JPS58167441A - Production of optical fiber - Google Patents

Abstract

PURPOSE:The parent material is heated with an oxyhydrogen flame on its surface and simultaneously a SiO2-TiO2, SiO2-ZrO2 glass layer is formed on its surface and the resultant material is made into filaments to produce optical fiber with increased long-term reiliability and improved minimum strength. CONSTITUTION:A quartz parent material for optical fiber 1 is heated with an oxyhydrogen flame 4 from the burner 3 on its surface and simultaneously the material is coated with a glass layer of SiO2-TiO2 or SiO2-ZrO2 on its surface using a SiCl4-TiCl4 or SiCl4-ZrCl4 gas. Then, the resultant parent material is made into the objective optical fiber. This process facilitates the cable formation of fiber connection in optical fiber production.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an optical fiber with excellent long-term reliability.

Conventionally, since optical fibers are generally made of extremely brittle materials, they tend to have surface scratches, which become a stress concentration source and easily break. To solve this problem, a method has been proposed in which an optical fiber with high initial strength is manufactured by applying a glassy liquid immediately after spinning the optical fiber to protect the surface of the fiber. Normally, this plastic lateral structure consists of an eight-layer structure consisting of a primary coating, a buffer layer, and a secondary coating. The purpose of the buffer layer is to improve the workability of the cable, and to prevent an increase in transmission loss when cabled.

The tensile strength when a primary coating is applied to an optical fiber without a stress concentration source is 5ookl? Non-NK has a high strength of about 1 IES / dew, but since commercially available products are generally used for the cladding glass of optical fibers, there are many small silver bubbles and surface scratches, and therefore there is a stress concentration source at present. It is almost impossible to obtain k without an optical fiber. Therefore, the initial li! of the optical fiber subjected to one modulus! Jf is
It varies in the range of 100 kfI/ff1- to 50 Ok&/m-. Furthermore, it is known that optical fibers made of a small amount of certain types of plastic among primary covering materials suffer a decrease in strength simply by being left in water or in a high-temperature atmosphere. When using an optical fiber that causes such a one-dimensional variation in initial strength or a decrease in strength as an optical transmission medium, there is a risk that it will not be able to withstand long-term practical use.

Furthermore, when connecting optical fibers, the plastic coating is removed before connection, but there is a drawback that it is not easy to remove the 1-module component.

The present invention heats the surface of a base material for a silica-based optical fiber with an oxyhydrogen flame, and at the same time, heats the surface of the base material with 8i0-Tie.
House or 810. - It is characterized by forming a ZrO and glass layer, and its purpose is to solve the above-mentioned problems, improve the optical fiber's minimum 9M degree, improve long-term reliability, and simplify the fabrication of cables and connections. There is a K when it becomes .

The present inventors first investigated the strength of a quartz fiber and a quartz fiber having a core and cladding, and found that the strength is related to the stress in the fiber, and further depends on the compressive stress on the surface of the tougeshike fiber, increasing the strength. It was discovered that the compressive stress can be increased to achieve this effect. Stress in the fiber is caused by the difference in the thermal expansion coefficients of the core and cladding glass.The thicker the line, the greater the stress, and the compressive stress on the fiber surface means that the thermal expansion coefficient of the core glass is greater than that of the cladding glass. However, in normal silica-based original fibers, the refractive index difference between the core and the cladding (thermal III expansion coefficient), the composition of the cladding glass (usually (810.1 component) and thickness, the compressive stress on the fiber surface can only be expected to be constant Fkfl.

The present invention provides a glass layer having a lower coefficient of thermal expansion and a higher refractive index than the cladding layer, that is, 810, -Tie, on the surface of the base material for a silica optical fiber (the surface of the cladding layer).
or 810. - Provides a method for forming a ZrO, glass layer, thereby improving the fiber surface thl
This applies a compressive stress greater than K.

FIG. 1 shows a method of forming a layer of 81O glass yarn added with KTie or ZrO on the surface of an existing optical fiber base material, that is, an embodiment of the present invention. , l is an existing quartz-based optical fiber base material, 3 is a glass lock, 8 is an oxyhydrogen burner, and 4 is an oxyhydrogen flame.

The base material 1 for silica-based optical fiber is manufactured by VAD method, MCVD method, and Rond-in-tube method, which are typical manufacturing methods of optical fiber, and the dimensions of the core and cladding are already determined. It is. Conventional silica-based optical fibers are obtained by flame-polishing the surface of an optical fiber base material 1 with an oxyhydrogen flame 4 to remove surface scratches and microbubbles as much as possible, as shown in Figure 1g1, and then spinning the fiber. Ta.

The present invention provides a method in which, in the above step, the glass raw material is introduced in a vapor phase into the oxyhydrogen burner 8 at the same time as the flame polishing, and the resulting oxidation reaction is caused to adhere to the surface of the optical fiber base material l. According to the present invention, the glass layer according to the present invention is formed at the same time as removing surface scratches, so that the effect of flame polishing is added to the strength improvement due to high compressive stress.

The thickness of the glass layer according to the present invention is as follows:
Since it can be controlled by the uniform speed of the oxyhydrogen burner 8 that moves in the axial direction of the T10. The doping amount of ZrO and ZrO can also be changed arbitrarily.

FIG. 1 is a perspective view of an optical fiber base material having a glass layer produced according to the present invention, where 1 is a quartz-based optical fiber base material, and 81 is a glass layer according to the present invention.

Next, the present invention will be explained using specific examples.

Specific example-1 H gas is supplied to an oxyhydrogen burner at g Oj/min, -0, gas is 10 J/mln, 81 Cj is used as a glass raw material, and TiCJ.

were guided in a gaseous state, and an oxyhydrogen flame containing a gaseous glass raw material was sprayed onto the surface of a quartz-based optical fiber base material (core system: 1-0111 mφ, outer diameter: 11,611 mmφ) rotating at l 5 rpm. The oxyhydrogen burner was moved in the axial direction of the silica-based optical fiber base material at a speed of g mia per minute. During this process, the surface temperature of the base material was measured and found that the temperature of the heated part was approximately 2100°C and 810°C. −
Tie, the temperature was sufficient to make the glass transparent. length f
After moving the oxyhydrogen burner over iO(m), the surface of the base material has a temperature of 5K as shown in Figure 8.

810, - Tie, glass is formed and its thickness is 0
．． It was 4rILm. The outer diameter of this is 129μ using a spinning machine.
Spinning was carried out at mK setting, and in a subsequent step a silicone resin was coated as a buffer layer.

The tensile strength of the obtained optical fiber was 10.0 at a length of 60
As a result of this measurement, their strength was [450 to 500]
The minimum strength was improved, and the result was that the strength was high and the 1 variation was very small. In addition, by connecting these fibers, workability is improved. As a result, the silicone rubber buffer layer can be easily removed, and the strength of the fibers has increased, making the work much easier. Time has also been shortened.

5ICj4 and ZrCI4 as glass raw materials were introduced into an oxyhydrogen flame in a gaseous state, and 810. - A ZrO and glass layer was formed, the obtained base material was spun, and the tensile strength was measured. As a result, uniformly good results were obtained as in Specific Example-1.

In addition, BiO-ZrO and glass have excellent alkali resistance, so the fiber obtained by the present invention and the conventional fiber)
When immersed in Js OH for an IAO time, the dissolution rate of the fiber obtained according to the present invention was slower than that of the conventional fiber.

Note that in both Specific Example 1 and Specific Example 8, a base material in which a core and a cladding are integrated is used as a starting material, but a glass layer is formed by the present vIsK on the surface of a quartz tube that is to become a cladding layer. However, the same result was obtained when the core part was then inserted and used as a base material for Hikari 7 Eyepa.

As explained above, the method for manufacturing an optical fiber of the present invention involves heating with an oxyhydrogen flame and simultaneously flame polishing the 810-TiO
Alternatively, a glass layer of 810-ZrO is formed on the surface of the base material for optical fiber SS, so the glass layer can be formed very easily, and by spinning this base material, the minimum Strength can be improved. As a result, it is possible to improve the long-term reliability of the optical fiber. Also 810. -An optical fiber having a ZrO and glass layer has the advantage of high alkali resistance.

Furthermore, the glass layer according to the present invention
Since the primary coating plays the same role as the secondary plastic coating layer, the primary coating is unnecessary in the process of spinning the base material in which the present invention is carried out, and it is possible to simplify the spinning equipment, simplify the spinning operation, and This has the advantage that the working time can be shortened.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is a perspective view of a base material obtained by the present invention. 1... Base material for quartz-based optical fiber, 2... Glass lock, 8... Oxygen hydrogen burner, 4... Oxygen hydrogen flame, 21...
- Glass layer according to the invention. Figure 1 Figure 2

Claims (1)

[Claims] 1. At the same time as heating the surface of the base material for quartz-based optical fiber with an oxyhydrogen flame, 81Cj4-TiCj or 8iC
J4-ZrCj is deposited in a gaseous state to the surface of the base material for the quartz-based optical fiber. or 810. - A method for manufacturing an optical fiber, which comprises manufacturing an optical fiber by spinning a ZrO and glass layer.