JPS6186437A - Manufacturing method of optical fiber base material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Blue electricity and object 1 of the invention]
The invention relates to a method for manufacturing materials.

Generally, a method for manufacturing optical fiber mother H by VAD method 4J
There is a significant difference in productivity. Then, raw gas such as silicon chloride (S!Cf' 4 ), which becomes the base glass, and germanium chloride (GeCj!t) and chloride oxide P'l (P OC = 1) to control the refractive index.
etc. are reacted with the heat of an oxyhydrogen flame, etc.,
The glass fine powder produced by this reaction is sequentially deposited on the tip of the target, and the temperature distribution at the tip of the target controls the radial refractive index distribution of the final glass. Therefore, controlling the temperature of the first tip has a large effect on the transmission characteristics of optical fibers made from the optical fiber base material, especially on the transmission band characteristics of multimode graded optical fibers. I especially like it.

Conventionally, methods for adjusting the 11-beat conditions at the leading edge of the gas to a constant level have been proposed, and for example, for controlling the reaction temperature at the leading edge, it is currently within the range of ±1 to 2°C. The adjustment technology has almost been established, and the reproducibility of the characteristics is also good.

However, there are still many problems in improving the reproducibility of band characteristics and improving the yield of wide area fibers, and the results are not necessarily satisfactory.

The present invention has been made in view of the above situation. The object of the present invention is to provide a method for manufacturing an optical fiber base material that can significantly improve the reproducibility of the band characteristics of a radial mode graded optical fiber and the yield of broadband fibers.

[Summary of the Invention] The optical fiber manufacturing method of the optical fiber 1117 uses an oxyhydrogen flame rl+ in which oxygen and hydrogen are fed into an oxyhydrogen burner and burned.
't') A raw material gas such as 7A silica and germanium chloride is reacted to produce a glass fine powder, and the glass fine powder is produced.
When producing a 1-length optical fiber by pushing the end of the fiber into the tip of the target (i) to form a porous base material, and heating and transparentizing the porous 1m material, 13+j of stone gas is added to ■-1. The reaction takes place in the chamber and the accumulation of the fine glass powder continues. - Periodically change the internal pressure in the chamber!11
This is a method of changing the refractive index distribution index α of the above-mentioned glass fine powder material in the longitudinal direction.

[Example] Hereinafter, the method for manufacturing an optical fiber preform of the present invention will be explained using an example and FIG. 1. FIG. 1 is a longitudinal sectional view of the implementation device. In the figure, 1 is the target, 2 is the chamber,
3 is a porous base material (soot) made of deposited glass fine powder, and 4 is the tip of the porous base material of the deposited glass fine powder layer, which is the highest temperature point. 5 is a window for measuring the reaction temperature of the porous base material 3, 6 is an infrared temperature measuring device, 7 is an oxyhydrogen gas flow rate adjustment device, 8 is a quartz tube burner, and 9 is a chamber stand.

10 is the exhaust gas and 0.11 is the pressure sensor inside the chamber 9.

12 is an internal pressure adjustment device, and 13 is an internal pressure adjustment drive circuit.

14 (It is an oscillator. The quartz tube burner 8 is located at its center 7'
ijl Harno to Dlr R gas 3 i C1! a
, GeCl1i.

1-)OCI! :], etc., and from the outer tube burner, oxygen and water;
It has a composite burner structure with two gas outlets).

This example describes the method and responsibility of the conventional optical fiber base material.
This is done by reducing the internal pressure within the chamber 2, which is causing the reaction of the 1000,000 yen raw material gas during the deposition of the porous base material (soot) 3, by a circumferential increase of +11 J. ), it is a fish that gives periodic changes to the volume conditions of one glass fine powder.

Then, the raw material gas, oxygen, hydrogen, and other gases are fed into the quartz burner tube 8, and the stone scum is reacted in an oxyhydrogen flame at the port 11, and the tip of the turret 1, which is passed through the Φλ once, is exposed to the tip of the turret 1. A porous layer is created by gradually pulling up the final layer of sediment. T t* (Δ3 is formed; on the other hand, the acid used in the combustion, ); and hydrogen, )) & the gas of argon, nitrogen, or purified glass ( part of the end', r;
4. L No 1 Ki Ro 10 to 1 No 1 issued.

Under normal conditions, oxygen is 8,5f! /min, hydrogen is used at a flow rate of about 1.5 J/min, and further,
The flow rate of hydrogen (if the temperature at the highest temperature point of the porous base material tip 4 of the layer of glass particles deposited on the target 1 is 1.0
The temperature is adjusted to 20°C.

In addition, the internal pressure in the reaction chamber 2 is measured by a pressure sensor (internal pressure measuring device) 11, and by driving the internal pressure adjustment device 12 via the internal pressure adjustment drive circuit 13, the internal pressure is normally adjusted to 1.0 mmHzO compared to the indoor pressure. is kept constant at a low value.

Figure 2 shows the refractive index distribution index α at each wavelength on the horizontal axis and the band on the vertical axis to show the relationship between the two. ) rl, 3 μm band grade is a graph derived from the theoretical equation q published in ``Optical Fiber Manufacturing Technology''. In FIG. 2, the solid line curve has a wavelength of 0.82 μm, and the dotted line curve has a wavelength of 1.2 μm. It can be seen from the figure that the range of the refractive index distribution index α is very narrow and roughly 7. Since the optics of the i+ wavelength and the ultra-wavelength l+Cj are slightly different from each other, it is difficult to improve the reproducibility of so-called double-window type manufacturing, which aims to widen both wavelength bands, as well as to widen each wavelength band. I can guess whether it is.

In this embodiment, the electric signal from the generator (Tatsu'a 171) is vibrated at a period of approximately 2 minutes, and the internal pressure inside the chamber 2 is -1.0 to -3.0 mmHz O compared to the indoor pressure. A porous base material (soot) 3 was manufactured in which the refractive index distribution index (χ) was varied in the longitudinal direction with a periodic variation in the range of . It has been confirmed through experiments that the refractive index α varies within a range of ±0.05 in the longitudinal direction.

The optical fiber manufactured from the optical fiber base material subjected to 'FFJ m' as described above should have a refractive index distribution index α changing in the longitudinal direction at a period of about 200 to 300 m, but this When we examined the change in band characteristics in the longitudinal direction by cutting into sections, we found that the fluctuation range was small and the proportion of broadband characteristics was significantly improved. In particular, a double wind tie bouffe that can be used both long and short? The yield of fiber optics has been significantly improved, and the bandwidth deterioration index for long-distance transmission (
It was also found that γ: 0.5≦γ≦1) was smaller than that of conventional products, making it suitable for long-distance transmission. In addition, it has been recognized that there is almost no difference in characteristics other than band characteristics, such as 10 loss characteristics during connection, stress resistance characteristics, temperature characteristics, and 1ξ1 loss characteristics at room temperature, compared to conventional products. There is.

On the other hand, in a multi-mode graded optical fiber in which the index of refraction α varies in the longitudinal direction, the optical fiber propagating each mode easily causes coupling, and the uni-integral relationship between the modes increases. It is well known that the delay time difference can be reduced and a wider band can be achieved. However, even if the temperature at the tip of the target is precisely controlled to a constant level, due to subtle differences in other manufacturing conditions,
The refractive index distribution index α is controlled to be constant at a point where it deviates from the target value, and a narrow band appears at the 8i end. Iba often yelled. Also, the variation in band characteristics in the longitudinal direction is also large. According to the method of Kinomi 1, the refraction weight/li index α does not deviate to a constant value, and even when it deviates slightly, the refraction ('ko distribution index α
Because of the periodic fluctuations, there will be no more extreme blazes.

According to the method for manufacturing the optical fiber preform of this embodiment, the optical fiber preform after being made transparent is produced by periodically varying the internal pressure in the dilenver and varying the Ht and vi conditions of the fine glass powder. The refractive index distribution index α of the material can be varied in the longitudinal direction, and the yield of fibers with -C broadband characteristics is greatly improved, and longitudinal changes in the band characteristics are reduced.

42i, the yield of both long and short-purpose fibers has been significantly improved, and the band characteristic index γ, which deteriorates as the length of transmission increases, is smaller than that of conventional products, making it 7111h.
Suitable for il transmission.

"Effects of the Invention" As described above, the method for manufacturing the optical fiber preform of the present invention 71
．． According to this method, the reproducibility of band 14 characteristics of multimode graded optical fibers and the yield of wideband fibers can be significantly improved.

[Brief explanation of drawings]

Figure 1 is a new view of a device for carrying out the method of manufacturing IJ of the present invention, and Figure 2 is a new view of the equipment for implementing the method of manufacturing IJ of the present invention. It is a graph of a theoretical calculation formula showing the relationship between the refractive index distribution index α and the band. 1...Target, 2...Chi1! Nba, 3... Porous 7'TL1 month. 8...Quartz tube burner, 11...Pressure sensor, 12...
...Internal pressure adjustment device, 13...Internal pressure adjustment drive circuit. Shu V ≠

Claims (3)

[Claims] (1) Oxygen and hydrogen are fed into an oxyhydrogen burner, and raw material gases such as silicon chloride and germanium chloride are reacted in the burning oxyhydrogen flame to generate fine glass powder, and the fine glass powder is deposited on the tip of the target. In the method of producing an optical fiber preform by forming a porous preform by heating and making the porous preform transparent, the reaction of the raw material gas is carried out in a chamber, and the deposition of the fine glass powder is continued. The refractive index distribution index α of the optical fiber preform after being made transparent is changed in the longitudinal direction by periodically varying the internal pressure in the chamber and changing the estimation conditions of the glass fine powder. A method for manufacturing an optical fiber base material. (2) The period of varying the internal pressure in the chamber,
The method for manufacturing an optical fiber preform according to claim 1, wherein the length of the finished fiber is 500 m or less. (3) The range in which the refractive index distribution index α is changed is ±0.
01 to ±0.1. The method for manufacturing an optical fiber preform according to claim 1.