JPS62230641A - Production of optical fiber preform - Google Patents

Abstract

PURPOSE:To obtain the titled preform having high accuracy of refractive index distribution and producible at a high speed and low cost, by doping a specific preform with an element effective in varying refractive index and leaching the obtained cylindrical gel with an alcohol or its aqueous solution. CONSTITUTION:A preform produced mainly from an Si alkoxide is doped with an element effective in varying refractive index (e.g. Ge, Ti, etc.). The obtained sol 3 is poured into a vessel 1 having a lid 2 furnished with a central rod and gelatinized to obtain a tubular gel (wet gel, dry gel or sintered gel). the obtained sintere gel 13 is leached in a vessel 11 with a leaching liquid 14 consisting of an alcohol (e.g. ethyl alcohol) or its aqueous solution for about 5hr and the leached sintered gel is heated and vitrified in an electric furnace, etc. in the presence of a gas such as Cl and He, etc., to obtain the objective optical fiber preform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a base material for an optical fin by a sol-gel method.

[Conventional technology]

Conventional methods for manufacturing optical fiber preforms generally include the following methods.

■ MC'VD method (the village's method) Silicon tetrachloride, the dopant germanium tetrachloride, and oxygen gas are fed into a quartz tube, and when heated with an oxyhydrogen flame from the outside of the quartz tube, silica fine particles containing the dopant are adhere to. The dopant is continuously changed by 611 degrees for each deposited layer to obtain a refractive index distribution.

(Ovpo method (external method) Silica fine particles are formed on the surface of a quartz glass mandrel through a flame hydrolysis reaction, then the mandrel is removed and heated and melted, and the composition is controlled for each formation to create a refractive index distribution. get.

■ WAD method (vapor phase attachment method) Silica fine particles generated in a flame are deposited on the tip of the starting material to form a porous base material, which is made into a transparent base material in an electric furnace. When forming a solid base material, the refractive index distribution is obtained using the surface temperature distribution of the base material.

[4 points to be solved by the invention] However, in the conventional method described above, the manufacturing speed is slow and the cost is high.

In order to obtain a refractive index distribution, it is necessary to strictly control the flow rate of the raw material and the temperature of the oxyhydrogen flame, but there are problems such as difficult control.

Misfire 1 there! J4 is intended to solve this problem, and its purpose is to provide a method for manufacturing an optical fiber base material that has a high refractive index distribution, is fast in manufacturing speed, and is inexpensive. be.

[Means for solving problems]

Method for splitting optical fiber preforms according to the present invention In the production of optical fiber preforms by the sol-gel method, which uses alkoxides of silicon as main raw materials, a tubular preform to which an element that changes the refractive index of the preform material is added in advance is used. The method is characterized in that a gel (wet gel, dry gel, sintered gel) is produced, and leaching of the tubular gel is performed using alcohol or (d-alcohol aqueous solution).

[Example-1] The present invention will be specifically described below based on Examples.

To 208f (nomoles) of tetraethoxy 7 run and 101P (a4 moles) of tetraethoxygermanium, 60ml of aqueous ammonia having a pH of 10 and 500ml of ethyl alcohol are added and thoroughly stirred and mixed to form a sol.

This sol is poured into a polypropylene container with a rod shown in FIG. 1 and allowed to gel.

Here, 1 is a container, 2 is a lid with a center rod, and 3 is a sol.

After that, the center rod was pulled out and dried at a temperature of 50 to 70°C.
800CXI at a heating rate of 60℃/I (
H is sintered to form a sintered gel.

Next, leaching is performed as shown in FIG.

Here, 11 is a container, 12 is a lid, and 13 is a sintered gel 14 is a leaching solution (here, a solution of ethyl alcohol:water = 1:1). After a predetermined period of time, silicon and germanium ions in the leaching solution are removed by ICP. Perform standard analysis using a source emission spectrometer.

FIG. 5 shows the correlation between the elapsed time and one ion.

Here, 21 represents silicon and 22 represents germanium.

The sintered gel that had been leached for 5 hours was heated - day and night (18
After drying at room temperature for 9 hours, put it in an electric furnace and dry it at room temperature for 6
The temperature was raised to 00°C at a rate of 60°C/H, and the 4-element gas was heated to 1.
The mixture was held for 1 hour while flowing 5 L/M, then the temperature was raised to 900° C. at the same rate of increase, and the temperature was held for 30 minutes while flowing 0.517 M oxygen gas.

Furthermore, the temperature was raised to 950°C in the same way, and 1ti of helium gas was added.
It was vitrified by holding it for 30 minutes under yt (jrt).

, Figure 44 shows the refractive index values of various parts from the inner wall to the outer wall at this time.

Here, 31 indicates an inner wall, and 32 indicates an outer wall.

Next, by solidifying this glass and drawing it, a gray rad index type quartz fiber is obtained. The S loss was 20 dB/etc.

[Actual m row-2] Add 15% of 1N hydrochloric acid to 208f (1 mol) of tetraethoxy 7 run and 38f (12 mol) of tetraethoxy titanium.
Add 0 td, stir and mix thoroughly, and hydrolyze to form a sol.

This sol is gelled in the same manner as in Example 1.

The center rod is pulled out and leaching is performed in the form shown in FIG. 2 while the wet gel state is maintained.

Leaching liquid 14 used ethyl alcohol.

FIG. 5 shows the correlation between the elapsed time and the ion density.

Here, 41 is silicon and 42 is titanium.

Wet gel that has been soaked for 5 hours is 50~7
Dry at a temperature of 0°C, dry gel (outer diameter 6W, inner diameter 2
．． , length 60 am), then placed in a deep air furnace, heated from room temperature at a rate of 600°C/H, and chlorine gas added at 1.5 t/H.
Hold for 2 hours while flowing M, and raise to 900℃ at the same temperature increase rate.
and held for 30 minutes while flowing dRfg gas at 117M. The temperature was further raised to 950° C. in the same manner, and held for 60 minutes while supplying 1 t/Mfi of helium gas to vitrify it.

FIG. 6 shows the refractive index values of various parts from the inner wall to the outer wall at this time.

Here, reference numeral 51 indicates an inner wall, and reference numeral 52 indicates an outer wall. When this glass was solidified and canned, a crated index type quartz fiber was obtained, and the transmission loss was 15 dB/.

In addition, when comparing the case where dry gel is prepared and vitrified using water as the leaching liquid and the case where ethyl alcohol is used, more cracks occur after vitrification when water is used (yield 50 %), almost no cracking occurred in the case of ethyl alcohol (yield: 98 cm). 0.5 mol) to
PH10 ammonia water 20%, ethyl alcohol 70%
Add the ingredients and stir and mix thoroughly to hydrolyze.

Furthermore, 50% of fine powdered silica (Aerosll-Ox50: a product name of Aerosil Co., Ltd. with a surface area of 50gf/f) was added. The sol is then gelled in the same manner as in Example 1.

The center rod is pulled out and leaching is performed in the form shown in FIG. 2 while the wet gel state is maintained.

As the leaching liquid 14, a solution of ethyl alcohol:water=3:1 was used.

At this time, the correlation between the elapsed time and ion production was approximately the same as in Example 2.

Wet glue that has been leached for 3 hours is 40 to 6
After drying at 0°C m degrees and forming a dry gel (outer casserole & 2ms+, inner diameter 2fi, length 6QQ-), it was placed in a saekiro furnace, heated at a rate of 50°C/H from room temperature to 600°C, and heated with chlorine. The temperature was maintained for 2 hours while flowing 2 t/M of gas, and the temperature was raised to 900° C. with the same 4-temperature change, and maintained for 30 minutes while flowing oxygen gas at 5 t/M. The temperature was further increased to 950° C. in the same manner, and the mixture was held for 30 minutes while flowing helium gas at 117M to vitrify it.

FIG. 7 shows the refractive index values of various parts from the inner wall to the outer wall at this time.

Here, 61 indicates an inner wall, and 62 indicates an outer wall.

Next, this glass was solidified and drawn to obtain a crated index type quartz fiber with a transmission loss of 1 hdn/Km.

2% When water is used as a leaching solution, cracks still occur after vitrification (steps?! ¥50), but when an alcohol aqueous solution is used, cracks are greatly reduced (yield: 97%). Nine.

[Example-4] Tetrainopropoxysilane 264F (1 mol), hexafluorosilicic acid 2882 (l 102 mol), 150% of a 11N salt was added, and the mixture was hydrolyzed by optical stirring and mixing. Sol.

This sol is poured into a cylindrical container to form a rod-shaped wet gel, which is then dried at a temperature of 50 to 70 C to form a dry gel (outer diameter 4.6 fi, length SO,).

Place the dry gel in a container containing isopropyl alcohol and perform leaching.

The correlation between gay ions and fluorine ions and elapsed time during leaching/& shows a tendency similar to tf in Example 1.

Dry gel that has been leached for 5 hours - day and night (1
7 hours) After drying at room temperature, it was placed in an electric furnace and heated at a rate of 30°C/H from the initial state to 600°C, and chlorine gas was added to the
．． While flowing 5 L/M, hold for 1 hour, raise the temperature to 900°C at the same temperature increase rate, and add oxygen gas to CL5t/M.
It was held for 30 minutes while flowing. The temperature was further raised to qsac in the same manner, and the mixture was held for 30 minutes while flowing helium gas at 117M to vitrify it.

FIG. 8 shows the values of the refractive index of each part from the center to the outer wall at this time.

Here, 72 indicates an outer wall.

Next, by drawing this glass, a crated index type quartz fiber is obtained, with a transmission loss of 10 dB.
/Km.

2. When using 9f of water as the leaching liquid, cracks still occur after vitrification (yield: 75%);
When alcohol was used, cracks were significantly reduced (yield: 98 cm).

〔Effect of the invention〕

As described above, according to the present invention, in the production of an optical fiber base material by the sol-gel method using silicon alkoxide as the main raw material, a tubular gel ( wet gel, dry gel,
By exploding a sintered gel and leaching the tubular gel using alcohol or an aqueous alcohol solution, elements that change the refractive index of the base material are eluted, resulting in a highly accurate refractive index distribution. , it becomes possible to manufacture optical fiber preforms at high manufacturing speed and at low cost.

In particular, by using alcohol or an aqueous alcohol solution after leaching, there are various advantages such as greatly improving the yield and expanding the conditions in the post-leaching process.

Furthermore, the method of the present invention applies not only to the optical fiber base material, but also to
It has the effect of being applicable to various types of optical components such as cell 7-year-old lenses.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a sol injection container in an embodiment of the present invention. W. Figure 2 is a conceptual diagram of leeching in an embodiment of the present invention. FIG. 3 is a correlation diagram between leaching treatment time and ion concentration in an example of the present invention. Figure WX4 is a refractive index distribution diagram of each part of the glass in an example of the present invention. FIG. 5 is a correlation diagram of leaching treatment time and ion concentration in another example 2 of the present invention. Figure 86 is a refractive index distribution diagram of each part of the glass in another embodiment of the present invention. FIG. 7 is a refractive index distribution diagram of each part of the glass in still another embodiment of the present invention. FIG. 8 is a refractive index distribution diagram of each part of the glass according to still another embodiment of the present invention. Applicants: Seiko Epson Corporation 4F Drama, 10 patent attorneys, 1 attorney, 11, 2nd cause + 41. ? (m, ) Distance of Kobo et al. No. 6 (4 02 feature <, --) Koshishiφ et al.'s distance 1 Fig. 7

Claims (1)

[Claims] In the production of optical fiber base materials using the sol-gel method, which uses silicon alkoxide as the main raw material, tubular gels (wet gels, dry gels, sintered gels) are created by adding elements that change the refractive index of the base material in advance. A method for producing an optical fiber base material, characterized in that the tubular gel is leached using alcohol or an alcohol aqueous solution.