JPS6296337A - Production of optical fiber preform - Google Patents

Abstract

PURPOSE:To uniformize drying of an optical fiber preform in the production of the preform by sol-gel process, to eliminate the deformation of the preform and to improve the yield, by drying a wet gel under rotation. CONSTITUTION:In the production of an optical fiber preform by sol-gel process, a wet gel 1 is put into a drying vessel 5 and dried under rotation with rollers 4. The drying can be uniformized by this process, the yield can be improved and the warpage of the product is minimized. Since gravitational force is uni formly applied along radial direction, an optical fiber preform having improved roundness and high quality can be produced at a low cost.

Description

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

[Summary of the invention]

The present invention is a method for manufacturing a base material for Hikari 7 eyewear using a sol-gel method, in which wet gel is dried while being rotated, thereby making drying uniform, improving yield, and reducing warpage. In addition, gravity is applied evenly in the direction of the finish, and roundness is improved. Furthermore, since the drying speed can be increased, even if the drying period is significantly shortened, the dryness can be significantly improved.

[Conventional technology]

In the conventional sol-gel method for manufacturing an optical fiber preform, tubular or cylindrical gel is dried by placing wet gel in a drying container and leaving it at a predetermined temperature.

[Problem that the invention seeks to solve]

However, with the above-mentioned conventional technology, during gel drying, the area where the gel is placed in the drying container dries more slowly than other areas, resulting in uneven drying and the gel may be printed during drying. , it may warp.

In addition, due to the uneven spatial distribution of the vapor pressure of water and alcohol in the drying container, the drying of the gel becomes uneven, resulting in uneven gel drying, which may cause printing during gel drying. It may warp. Furthermore, if the gel is dried with its axis horizontal, the water or alcohol contained in the gel will come into contact with the lower part of the gel, causing it to warp. i! If the drying speed is reduced by, for example, reducing the opening ratio of the drying container in order to prevent the drying process, the drying process will take a long period of time, and mass productivity will be significantly deteriorated, making it impractical. Furthermore, the gel is still soft in the early stages of drying, so
It deforms due to gravity. Therefore, unless the gel is dried with its axis vertical, the roundness of the resulting gel will be poor. If the gel is dried with its axis vertical, this problem does not occur, but a long gel will collapse under its own weight, making it impossible to make a long, large optical fiber preform.

Therefore, the present invention aims to solve these problems all at once.The purpose of the present invention is to dry the gel uniformly and quickly without deformation, and with a good yield, and to produce a high-quality optical fiber matrix. The present invention provides a method for manufacturing an optical fiber preform in which a material with good tffl properties can be obtained. The method for manufacturing an optical fiber preform by the method is characterized in that the wet gel is dried while being rotated.

[Effect]

By drying the gel while rotating it around the axis, the outer periphery of the gel comes into even contact with the drying container, which eliminates uneven drying and prevents the gel from cracking or warping during drying. . Also, in the drying container,
Even if there is non-uniformity in the vapor pressure distribution of water or alcohol, it can be ignored, non-uniformity in drying is eliminated, and the gel does not crack or warp during drying. In addition, the water and alcohol contained in the gel no longer accumulate at the bottom of the container and come into contact with the gel, which prevents the gel from cracking or warping during drying. In this way, even if the drying speed is increased, the gel will not crack or warp during drying. Furthermore, since gravity is applied evenly in the radial direction of the gel, the roundness of the resulting gel will not deteriorate.

As described above, according to the present invention, the gel can be dried uniformly and with a high yield without deforming the gel.

This will be explained in detail below using examples.

[Example 1] Add 0.02N hydrochloric acid 475, Of to ethyl/Licade 686.4P and stir well to prepare hydrolyzed m for cladding.
It was made into a liquid.

ethyl chloride) 159.6r [L2 normal hydrochloric acid 22
-3F was added and reacted with vigorous stirring. When the solution became clear, tetraethoxy7 germanium 1 & 9
2 was added little by little and stirred well.

After reacting for 50 minutes, 02N salt # was added to the reaction solution.
57.1 F was added and reacted, and further 594 tons of water was added and stirred well to obtain a hydrolyzed solution for the core.

In addition, during the process of making the hydrolyzed solution for the core, the reaction solution was 10C.
Please keep the following in mind.

Next, ethyl 7 liquefaction) 104a7F, anhydrous ethanol 1527F, 29% ammonia water 25.9F, water 5
62.8f were mixed and stirred vigorously for 2 hours, and then kept in a cool, dark place overnight, and the solution containing 7 Lilifine particles was combined.

After concentrating this melt under reduced pressure, the alcohol content in the solution was replaced with water. Thereafter, the PM value was adjusted to 4.0 using diluted hydrochloric acid, followed by filtration using a 1.0 μm membrane filter to obtain a silica fine particle dispersion solution having an average particle size of IIL 18 μm.

Next, four-fifths of the hydrolyzed solution for cladding and the silica fine particle dispersion solution were mixed, [12] The pH value was adjusted to 4.69 using aqueous ammonia and water, and the volume was adjusted to 2000.
This was adjusted to mt and used as a sol solution for cladding.

In addition, one-fifth of the hydrolyzed solution for the core and the 7-liquid particle dispersion solution were mixed, and the pH value was adjusted to 4.46 using the ammonia water and water specified in Q.2. It was adjusted to 500 mt and used as a core sol solution. At this time, the temperature of the core sol solution was kept at 150° C. or less.

This is because if it exceeds 150, the gelation time becomes too soft, which is disadvantageous in terms of operation.

Furthermore, all the raw materials used in the process are distilled, filtered, etc., and all processes are cleanliness class 100 ((
Next, the sol solution for crand was transferred to a cylindrical rotating container (diameter: 50 mm, length: 1020 m+, circular volume: 1963 ml). This cylindrical rotating container 61ζ was covered with a lid and attached to a rotating device, and was gelled while rotating at 1500 rpm. After that, the sol bath solution for the core was transferred to the center hole created after gelation, and it was gelled. The outer diameter was 50mm and the length was 10004mm.
A cylindrical wet gel with a core portion having an outer diameter of 20B was obtained.

Four cylindrical wet gels made in the same manner were transferred to a drying container as shown in Fig. 1, the opening ratio was set to LL2%, and the gel was dried at 60C while rotating at a rotation speed of 1 rpm. Outer diameter 3511, length 662' in 19 days
Four pieces of dry gel with a core outer diameter of 1.52 mm were obtained. The dry gel has a warpage of Q and a roundness of 5.0μ.
m, and compared to conventional dry gel that was dried without rotation, both warpage and perfect circular support were improved by more than an order of magnitude.

When the obtained dry gel was sintered under the sintering conditions shown below, a base material for Hikari 7 Eyepa which was transparent and vitrified and had an integrated core land was obtained.

A single-mode optical fiber was obtained by placing the light-collecting fiber preform into a quartz-type jacket tube, fusing it, and drawing it.

The conduction loss of the obtained original fiber was 1.0d at 1.3μm.
It was confirmed that it was less than B/Km and was a loss.

[Sintering conditions]

Place the dry gel in a quartz tubular furnace and heat up at a rate of 50C/hr.
The sample was heated from 30C to 200C and held at this Ia+[ for 5 hours, then heated from 2DC to 3000C at a temperature increase rate of 50c/hr, and held at this temperature for 5 hours to perform desorption water. Continue to 300 at a heating rate of 30C/hr.
C to 920 C and held at this temperature for 30 minutes to perform decarburization, dechlorination ammonium treatment, and dehydration comprehensive reaction acceleration treatment. Next, He 2t/mins
C@Q, the temperature was maintained at that temperature for 1 hour while flowing a mixed gas of 2 t/min, the temperature was raised from 920 C to 10 aC, and the temperature was maintained at 1000 C for 2 hours to perform OH group removal treatment. Followed by 0. was heated to 1100C at a temperature increase rate of K 60 C/hr at IL/1 nL, and held at that temperature for 20 hours to perform desalination treatment. Next, while flowing only H., the temperature was increased at a rate of 50C/hr for 12
The temperature was maintained at 50C/>oML for 1 hour to perform pore-closing treatment.

Next, the sample was heated to 1400C at a heating rate of 60C/hr.
When the glass was heated to a temperature of 30 minutes and held for 30 minutes at one time, it became non-porous and became transparent glass.

[Run 2] Ethyl silicate 185α6F, absolute ethanol 231
6f', 29% ammonia water 7α5? , water 6532 were mixed, stirred vigorously for 2 hours, and aged in a cool dark place.
Nine force particles were grown. After concentrating this solution under reduced pressure,
In order to increase the drying process, the alcohol content of #condensed liquid was partially replaced with water. After that, the pH value was adjusted to 4.0 using two-dimensional hydrochloric acid to prevent rapid gelation when mixed with the hydrolyzed solution, and then filtered using a 160 μm membrane filter to average the Particle size Q, 28
A dispersion m solution of μm-sized Solica particles was prepared and used as a first solution.

Ethyl/Licade 122CL3F with α02 change salt 11
fi844? was added and hydrolyzed with vigorous stirring to obtain a second solution.

Next, mix this solution with the first #1 solution, and then (L2
Adjust the pH value to 4.85 using specified ammonia water and water.
Adjust the volume to 4000 mt, and add sol
@g, I made it.

The sol solution was poured into 8 cylindrical vessels (inner diameter: 40 mm, height: 550 mm).
■) After transferring it to a depth of 500■, 50t
After degassing with orr for 2 minutes, the container was sealed with a lid. Gelation started 40 minutes after the pH adjustment, and a cylindrical wet gel was obtained.

Next, the gel was transferred to the same drying container as shown in Figure 1, and the open area on the drying container was set to Q, 2%, and dried at 60C while rotating at the rotation speed shown in Table 1. As a result, a dry gel with an outer diameter of 27.0 m and a length of 357 m was obtained in 17 days. Furthermore, regarding each condition of the first commandment, 60
Each book was created under the same conditions.

From Table 1, average values of the dry gel obtained for warpage and roundness, the samples dried with rotation showed a higher yield, warpage and roundness than the samples dried without rotation. It can be seen that there is a clear improvement in both cases. The rotation speed is α0
It can be seen that both a relatively slow rotation speed of 1 rpm and a relatively high rotation speed of 1100 rpm are sufficiently effective.

When the obtained dried 4& was sintered under the sintering conditions shown below, the outer diameter was 1 a 41P11 and the length was 25
A transparent quartz rondo of No. 01 was obtained, but by tufting the pure quartz rondo and using a fluoropolymer as the cladding, the core diameter was 200 μm1 and the cladding diameter was 500 μm.
A μm optical fiber was obtained.

The conduction loss of the obtained optical fiber was (428 at L85 μm)
/Km or less, and it was confirmed that it could be used sufficiently as an optical fiber for I and AN.

[Sintering conditions]

Place the dry gel in a quartz tubular furnace and heat up at a rate of 30C/hr.
heated from 30C to 200C at a heating rate of 30C/hr, held at this temperature for 5 hours, and then heated from 200C to 3C at a heating rate of 30C/hr.
It was heated to 00C and held at this temperature for 5 hours to perform desorption of water. Continue to 300c at a heating rate of 130c/hr.
to 920C and held at this temperature for 50 minutes to perform decarburization, dechlorination ammonium treatment, and dehydration comprehensive reaction acceleration treatment. Next, He 2t/min,
Ce (lL2t/m In) was maintained at that temperature for 1 hour while flowing a mixed gas of 920C to 1000C.
The temperature was raised to 1000° C. and held at 1000° C. for 2 hours to remove OH groups. Followed by 0. The temperature was raised to 1100 (1:1) at a heating rate of 60 C/hr while flowing It/min, and the temperature was held at that temperature for 20 hours to perform desalination treatment.Then, the temperature was raised while flowing only H. 12 at speed 30C/hr
It was heated to 50° C. and held at this temperature for 1 hour to perform a pore-closing treatment.

Subsequently, the sample was heated to 1400C at a temperature increase rate of 60C/hr, and when held at this temperature for 30 minutes, it became non-porous and became transparent glass.

[Example 5] Ethyl silicate 185Q, 6f1 absolute ethanol 25
16f, 29% ammonia water 7Q, 5f, water 6352
After stirring vigorously for 2 hours, the mixture was aged in a cool and dark place to grow fine silica particles. After concentrating this solution under reduced pressure, the alcohol content of the A4 liquid was partially replaced with water in order to increase the amount of residue in the drying process. After that, the pH value was adjusted to 4.0 using 2N hydrochloric acid to prevent rapid gelation when the hydrolysis solution was mixed, and then further adjusted to 1.0.
Filtered using a μm membrane filter and average particle size Q
, prepare a dispersion solution of 28 μm silica fine particles, and run the first solution.

Ethyl silicate 122 [13F [L02 standard hydrochloric acid 844? was added and hydrolyzed with vigorous stirring to obtain a second solution.

Next, the first solution was mixed with the first solution for this m night, and then (the pH value was adjusted to 4.85 using L2 standard ammonia water and water, and the body injection was adjusted to 4000 mt to create a sol solution. did.

The sol solution was transferred to a cylindrical rotating container (circle diameter: 40 + lll: 11, length: 520. Obtained. The gel was then transferred to the same drying container as shown in FIG.
When drying was carried out at 600°C under the conditions shown in Table 2, the outer diameter was 27.01151. A dry gel with an inner diameter of 135 fi and a length of 557 m was obtained.

In addition, 60 tubes were produced under the same conditions under each condition shown in Table 2.

Table 2 From Table 2, it can be seen that the yield of the sample dried while rotating was clearly improved compared to the sample dried without rotating. Moreover, it can be seen that the faster the drying rate, the more remarkable the improvement. Therefore, it can be seen that the period required for drying can be significantly shortened by drying while rotating. When the obtained dry gel was sintered with the sintering flexibility shown below, a transparent pure quartz tube with an outer diameter of 1 a4 m, an inner diameter of 221 cm, and a length of 230 cm was obtained. By using as a clamp, the core diameter is 200
An optical fiber with a cladding diameter of 30 pm was obtained.

The transmission velocity loss of the obtained optical fiber was 4.1 at 0.85 μm.
It was confirmed that the B/KI was 11 or less, and that it could be sufficiently used as an optical fiber for LAN.

[Sintering conditions]

Place the dry gel in a quartz tubular furnace and heat up at a rate of 50C/h.
The sample was heated from SaC to 2000℃ at r, held at this temperature for 5 hours, then heated from 2QOC to 3000℃ at a heating rate of 30C/hr, and held at this temperature for 5 hours to perform desorption water. Next, at a heating rate of 30C/hr,
The material was heated from 0C to 920C and maintained at this temperature for 50 minutes to perform decarburization, dechlorination ammonium treatment, and dehydration comprehensive reaction treatment. Rizite H @ 2 L/m
i n, Ci[L2. The temperature was maintained at that temperature for 1 hour while flowing a mixed gas of Llrn 1 m, then the temperature was raised from 920°C to 1000C, and the temperature was maintained at 1000C for 2 hours to perform OH group removal treatment. Followed by 0. The temperature was raised to 1100C at a temperature increase rate of 60C/hr while flowing It/min, and the temperature was maintained for 20 hours to perform a desalination treatment. Next, the heating rate was 130c/h while flowing only ■.
It was heated to 1250C at r and held at this temperature for 1 hour to perform pore-closing treatment.

Subsequently, the sample was heated to 1400C at a heating rate of 6 DC/hr, and when held at this temperature for 50 minutes, it became non-porous and became transparent glass.

Although the method for manufacturing the optical fiber preform of the present invention has been explained using the three examples above, it is not limited to the pure quartz rond, tube, and single mode optical fiber preform of the present example; It is clear that the method can also be applied to manufacturing other than the cross-section of .

〔effect〕

As described above, according to the present invention, since the tubular or cylindrical gel is dried while being rotated around its axis, drying becomes uniform, yield is improved, and warping is reduced. Also, since gravity is applied evenly in the radial direction, roundness is improved. Furthermore, since the drying speed can be increased, the drying period can be significantly shortened and mass productivity can be improved. Therefore, we believe that the present invention is an indispensable technology for providing high-quality optical fiber preforms at low cost.

[Brief explanation of drawings] 1st I5! J is a sectional view of a drying container showing one embodiment of the present invention. 1... Gel 21... Core part 3... Crut part 4... Roller 5 which rotates in conjunction with...
・Drying container. that's all

Claims (1)

[Claims] 1. A method for producing an optical fiber preform by a sol-gel method, which comprises drying the wet gel while rotating it.