JPS63190740A - Manufacture of halide glass optical fiber - 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 [Industrial Application Field] The present invention relates to the production of infrared-transparent optical fibers made of halide glass, especially heavy metal fluoride glasses, by drawing them from a ferrous material in a gas atmosphere. This relates to a manufacturing method.

[Prior art] For example, barium fluorozirconate (Ba
F! Infrared-transparent optical fibers made of heavy metal fluoride glasses based on ZrFa) or glasses based on beryllium fluoride will form the next generation of ultra-low-loss glass fibers for long-distance optical communications ( Literature (D, C, Tran, Conf, onOpt, F
iber Communication+ At1an
ta+ 1986, Techn, Digest 20
In order to be of practical use, this type of fiber must exhibit a corresponding strength, whereas halide glasses made from fluorides, chlorides, bromides or iodides are absorbs hydroxyl groups from
There is a tendency to react already at room temperature or at least at the fiber drawing temperature with the release of gaseous hydrogen halides. This reaction degrades fiber strength and increases optical fiber losses. Furthermore, in the case of halide glasses, which are extremely reactive towards HtO, even a nominally dry protective gas atmosphere with an H,O content of 1 to 1 oppm is
It has been proven that it is not suitable for fabricating fibers with H-free surfaces that exhibit high strength and good loss characteristics.

[Problem to be solved by the invention]

The purpose of this invention is to prevent harmful OH from halide glass.
Another object of the present invention is to provide a method for manufacturing an optical fiber made of halide glass without absorption or diffusion of water.

[Means to solve the problem]

This object is achieved by the manufacturing method characterized in claim 1.

(Function and effect) The drying effect in the manufacturing method of this invention is that the desiccant chemically reacts with moisture, chemically decomposes or converts the water vapor present in the gas atmosphere into a substance that does not contain OH, and at the same time It is based on chemically decomposing or converting the hydroxyl groups present at great depths so that OH is no longer present.

With this invention, for the first time, a process known in principle for the reactive drying of inorganic salts using moisture-reactive desiccants, such as acid chlorides, has been applied to the drawing of optical fibers.

[Embodiment] The desiccant used in the production method of this invention also includes acid chloride,
It is advantageous to choose from acid fluorides and acid anhydrides (claim 2).

This acid chloride is 5OCj! *, Soo, C1t and C
F3 Co(l) (Claim 3).

As acid fluorides, SOF, , So, F, , C0F
z, CF, and COF are preferred (claim 4).
section).

As the acid anhydride, trifluoroacetic anhydride is advantageous because it has particularly good adhesion to fiber coatings made of perfluoroethylene propylene or FEP (claim 5).
section).

For drying, it is also possible to use a desiccant that reacts with moisture only at a temperature above room temperature (Claim 6), unlike the above-mentioned desiccant.
, Cx Fh, Cs Fs, hexafluoropropylene C5Fh, octofluorocyclobutane C-Fs, hexafluoroacetone C,F, 01NFs, ClF5
, BrF5 , IF, , SF, , SF4 , chlorofluorocarbon or freon are preferred (Claim 7).

As the chlorofluorocarbon, for example, CC1tFt-CC
I;lt Fs, Ct Fs C1, etc. are suitable (
(Claim 8).

In order to remove the acid gas generated by the chemical reaction with the desiccant from the glass surface, it is advantageous to draw the fiber through an acid-neutralizing gas atmosphere after drawing it through a dry gas atmosphere (claim 9). (Claim 1O), it is advantageous for this acid-neutralizing gas atmosphere to contain NH (Claim 1O).

The glass material, which is advantageously used in the form of a preform, is predried in a gas atmosphere containing a moisture-sensitive desiccant before the fiber is drawn.

During the glass manufacturing process, water that has already entered the glass material, such as a preform, is dried by treating the fiber with a desiccant that reacts with moisture. The possibility of reduction is particularly valuable. Claim 12 is directed to this possibility, and the treatment of the fiber is
It is advantageous to use ocgt moqi (claim 13).

The above inventions are combined to form a single inventive idea of reducing or eliminating the residual influence of hydroxyl groups on optical glass by treating it with a moisture-responsive desiccant.

〔Example〕

The invention will be explained in more detail with reference to the drawings.

One embodiment of the invention will be described with reference to the fiber drawing apparatus shown in FIG. ZBLA glass rod preform 2
the lower end 21 of is softened in a heating furnace 3, for example in the form of a graphite ring;
From there the fiber 1 is drawn vertically downwards. The preform 2 and the furnace 3 are placed, for example, in a closed vessel 4 with an upper gas port 41 and a lower gas outlet 42 . An opening 53 is provided in the bottom of the container 4, through which the fiber 1 is drawn out.

Dry argon gas Ar containing a small amount of thionyl chloride 5OC2 as a desiccant that reacts with moisture is introduced from the gas port 41 and discharged from the gas outlet 42 below. Thereby, the preform 2 and the fiber 1 drawn out from it are surrounded by a drying gas atmosphere containing a desiccant that reacts with moisture.

A preform of ZBLA glass, etched in a manner known from DE 35 14 082 A1, was used and coated afterwards at 20° C. in the gas atmosphere of the apparatus of FIG. 1 before fiber drawing. F becomes
After covering with the EP tube, it is pre-dried at 80°C and then the fiber 1 is drawn out.

In the drawing process, 5OC1 of the gas atmosphere inside the container 4,
The introduced mixed gas components are adjusted so that the gas content is approximately 1100 pp. In this atmosphere, the fiber 1 is drawn out at a temperature of 400° C. in the furnace 3. For this purpose, for example, a drawing drum located below the container 4 is used. This drum is not shown in the drawings.

Figures 2 and 3 show the measured values of the tensile strength and attenuation of the fibers made by the above method and the fibers made by the known method.1 Curves I and ■ are for the fibers drawn by the above method. The curves ■ and ■ are for fibers drawn without a desiccant from a ZBLA preform etched by a known method, and the curves ■ and ■ are for fibers drawn without a desiccant from an untreated ZBLA preform. be. The fiber drawn by the method of the invention exhibits a significantly improved strength on average of 440 MPa and a significantly lower attenuation value of -60 dB/- than the fiber produced by the known method.

In connection with these experimental results, we would like to point out the fact that the smooth surface of a preform chemically polished by the method of DE 35 14 082 can be damaged during fiber drawing. It is presumed that this is because ZrO, which has a high melting point, is formed in the glass used there, which acts as a nucleus and crystallizes the glass surface layer, reducing the strength and light transmission properties of the fiber.

In addition to 5ocx and other acid chlorides, acid fluorides are also suitable for drying. As this acid fluoride, those listed in claim 4 are used.

As previously mentioned, trifluoroacetic anhydride is particularly advantageous as a desiccant in that it provides good adhesion to FEP mantles.

For drying, it is also possible to use a desiccant that reacts with moisture only at high temperatures.

The above method and the substances listed therein are not limited to ZBLA, but in principle all halide glasses can be used.

In order to remove the acidic gas generated during the conversion from the glass surface to 5 oct, the fiber is drawn out in a gas atmosphere containing a desiccant and then passed through a neutralized gas atmosphere containing NH. Now, a further container 5 with a gas inlet 51 and a gas outlet 52 is attached to the container 4, and the fiber 1 is drawn through this container 5 - by way of example, the bottom side of the container 4 with the opening 53 acts as a partition for the container 5. There is.

At the bottom of the container 5 there is an opening 54 through which the fiber 1 is drawn. Advantageously, the openings 53 and 54 are constructed as nozzle openings that prevent the exchange of gas between the containers 4 and 5 and between the container 5 and the outside world.

A neutralized gas NH, is introduced through the gas port 51 and is discharged through the gas outlet 52.

In order to subsequently remove the water that has already reached the preform during the glass manufacturing process and thereby reduce the OH band of 2.9μ steel measured in the fiber, the device shown schematically in Figure 4 is used. be able to. The fiber is introduced into a container 6 which is provided with an inlet 61 for the gaseous desiccant and an outlet 62 thereof. For drying, a gaseous desiccant, for example, 5 oz, is introduced from the inlet 61 to fill the inside of the container 6, and is applied to the fiber 10 placed therein, which is wound, for example. This gaseous desiccant is discharged from the outlet 62.
is discharged through. Container 6 as well as vessels 4 and 5 can be configured such that the gas or gas mixture introduced therein is circulated through the vessels.

The container 6 shown in FIG. 4 can be combined with the device shown in FIG. The Off(band) can be reduced on-line later for the fiber 1.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for drawing fibers in a dry gas atmosphere, and FIGS. 2 and 3 show measured values of tensile strength and attenuation of fibers made by the method of the present invention and the conventional method. FIG. 4 is a schematic diagram of an apparatus for implementing the method of reducing the OH band of a glass fiber. In Figure 1, 1
...glass fiber, 2...rod-shaped preform,
3... Heating furnace, 41 and 51... Gas inlet, 42 and 52... Gas outlet. 31 Urinary heel good MPa -a”

Claims (1)

[Claims] 1) A glass material in a gas atmosphere characterized in that either one or both of the fiber (1) and the glass material (2) are surrounded by a drying gas atmosphere containing a desiccant that reacts with moisture. A method of manufacturing an optical fiber made of halide glass by drawing it from a glass. 2) A method according to claim 1, characterized in that the desiccant is selected from acid chlorides, acid fluorides and acid anhydrides. 3) Acid chlorides are SOCl_2, SO_2Cl_2, CF
3. The method according to claim 2, characterized in that it is selected from among _3COCl. 4) Acid fluoride is SOF_2, SO_2F_2, COF
3. The method according to claim 2, characterized in that the COF is selected from COF_2, CF_3COF. 5) The method according to claim 2, wherein the acid anhydride is trifluoroacetic anhydride. 6) A method according to claim 1, characterized in that a desiccant is used which reacts with moisture only at a temperature higher than room temperature. 7) Desiccant is BF_3, C_2F_6, C_3F_8,
Propylene hexafluoride C_3F_6, cyclobutane octafluoride C_4F_3, acetone hexafluoride C_2F_6O,
NF_3, ClF_3, BrF_2, IF_5, SF_
7. A method according to claim 6, characterized in that it comprises some of the following: 4, SF_6 and a fluorocarbon salt. 8) Carbon chlorides are CCl_2F_2, CClF_3,
8. Process according to claim 7, characterized in that it is selected from among C_2F_5Cl. 9) The method according to claim 1, characterized in that the fiber is drawn out in a dry gas atmosphere and then drawn out in an acid-neutralizing gas atmosphere. 10) The method according to claim 8, wherein the acid-neutralizing gas atmosphere contains NH_3. 11) A method according to claim 1, characterized in that the glass material is predried before drawing the fiber in a gas atmosphere containing a desiccant that reacts with moisture. 12) Glass fibers produced by the method according to one of claims 1 to 10, characterized in that the fibers are dried by treatment with a gaseous drying agent that reacts with moisture. How to reduce OH band. 13) A method according to claim 12, characterized in that the fiber is treated with SOCl_2 vapor.