JPS5838373B2 - Hikarifu Ivano Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber used as a transmission line for optical communication, in which the refractive index of the glass material forming the outer periphery is determined at the outer periphery of the optical fiber made of a glass material containing silicic acid as a main component. It relates to uniformly coating a polymer with a lower refractive index and a surfactant.

Conventionally, it has been considered to coat the outer periphery of an optical fiber made of a glass material with a polymer for mechanical reinforcement, weather resistance, prevention of damage, and the like.

In this coating method, the film thickness of the polymer to be coated is several 1
00μ, so the extrusion molding method used in conventional electric wire coatings is suitable.

However, this coating method is not suitable for coating the following optical fibers because the interface between the outer peripheral portion of the optical fiber and the polymer does not adhere uniformly.

In other words, optical fibers with a small difference in refractive index between the core and the cladding (for example, optical fibers made of silicic acid-based glass materials such as fused silica glass, high silicate glass, and glass doped with fused silica with impurities such as phosphorus and titanium) optical fiber).

In this type of optical fiber, the cladding must be sufficiently thick because light is poorly confined in the core.

In this case, it is difficult to construct the cladding entirely of glass material because it is weak against mechanical bending and easily breaks, and it is necessary to supplement a portion of the cladding with a high molecular weight polymer.

However, with the above coating method, it is difficult to obtain uniform adhesion or close contact between the outer peripheral part of the optical fiber made of glass material and the interface of the polymer, and imperfections such as inclusion of air bubbles occur, and the scattering loss of light increases due to these imperfections. However, the optical transmission loss deteriorates.

Furthermore, the coating easily peels off from the optical fiber.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing an optical fiber that has good adhesion between the outer peripheral part of the optical fiber made of a glass material containing silicic acid as a main component and the high molecular weight polymer coated on the outer peripheral part. .

In other words, it relates to coating the outer periphery of an optical fiber made of a glass material containing silicic acid as a main component with a polymer having a refractive index lower than that of the outer periphery. The present invention provides a novel method for manufacturing an optical fiber, which is characterized in that a surfactant is present in a solution of a high molecular weight polymer when coating glass with the same.

According to the present invention, the use of a surfactant makes the surface of the outer periphery of the optical fiber less susceptible to water, and improves the adhesion or adhesion of the polymer to the outer periphery of the optical fiber.

Therefore, scattering loss due to imperfect adhesion at the interface between the optical fiber made of glass material and the high molecular weight polymer is reduced.

The reason why polymers do not adhere well to glass is
Due to water molecules attached to silanol groups on the glass surface through hydrogen bonds, etc., the apparent surface energy of the glass surface decreases, and the polymer does not wet the glass surface uniformly, causing the glass and polymer to adhere to the molecular order. This is thought to be due to the inability to approach the area.

In the present invention, a polymer having a refractive index lower than that of the outer peripheral portion of an optical fiber made of a glass material is used.

An example is polyvinylidene fluoride (nD=1.
4 2).

This is used by dissolving it in N,N-dimethylformamide.

Further, a cationic surfactant such as alkyldimethylbenzylammonium chloride was used as a surfactant.

Although there are many unknowns as to why the above problems were solved by using surfactants, it can be considered as follows.

The surfactant selectively adsorbs on the glass surface, reducing the sensitivity of the glass surface to moisture, making it possible to create a uniform surface condition on the glass surface, and the high affinity between the surfactant and the polymer. , the adhesion between the glass and the polymer is improved.

The same effect can also be obtained by treating an optical fiber made of glass material with the above-mentioned surfactant and then coating it with a polymer.

EXAMPLE FIG. 1 shows a method of coating an optical fiber with a polymer.

A method for manufacturing an optical fiber will be explained using FIG.

An optical fiber 2 made of glass material (core: fused silica glass, nD-1.458
5. Diameter 80μ: Clad: High silicate glass, nD=1
4575 (thickness: 30μ) is passed through an optical fiber cleaning tank 3 containing trichlorethylene and dried with a heater 4.

Then, 0.2% (weight) of alkyldimethylbenzylammonium chloride was added to polyvinylidene fluoride.
1070 (weight) N of polyvinylidene fluoride
, passed through a polymer tank 5 containing an N'-dimethylformamide solution and dried with a heater 6.

The polymer tank 7 does not contain the above-mentioned surfactant.

The optical fiber coated with the polymer is baked at 210° C. by a baking heater 8 to coat the optical fiber with a polyvinylidene fluoride film of about 15 μm, and then wound onto a winding drum 9.

The optical fiber obtained in this example had uniform adhesion (close contact) between the outer circumferential part of the optical fiber made of glass material and the interface of the polymer, and there were extremely few air bubbles, voids, and dust contamination, which would be the center of light scattering. was observed.

Also, because of the good adhesion between the glass and the polymer, it is an optical fiber that is more resistant to mechanical bending.

Note that in order to coat the film with a thicker polymer, a larger number of polymer layers may be used or the concentration of the polymer solution may be increased.

As a further alternative, a combination of the above coating method and extrusion or forming method may be used.

As described above, according to the manufacturing method of the present invention, the outer periphery of an optical fiber made of a glass material can be coated with a high-molecular polymer with good adhesion.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the optical fiber coating method of the present invention. 1... Optical fiber delivery drum, 2...
... Glass fiber, 3 ... Optical fiber cleaning tank, 4 ... Heater, 5 ... Polymer tank containing surfactant, 6 ... ...Heater, 7...
... High molecular polymer tank, 8 ... Baking heater, 9
...Optical fiber winding drum.

Claims (1)

[Claims] 1. When coating the outer circumference of an optical fiber made of a glass material containing silicic acid as a main component with a polymer having a refractive index lower than the refractive index of the glass material forming the outer circumference, the An optical fiber manufacturing method characterized by coexisting a cationic surfactant in a solution.