JPS6016828A - Manufacture of optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having long length and high strength, by spinning an optical fiber from a preform composed mainly of SiO2 in an inert gas atmosphere using a high-purity carbon as the heating element, and passing the fiber through a hot atmosphere containing oxygen. CONSTITUTION:A gas such as argon gas is introduced into the furnace 1 through the gas inlet 3 to keep the inside of the furnace to the inert gas atmosphere, and the furnace is heated at about 2,000 deg.C with the heating element 2. An optical fiber preform 7a composed mainly of SiO2 is inserted slowly into the heated atmosphere, and the molten lower end of the preform is drawn at a high speed to form an optical fiber (b). An oxygen-containing hot atmosphere is formed just below the furnace 1 with the heater 4, and the spun optical fiber 7b is passed through the atmosphere. Accordingly, the impurities attached to the outer circumference of the optical fiber 7b is burnt and removed in the oxygen-containing hot atmosphere. The lowering of the strength of the optical fiber 7b caused by the deposition of impurities can be solved by this process.

Description

[Detailed Description of the Invention] The present invention provides a long, long, high-strength optical core □( )<75'
Regarding the method by which it can be manufactured.

As is known, when manufacturing quartz-based optical fibers, a single piece of quartz yarn having a core part and a cladding part is spun (heated and drawn), and the core part is made of quartz and the cladding part is made of Buranuchik. In the production of plus-gold clad fiber, a quartz-based cladding fiber is spun, and the outer periphery of the core immediately after the spinning is coated with a cladded cladding.

Usually, a carbon resistance heating furnace, a zirconia (ZrO2) induction 11i1 heating furnace, etc. are used as the heating furnace for spinning. By the way, among the light beams produced in the above manner, γ is 500 positive < q / mrl (light that emits a tensile slackness of 4 degrees + X1) γ. A.2 is obtained, but IKm
It is difficult to maintain the above-mentioned strength over the entire length of a long material with a tensile strength of 35 to 70 kg/f, and due to the cleaning test after spinning, the strength is 35 to 70 kg/
s1. It has remained to a certain extent.

The reason for this could be something like Haggi.

In other words, the above-mentioned heating furnace provides a high-temperature heating atmosphere (200
This is because when producing a high temperature (around 0℃), the materials in the furnace evaporate due to high temperature heat and become impurities, which become deposited on the optical fiber base material or the surface of the optical fiber and create defects. This is because the number of defects generated increases in proportion to the length of the optical fiber.

In view of the above-mentioned problems, the present invention has been developed to obtain a long optical fiber with high strength by eliminating the cause of strength deterioration during optical fiber manufacturing by JJI. Let's explain by example.

Figure [Here, (1) is a heating furnace for heating the optical fiber base material, and a heating element (2) made of high-purity carbon is placed inside the heating furnace (1). The same reactor (
1) There are several m supply ports (3) for supplying an inert gas (for example, Ar) into the interior (even one is f, Vs
) The provided heater (4) is an oxyhydrogen flame type heating heater consisting of a ring burner or the like, and this heater (4) is placed immediately after the heating furnace (1).

(5) is a die coater installed after the heater (4);
) is a coating curing furnace located after the die coater (5). In the present invention, in the above heating furnace (1), there is a supply port (3
) to keep the inside in an inert gas atmosphere, and heat the inside to about 2000°C from the heating element (2). SiO□ is the main component in this heated atmosphere. The optical fiber base material (7) a is gently inserted and its melted end (lower end) is stretched at high speed to form an optical fiber ((7) b). Due to the high temperature, carbon particles evaporated from the heating element (2) arrive as impurities, but immediately after the heating furnace (1), a heating atmosphere containing oxygen is generated in the heating element (4). Since the optical fiber (7)b after spinning passes through this, impurities adhering to the outer periphery of the optical fiber (7)b are burned and removed in the oxygen-containing heated atmosphere. The cause of strength deterioration due to impurities in the optical fiber (71b) is eliminated.

When using the oxyhydrogen flame type heater (4), the oxygen content in the heating atmosphere is 30 vot% or more, preferably 50 vot% or more, and 02/H
The ratio of 2 is about 3/2.

In addition, the humidity of the oxygen-containing heating atmosphere is set to 700°C or higher, but if the plate edge is heated to a temperature of 2000°C or higher, the outer diameter of the optical fiber (7) b will change, so the upper limit is 1700°C or higher.
It is best to keep it at around ℃.

Optical fiber after impurities have been removed as described above (
7) b completely passes through the die coater (5), and here the coating y (
(for primary coat, buffer coat, etc.) will arrive in January,
Further, the coating film is cured in a coating curing furnace (6) in the next stage to form a predetermined coated optical fiber (7)c.

In addition, although the heating furnace (1) was used as a carbon resistance heating furnace in the above, this may be a zirconia induction heating furnace.

However, in the case of a zirconia induction heating furnace, a furnace tube made of surface-purity carbon is provided to prevent particles evaporated from ZrO2 (which cannot be removed by combustion) from adhering to the optical fiber base material or optical fiber. Further, when creating an oxygen-containing heating atmosphere, a CO2 laser or the like may be used as a heat source, and in this case, a predetermined amount of oxygen is supplied to the heating atmosphere.Next, Examples and Comparative Examples will be described below.

As is clear from the table above, Example 1.2 of the present invention, in which the optical fiber after spinning is passed through an oxygen-containing heated atmosphere and subjected to a predetermined treatment, and Comparative Example 1.2, in which such treatment is not performed. Compared to the previous version, its opening strength has been significantly improved.

As explained above, the present invention is a method for producing an optical fiber by spinning an optical fiber base material mainly composed of SiO2 by heating and drawing, in which high-purity carbon is used as a heating element or a furnace tube, and an inert gas is used. An optical fiber is produced by spinning the optical fiber base material in a heated atmosphere using an atmospheric gas, and the spun optical fiber is passed through a heated atmosphere containing oxygen to remove impurities attached to the optical fiber. Because of this characteristic, there are almost no strength defects caused by impurities, and therefore, high-strength long optical fibers can be manufactured at a good yield.

[Brief explanation of drawings]

The drawing is an explanatory diagram schematically showing one embodiment of the method of the present invention. (1)・・・Heating furnace (2)・・・Heating element (3) Inert gas supply port (4)・・・Heating device (7) a... Optical fiber base material (Force b...Optical fiber Patent issued, applicant Agent: Patent Attorney Makoto Ifuji

Claims (1)

[Claims] tl) A method for producing an optical fiber by spinning an optical fiber base material containing SiO□ as a main component by heating and drawing,
The above-mentioned optical fiber base material is spun into an optical fiber in a heating atmosphere using high-purity carbon as a heating element or a furnace tube and an inert gas as an atmospheric gas, and the spun optical fiber is heated in an oxygen-containing atmosphere. A method for manufacturing an optical fiber in which impurities attached to the optical fiber are removed by passing the fiber through the atmosphere. The method for manufacturing an optical fiber according to item 1. (3) The humidity in the heated atmosphere containing 1-sulfur is 700%.
], 700° C. The method for manufacturing an optical fiber according to claim 1 or 2.