JPS60186426A - Manufacture of optical fiber - Google Patents

Abstract

PURPOSE:To decrease the number of production apparatuses, shorten the production time, and manufacture an optical fiber at a high speed, by carrying out the vitrification and the drawing of an optical fiber simultaneously. CONSTITUTION:A porous preform attached to the seed rod 3 is inserted into the electric furnace 1 acting also as a drawing furnace, and is vitrified to a transparent glass 6 by introducing an inert gas into the furnace through the gas inlet. The preform is drawn to an optical fiber simultaneous to the vitrification process 6. The temperature distribution in the drawing zone is maintained at about 1,900-2,000 deg.C. An optical fiber can be manufactured economically at a high speed by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for manufacturing an optical fiber in which a transparent vitrification process and a drawing process are performed simultaneously when manufacturing an optical fiber.

(Prior art) There are many types of optical fiber manufacturing methods, such as Vapor-Phase Axial Deposit
In the ion (V A D ) method and the external attachment method, optical fibers are manufactured by the following steps.

(If raw materials are reacted at high temperature to generate fine particles,
The process of depositing which forms a porous matrix.

(I [l A step of heating the porous base material to make it transparent vitrified.

(II) A step of drawing the transparent vitrified base material into an optical fiber.

It has already been reported that the steps (I) and (Ill) are performed sequentially, but (I), (Ill, (It
) process remains the same, and two electric furnaces are required.

In the conventional method, the steps (II) and (Ill) are separated because the processing temperatures in both steps are different [for example, about 1600°C in (Ill) and 2000°C in (■).
It is thought that the temperature is close to °C]. However, by performing both processes separately, two completely different types of electric furnaces are required, and the time required is 2 to 8 times longer than when both processes are performed at the same time. .

Another reason why the idea of performing the (Ill and (ml) processes at the same time did not arise is that Gemg, etc., which are used as dopant for optical fibers, volatilizes when turned into transparent glass at a temperature higher than 1600"C. This was because there was a mistaken belief that the

(Purpose of the invention) The present invention is directed to transparent vitrification and optical fibers! ! It is characterized by performing I@ simultaneously, and its purpose is to reduce the number of devices and shorten manufacturing time, and to manufacture optical fibers at high speed.
The aim is to achieve lower prices.

(Example 1) In order to combine process (Ill) and process (11), it is first necessary to demonstrate that transparent vitrification is possible without volatilization of the dopant at a higher temperature than the conventionally said 1600"C. There is.

Using the electric furnace (carbon resistance furnace) 1 shown in FIG.
2 was inserted and fixed on the seed rod 8.

Inert gas (Ar+He) is introduced from the gas inlet 4,
Transparent vitrification was performed at various temperatures. The refractive index distribution of the transparent vitrified sample was measured using an interference microscope, and at the same time, the Goog concentration was determined by chemical analysis.

Figure 2 shows n/n5 (n:
Refractive index of the central part of the sample vitrified at temperature T, n8F 1
The refractive index of the central part of the sample vitrified at 450°C is expressed as a percentage. The arrow in the figure indicates the temperature (1900 to 2000'C) when drawing the optical fiber.

At temperatures below 2000°C, almost no change in the refractive index was observed, and it was found that there was no problem with the volatilization of GeO2 even if vitrification was performed at the same temperature as that for drawing.

FIG. 8 shows the results of examining the shadow 1 of the transparent vitrification temperature using the refractive index distribution in the radial direction of the sample. However, Δn represents a relative refractive index difference when quartz glass is used as a standard. 1460～
At 2000°C, it was found that there was almost no change in the refractive index distribution.

Furthermore, the results of chemical analysis were also consistent with the results of refractive index measurement.

(Example 2) A porous base material (S
ing-Gang) was semi-sintered in an electric furnace equipped with a quartz glass furnace tube to shrink the diameter to approximately Bow.

The temperature was 1800°C, and at that time, a salt fiber dehydrating agent was flowed into the furnace tube together with He gas for dehydration.

This semi-sintered porous base material was inserted into a wire drawing furnace and wire drawn.

No. 49 (al is a schematic diagram of this example, 1 is an electric furnace Cfm drawing furnace), 8 is a seed rod, 4 is a gas inlet, 6 is a semi-sintered porous base material, 6 is a transparent vitrified 7 indicates a portion where delineation is performed. Furthermore, Fig. 4fbl shows the temperature distribution in the electric furnace, where the line is drawn at the highest temperature position (1900-2000°C). The I-burning furnace uses carbon as a heating element and a carbon furnace tube, and the atmosphere is a mixed gas of lr and He5. The above semi-sintered porous base material was subjected to transparent vitrification and wire drawing at the same time in a wire drawing furnace.

FIG. 6 shows the optical loss wavelength characteristics of the optical fiber thus produced. In this example, only the core part is synthesized as a base material, and the cladding part is composed of silicone resin (usually used as a coating material), so the optical loss characteristics include absorption by OH groups (0, 95, 1, 24, 1
, 4 μml, absorption caused by the silicone resin can be seen.

The obtained optical fiber had a core diameter of 120βm1 and a silicone cladding diameter of 400 μm.

(Example 8) Using a wire drawing furnace with an inner diameter of about 59 m, transparent vitrification and wire drawing of a porous base material with a diameter of 50 g IK were performed simultaneously. First, set the position 20 degrees from the tip of the porous base material to the center of the furnace (this will be the position of the highest temperature).
By raising the temperature from room temperature to 1900°C, which is the drawing temperature,
I started drawing the line. Feed speed of porous base material is approximately 1~2n
m/min% wire drawing speed is 80-40 m/m
It was in. The loss value of the obtained optical fiber was almost the same as that of Example 2.

(Example 4) Using a porous base material (referred to as a fully synthetic porous base material) (about 60mm in diameter) in which a core part and a cladding part were deposited at the same time, wire drawing and transparent vitrification were performed simultaneously.

In this example, a few percent of the chlorine dehydrating agent was also He, Ar.
It flows at the same time as the gas. The obtained optical fiber was drawn with a core diameter of approximately 20 μm and an outer diameter controlled to be 125 μm.

FIG. 6 shows the optical loss wavelength characteristics of the optical fiber.

In FIG. 6, both the core part and the cladding part are made of glass, so the optical loss value is comparable to that of a normal optical fiber.

In the above example, an experiment was shown using a wire drawing furnace with a single chevron-shaped temperature distribution.
It is also possible to use an electric furnace (two-zone electric furnace) having two peaks of 1900° C. at the bottom.

As explained above, when manufacturing an optical fiber, the present invention simultaneously performs the process of converting a porous base material into transparent vitrification and the process of drawing it, so it is possible to significantly shorten the time required, compared to conventional methods. Instead of two electric furnaces, only one is required.

This is a great advantage when trying to manufacture optical fibers in large quantities at low cost.

[Brief explanation of drawings]

Figure 1 is a schematic of the transparent vitrification experiment (Example 1). Figure 2 is n/n8 with respect to the vitrification temperature (n: refractive index of the central part of the sample vitrified at temperature T, n8: at 1450°C). FIG. 8 is a diagram showing the influence of the transparent vitrification temperature on the refractive index distribution. FIG. 4(a) is a schematic diagram of an embodiment of the present invention. Figure 4 (b
) is a diagram showing the temperature distribution in the electric furnace, Figure 5 is a diagram showing the optical loss wavelength characteristics of an optical fiber (silicone cladding) obtained by simultaneously performing transparent vitrification and drawing, and Figure 6 is a diagram showing the optical loss wavelength characteristic of the optical fiber obtained by simultaneously performing transparent vitrification and drawing. FIG. 3 is a diagram showing the optical loss wavelength characteristics of an optical fiber obtained by simultaneously performing transparent vitrification and drawing using a porous preform prepared by the above method. 1... Electric furnace, 2... Porous base material, 8... Seed rod,
4... Gas inlet, 5... Semi-sintered porous base material, 6...
... Part where transparent vitrification is performed, 7... Part where line drawing is performed. (8) Fig. 2 74 Kaisho GO-186426 (4) Fig. 3

Claims (1)

[Claims] L: Generate glass particles by reacting glass raw materials, deposit the glass particles to form a porous base material for optical fiber, and then turn the porous base material into transparent vitrification in an electric furnace for drawing. 1. A method for manufacturing an optical fiber, the method comprising: drawing an optical fiber.