JPS59195549A - Manufacture of base material for optical transmission - Google Patents

Abstract

PURPOSE:To manufacture a base material for optical transmission under-going little change in the refractive index due to its heat history by a CVD method by using a silica layer doped with a specified compound so as to make the refractive index lower than that of quartz glass as a clad. CONSTITUTION:A fluorine compound which is liq. or gas at room temp., contains boron, and does not contain hydrogen, e.g., boron trifluoride is used as a compound for doping. A mixture of silicon tetrachloride with said fluorine compound by <= about 40mol% of the amount of the silicon tetrachloride is fed to a reaction tube made of quartz glass using oxygen as a carrier, and it is indirectly heated to about 1,000-1,600 deg.C from the outside of the reaction tube to deposit a silica layer doped with said fluorine compound. The doped silica layer has a lower refractive index. A gaseous mixture of silicon tetrafluoride with oxygen is then fed to deposit a silica layer, and after raising the heating temp., the reaction tube is made solid by collapsing the hollow part of the pipe to manufacture a base material for optical transmission consisting of a doped silica clad and a silica core.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an optical transmission material having a doped silica layer as a cladding, which exhibits extremely little change in refractive index due to fA history.

Currently, high-purity quartz glass is mainly selected as a material for optical transmission because it has low loss due to absorption and scattering of the material itself, that is, light transmission loss.

In order to use glass as an optical transmission material, it is necessary to make the refractive index of the central part (core) of the glass (RM118), which is the constituent part of the optical transmission material, higher than that of the peripheral part (cladding). This structure takes advantage of the property that the light trapped in the core travels along the other glass fibers while repeating total reflection or refraction at the interface with the cladding. As methods for producing transmission materials, the rod-in-tube method and the chemical vapor IF reaction (CvD) method are known.

The rod-in-tube method uses straight quartz glass for the core, and a high-K, 11/1 glass tube known as Vycor glass for the cladding. We are developing materials for optical transmission. In this case, high-Si glass contains bubbles due to the manufacturing process, and scattering at the interface between the core and the cladding is large and the difference in refractive index is small, so there is no selectivity.

In order to manufacture an optical transmission path by the CVD method, the refractive index of the volatile silicon compound or the compound and quartz glass, which are the raw materials that form the main ingredient silica, is changed in reaction a, which is the substrate to which the reaction product is attached. The doped silica is discharged onto the wall of the reaction tube by reacting the doped silica, and on top of that, silica added with silica to increase the refractive index is precipitated. After growing to the required pJ, the hollow part is crushed to obtain a material for optical transmission, and the glass fiber is made into a glass fiber by a cutting process.

When quartz glass is used for the cladding, phosphorus, kermanium, titanium, aluminum, etc. are generally used as additives to increase the A[lI] ratio of the core. this@
If the refractive index of the cladding can be made lower than that of silica glass, the number of holes can be increased.

Since it is the core that the light follows, the core is the most jJ4 lost o>
It is preferable to use glass that is 11 mm thick, and it is best to use high-rise quartz glass.

A method is known in which U boron oxide is added to doped quartz glass using the CVD method to achieve a lower refraction than quartz glass, but this quartz glass doped with boron oxide is The drawback is that the refractive index changes due to heat history.

The present inventors solved the drawbacks of the above-mentioned syneresis method and
In order to provide a method for producing a material for optical transmission using a doped silica nozzle with a low refractive index constant at fc as a cladding,
We discovered a fluorine compound a7 suitable as a dopant for silicon tetrachloride, which produces silica through oxidation by external heating (indirect heating), and incorporated it into the present invention.
The gist of the present invention is that the fluorine ratio of a liquid or gas containing Q and B and/or nitrogen at room temperature is 7.
Doped silica is precipitated on the inner wall of a silica glass or high silica glass tube or on the outer open surface of a silica glass bale by oxidation of boiled silicon tetrachloride, and the precipitated silica is A method for manufacturing an optical transmission material characterized by using a silica layer as a cladding,
It is in.

In the method of the present invention, the B added to silicon tetrachloride is a liquid or gas at room temperature for convenience of handling, and it is hydrogen? Not including i:t'#
It is necessary to be J. Further, the mixing ratio of the fluorine compound to the silicon watermelon is in the range of 0 to 40% in terms of molar ratio, and if the mixing ratio exceeds this range, the discharge rate of the doped silica decreases, which is inappropriate. In addition, when silicon tetrachloride to which the above-mentioned Hupp compound has been added is introduced into a quartz glass tube or high silicate glass tube to carry out an oxidation reaction, in order to avoid contamination with moisture, the quartz glass tube or high silicate glass tube must be External heating (indirect heating) using hydrogen moxibustion, high frequency furnace, etc.

The heating temperature ranges from 1,000°C to 600°C.

First, 1 flJ of the method of the present invention will be briefly described.

The silicon tetrachloride is kept at a constant temperature in a constant temperature bath, and the silicon tetrachloride is mixed with ilA gas as a carrier gas and a predetermined amount of the above fluorine compound in a mixer and introduced into a quartz glass reaction tube. This reaction tube is externally heated with an oxyhydrogen flame, a 1% frequency furnace, etc. in order to accelerate the gas phase reaction rate.Furthermore, this reaction d is the reaction inside the reaction tube obtained as described above. As the product is precipitated, it is preferable to rotate at a constant speed using a rotating 4-1i groove as appropriate in order to ensure uniformity of the precipitation.After depositing the required thickness as a cladding, the supply of the fluorine compound is stopped. Then, high-purity quartz glass is deposited on the cladding using silicon tetrachloride σ) as a core.After performing the reaction precipitation in this way, the temperature of the foil is increased. The hollow part is crushed, and then a wire drawing process is performed to obtain a material for optical transmission.The core may be a high-purity quartz glass rod inserted into the precipitated cladding and left to form. If you want to increase the numerical aperture of the above-mentioned continuous light transmission material, use phosphorus or germanium to increase the refractive index of the core.

It goes without saying that the core can be formed by one person using a silica glass pellet containing elements such as titanium and aluminum in a cladding made of clay.

41: The invention is as described above (to provide a method for manufacturing an optical transmission material having a cladding layer made of doped silica with very little change in refractive index due to thermal history, and its industrial liquid value is 1. Next, the present invention will be explained in more detail with reference to real/J examples, but the wood fired HA cannot be extended to the following actual gun examples unless the number of times exceeds four.

EXAMPLE In a quartz glass tube (inner diameter 12 mm) set on a lathe and rotated at 60 rpm, trifluoride diluted with nitrogen gas to a concentration of 8 parts and having a molar ratio of 34 molar ratios to silicon tetrachloride and silicon tetrachloride was added. A mixed gas consisting of boron oxide was supplied at a rate of le per minute. An oxyhydrogen burner is placed in the quartz glass tube and moved at a speed of 8 cm for 1 minute in the direction of the flow of the mixed gas, heating the quartz glass to 1.35000 to remove doped silica that will become the cladding. It was precipitated. After repeating this heating by moving the oxyhydrogen burner 20 times, the supply of boron trisulfide was stopped and only the mixed gas of silicon tetrachloride and oxygen was passed through the quartz glass tube. After repeating the movement of the burner 40 times, the heating temperature was raised and the hollow part of the container was crushed to obtain a light transmission material.

The core diameter was 4.3 rrxie and the thickness of the doped cladding was 0.7 silk. Ion microanalysis detected 10 and 13 parts of fluorine and 2 parts of borosilicate in the cladding.

Also, the refractive index of this doped companion cladding is 1.453
5. That of the core was 1.4583. This material was drawn at 1,850°C5 at 40 m/min to give a refractive index of the dogged cladding in an excellent fiber, ri 1.4.
532, and the refractive 4-modulation before and after edging was smaller in the case.

Example 2 Quartz glass set on a lathe and rotated at 60 revolutions per minute.
(Circle diameter: 12 mrx) was supplied with a mixed gas of 100 cc/min of silicon tetrachloride and 500 cc/min of acid, and from 7r, an oxyhydrogen burner was placed on the quartz glass tube, and the mixed gas was moved in the direction of the IC. While moving at a speed of 10 cWL for 1 minute,
The quartz glass U was heated to 1.600°C, a silica layer doped with B and F was formed on the inner wall of the quartz glass tube, and the heating zone was moved by a 7'crh acid water cable burner for 5 minutes.
After repeating the process 0 times, the heating and the supply of the above-mentioned mixed gas were stopped, and a high-purity quartz glass plate (diameter 61) to serve as the core was inserted into the quartz glass j.

The quartz glass tube is heated with an oxyhydrogen burner and collapsed to form the high A11J (integrated with the quartz glass tube).
Mukawamen, (off a-obtained. The core diameter was 6.8 and the thickness of the doped cladding was U 1.3.) The fold is 1,4495, and that of the core is 1.4 s 8
It was 3. The refractive index of the cladding layer of the fiber drawn by drawing this material at 2,030°C and 40 ml for 1 minute is 1.
4495, history of refractive index before and after axial drawing 1Ii
I couldn't start B, and I lost 4 ciB/Km.

叉、ko(') 774 bar f 1.000'CKmMs
fa, u upper emperor Shin ζ, clad J-'s no Ifl refractive index is 1.4503, and it is 1 child! It was found that the fluctuations due to the four aircraft history are relatively small and can be ignored. In addition, in order to perform a component analysis of silica doped with boron trifluoride, -nori silicon chloride 100 cc/min, boron trifluoride,
35 cc4 Semi-JA500cc/min mixed gas 1.6
Chemical analysis of the silica produced by passing it through quartz glass heated at 00° CIC yielded B3.3 by weight.
It was found that it included Chi, Fl, and 4 regrets.

Comparative Example The same protection as in Example 2 was used except that 1 ton of boron chloride was used instead of boron trifluoride as a doping agent for the I-Pump in the mixed gas in the iC cannon area 2. make it
A transmission element] and a fiber were obtained.

The refractive index of the cladding material of Guaivar, which is the original transmission material, is 1.4545 and 1.4510, respectively, and fluctuations in the refractive index during the greening process are observed, making it difficult to use the original fiber as a direct fiber. It can be seen that the pattern increases from 0 and 11 on the optical transmission cable installations J and Ii to 0.15 on the fiber.

The same as 12 that implements this fiber *i, oooo
After adding .,'% to C, the refractive index of Cland I- increased to 1,4544 after slow cooling! %1jiJ口a! ″lto
, xt'vc lowered friend.

In this way, in the case of a fiber with a cladding layer doped only with B, the influence of heat flux is 4, and in practical use 1 (1 ≧
I understand that.

Patent developer Mitsubishi Metals Co., Ltd. Agent L3 Nao Kawa

Claims (1)

[Claims] (silica doped by oxidation by external heating of silicon tetrachloride doped with a liquid or gaseous fluorine compound at room temperature containing υ B and free of hydrogen)?GV3 wall or quartz of quartz glass or high silica glass A method for producing a material for optical transmission, characterized by depositing it on the outer surface of a glass barrel, and using the deposited doped silica layer as a cladding.