metal-coated optical fiber [Example 2] The bare fiber wire 3 was coated with A7 having a purity of 99.999% to a thickness of 2 μm by sputtering. At this time, the reaction temperature of the metal coating device 4 was 600°C. The heat retention furnace 10 following the metal coating device 4 had a furnace length of 6 m, and the temperature inside the furnace was 350° C. using infrared rays as a heating source. The temperature inside the annealing device 6 was set at 250° C., and the metal-coated optical fiber was kept warm in the furnace for one hour even after winding was completed.

At metal-coated optical fiber manufactured by the following method...
・C) and as a comparative example, the above manufacturing method and insulating furnace (9
) 10 and an At metal-coated optical fiber manufactured by a method (corresponding to the conventional method) that differs only in that it does not use an annealing device and 6...
When the tensile strength was tested at 0 mm/min, the average tensile strength of each of the At-coated optical fibers (C
) 6. Okg, At metal-coated optical fiber by conventional method 77 As explained above, the metal-coated optical fiber of the present invention has increased ductility, and therefore, the metal-coated optical fiber produced by this manufacturing method has excellent strength and is free from product variation. It becomes less.

[Brief explanation of drawings]

FIGS. 1 and 2 are both schematic configuration diagrams showing an example (10) of a manufacturing apparatus suitable for the method of manufacturing a metal-coated optical fiber of the present invention, and FIG. 3 is a method of manufacturing a metal-coated optical fiber of the present invention. 1 is a graph showing the breakage probability of a metal-coated optical fiber manufactured by a Weibull distribution. In the figure, 3... Bare optical fiber, 5... Metal coated optical fiber, 6... Annealing device. Patent applicant Makoto Ishizaka, Director of the Institute of Industrial Science and Technology −

Claims (3)

[Claims] (1) A method for manufacturing a metal-coated optical fiber, which comprises applying a metal coating to a bare optical fiber and then slowly cooling the metal coating. (2) The method for manufacturing a metal-coated optical fiber according to claim 1, characterized in that the metal coating is slowly cooled at least at a position where the metal-coated optical fiber is wound. (3) The method for manufacturing a metal-coated optical fiber according to claim 1, wherein slow cooling is performed immediately after coating the metal and at a position where the metal-coated optical fiber is wound.