JPH02166410A - Hermetically coated optical fiber - Google Patents

Abstract

PURPOSE:To obtain the optical fiber which decreases infiltration of H2 and moisture and allows easy soldering by providing a carbon coating layer right on a glass fiber and providing a metallic coating on the outer side thereof. CONSTITUTION:A carbon coat 30 and a metallic coat 32 are successively provided on the outer side of the glass fiber 14. The glass fiber is completely coated with the carbon film, by which the infiltration of the moisture and H2 particles into the fiber surface and the inside is prevented with nearly the perfect accuracy. In addition, the carbon is extremely thin and the metallic film to be formed thereon is suppressed to about several mum at the most. The hermetic coating which is not adversely affected by the H2, etc., and allows easy soldering by the metallic coating is obtd. in this way.

Description

[Detailed description of the invention] <Field of industrial application> This invention has high strength, water resistance, and hydrogen resistance5. The present invention relates to a hermetic coated optical fiber that is suitable for use under special environments and is characterized by heat resistance.

<Prior Art><Problems to be Solved by the Invention> Optical fibers are known in which a glass fiber for light transmission is coated with a metal, thereby making it possible to be soldered. An example of such a conventional optical fiber is a straight 1.4 quartz optical fiber. For example, a quartz-based optical fiber is passed through a tank L7 filled with molten aluminum and drawn through a die Z7 to produce an optical fiber whose surface is coated with aluminum.

The problem with such aluminum-coated optical fibers is (
Since the melting point of No. 11 aluminum is high, a reaction occurs at the interface between glass and aluminum, reducing the mechanical strength of the fiber. (2) Products manufactured by applying aluminum by dipping tend to have a thick coating of aluminum, and large shrinkage strains occur when the aluminum cools and solidifies from a molten state to room temperature. , the fiber is compressed with very large forces.

Therefore, if even the slightest non-uniform stress occurs, random bending occurs in the longitudinal direction of the fiber, which inevitably increases the transmission loss of the optical fiber due to the bending.

Metal is sputtered or vapor deposited on the fiber surface.
I! In the case of overturning, the thickness of the metal coating can be made thinner, but the manufacturing process is carried out under reduced pressure, which causes major damage to the equipment. In order to reduce the pressure only in the evaporation area and the evaporation area, differential pumping units are required on both sides of the core area, resulting in a large loss of equipment.

Although it is not a metal, there is a technology to coat a carbon blank directly on the fiber, and the common method is to densely form pyrolytic graphite on the fiber surface, forming a nice and dense layer. If this is done, the intrusion of moisture, H, and molecules into the fiber surface and interior will be completely eliminated for several decades, so a very stable fiber can be obtained. However, carbon black has low hardness and is susceptible to scratches, so scratches are inevitable, and
The metal-coated fiber described above is also used as a fiber with little water penetration, but this carbon-coated fiber cannot be soldered and is not suitable for processing the terminal portion of an optical fiber communication system.

Means for Solving the Problems> The present invention has been made to solve the above problems, and
The outline is as follows.

A carbon coating layer (
A metal coating layer is provided on the outside of the film.

To manufacture an optical fiber with the above structure, for example, a dense carbon film is first formed directly on the glass fiber, and a metal film is formed on it by electroplating or electroless plating, utilizing the conductivity of this carbon film. This is done by

<Function> Since the optical fiber of the present invention has the above-described structure, the glass fiber is completely coated with the carbon film, so that moisture and six molecules can penetrate into the fiber surface and inside with near-perfect precision. In addition, the carbon film is extremely thin, and the metal film applied on top of it can be kept to a few micrometers at most (however, depending on the use of the fiber, it may be coated thicker). Unlike the conventional dipping method, the film does not become unnecessarily thick, and unnecessary increase in loss can be avoided. Furthermore, if you choose a metal that is easy to solder, it is possible to connect the optical fiber and various optical fiber communication component devices, such as the connection part with the light source and the connection part with the light receiver, with complete airtightness. Become.

<Embodiment> FIGS. 1 and 2 are schematic diagrams of an apparatus used in the present invention, and the configuration thereof will first be explained.

FIG. 1 shows an apparatus that continuously manufactures glass fiber and coats it with carbon. A fiber preform (base material) 10 is spun through a heating furnace 12 to form a bare fiber 14, which is then led to a gas decomposition furnace 16 and coated on the surface. A carbon coated fiber 1B encoded with carbon is manufactured. 20 is a carbon-containing gas supply port of the gas cracking furnace, 22 is an exhaust port of the gas cracking furnace, and 24 is a winding device for the carbon-coated fiber 18.

FIG. 2 shows an example of means for applying metal coating (copper plating) on a carbon-coated optical fiber.
An electrode 26 is used, and a plating electrolyte 28 is put into the electrode 26 to perform electroplating.

FIG. 3 is a cross-sectional view showing the structure of the optical fiber of the present invention obtained in this way, in which a carbon coat 30 is coated on the outside of the glass fiber 14. It has a structure in which metal coats 32 are sequentially provided.

To describe an example of manufacturing a hermetic coated optical fiber of the present invention, a carbon coated optical fiber was manufactured as shown in FIG. 1 under the following conditions.

Fiber base material diameter 25 φ Fiber drawing speed 20m 1 minute Fiber outer diameter 125μm Carbon generating raw materials C, F.

Heat Source: Electric Furnace Carbon Coating Thickness: 900 people The obtained carbon coated fiber was plated using the apparatus shown in FIG.

The conditions are as follows.

Electrolyte cyan bath, pyrophosphate bath, etc., current density
The shape of the electrolyte bath can be, for example, cylindrical so that the fiber can be plated while running, or the bath can be shaped like a shallow bath and the fiber can be gently curved for plating.

Plating may be affected by the surface material of the carbon coat, but this effect can be avoided by increasing the thickness of the plating layer.

Also, since the voltage is supplied from one end of the carbon-coated fiber, it is affected by the current density, so for example, as shown in Figure 2, the shape of the anode is made tapered to equalize the effect of the current density in the length direction of the fiber. can do.

In addition, metals suitable for plating in the present invention include:
Cd, Cr, An! l Agt Ni, Ifi
l Zllll ALII Sn.

Re, Mo, Sb, Bi, etc.

As shown in FIG. 3, the fiber obtained according to the present invention can be soldered very easily when the package of the light emitting and light receiving element is made hermetic and light is extracted through the fiber.

In the figure, 34 is a metal-coated optical fiber that is hermetically connected to an optical semiconductor element 38 in an optical semiconductor package 36.

40 is a lead wire of the optical semiconductor element 38, and the insertion opening of the package is sealed with a sealing material 42.

The insertion opening of the package for the metal-coated optical fiber 34 is welded with solder 44.

In addition, the distortion of the optical fiber due to the stress of metal electrodeposition causes so-called "
It is conceivable that this may cause "microbend loss" and scattering loss of light traveling through the fiber, but in such applications, the length is short and the loss is O, ldB/si.
It can be placed in the following order.

<Effects of the Invention> According to the present invention, it is possible to provide a hermetic coat using a carbon coat that has complete moisture that cannot be obtained with a metal coat alone, without being affected by adverse effects such as can.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a carbon coating process, FIG. 2 is an explanatory diagram of a metal coating process, and FIG. 3 is a sectional view showing an example of a hermetic coated optical fiber according to the present invention.
FIG. 4 is a schematic explanatory diagram of a practical example of a hermetic coat. 14 Ni glass fiber 30: Carbon coat 32: Metal coat 1 Figure 13 [

Claims (1)

[Claims] 1) A hermetic coated optical fiber characterized in that a carbon coating layer and a metal coating layer are sequentially provided directly above a glass fiber for optical transmission. 2) The metal coating layer is a plating layer. The hermetic coated optical fiber according to claim 1