JPS60246234A - Manufacture of fluoride optical fiber - Google Patents

Abstract

PURPOSE:To obtain the titled optical fiber having uniform quality, long length and low transmission loss, easily, preventing the crystallization, by increasing the viscosity of a molten fluorinated glass by a specific treatment, and spinning the molten glass while applying a coating resin material to the circumference. CONSTITUTION:The molten core glass 1 in the pressurized crucible 3 for core and the molten clad glass 2 in the pressurized crucible 4 for clad are heated in the furnace 13 to keep the core and clad glass in molten state. The molten glass 1, 2 are pressurized with the compressed gas sent through the inlet ports 5, 6 of the compressed gas for core and clad, and are sent to the double nozzle 8 through the double pipe 7 for supplying the molten glass for core and clad. At the same time, the flow rate and the temperature of the refrigerant 19 are controlled by the refrigerant pump 17 and the refrigerant heater 18 to increase the viscosity of the glass by cooling the glass to a temperature near the deformation temperature. Separately, the coating resin material 20 heated by the extruder 14 and the coating resin heating furnace 15 is extruded through the coating resin nozzle 9, and the highly viscous core clad glass extruded through the nozzle 8 is coated with the coating resin material 20 and drawn to obtain the titled fiber 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to the h-horn method for producing fluoride optical fibers, and more specifically, the present invention relates to the production of fluoride optical fibers using the h-horn method. l
16 concerning a method for producing m-loss fluoride optical fiber;
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[Background of the invention]

Conventionally, in the production of fluoride optical fibers, the preform method in which a glass preform is drawn by zone heating and the crucible method in which a glass melt is drawn through a nozzle hole have been used to draw the fiber.

By the way, fluoride glass has a small tendency to vitrify, and tends to crystallize when the cooling rate during vitrification is slow, and also when the glass is heated and maintained at a temperature above the glass transition temperature. It has the property of progressing crystallization. For this reason, it is not possible to produce large glass matrix materials,
It was difficult to increase the length using the BRIFORM method.

On the other hand, in the crucible method, the glass is heated to a temperature higher than the melting point in order to suppress the progress of crystallization. The method is to supply the glass melt little by little to a drawing nozzle kept at a temperature close to the deformation temperature of the glass, cool it, increase the viscosity, and then draw the glass.

However, with the conventional crucible method, glass crystallization could not be completely suppressed, and a homogeneous optical fiber could not be manufactured. Therefore, the loss value is several thousand dB/lua.
It was difficult to reduce the loss further.

[Summary of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for easily manufacturing a homogeneous, long, and low-loss fluoride optical fiber.

To summarize the present invention, the method for manufacturing a fluoride optical fiber according to the present invention involves introducing a fluoride glass melt held in a melting point tool into a drawing nozzle portion maintained at a temperature close to the deformation temperature of the glass. In the method for manufacturing fluoride optical fiber, the fiber is cooled to make it highly viscous, and then drawn to form a fiber.
The method is characterized in that the highly viscous glass melt is drawn while being coated with a coating resin material.

According to the method for manufacturing a fluoride optical fiber according to the present invention,
Since the neck down of the glass is formed in the softened coating resin during drawing, no ltj eruption of the glass constituents occurs, and surface crystallization is prevented, resulting in a homogeneous and m
This method has the advantage that it is possible to manufacture a fluoride optical fiber that is J-type and has low loss.

[Specific description of the invention]

The present invention will be explained in more detail.

According to the method for manufacturing a fluoride optical fiber according to the present invention,
The fluoride glass melt held in the melting point tool 2 is introduced into a wire drawing nozzle kept at a temperature close to the deformation temperature of the glass, cooled and made highly viscous, and then drawn to form a fiber. The highly viscous glass melt is coated with a resin material to be subjected to ri to be drawn and made into a fiber. 4", and any resin that does not evaporate the glass constituents from the surface may be used. For example, 47-fluorinated ethylene-6-fluorinated propylene co-merger (Teflon FEP), 47-fluorinated ethylene - Fluorine resins such as ethylene copolymer and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer can be used.

In this way, the coating resin material is coated on the glass melt during wire drawing, and by coating the glass melt with the coating material in this way, the glass pores are formed in the softened coating resin. Therefore, volatilization of glass constituents from the neck-down surface does not occur, and crystallization of the surface can be prevented. Therefore, compared to the conventional method in which the neckdown is formed in a glass atmosphere, the homogeneity of the optical fiber is significantly improved, and a low-loss optical fiber can be easily manufactured.

Further, when using a glass melt having a glass composition with a small glass tendency, a high cooling rate is required. In this case, before the glass melt, which has been cooled and has become highly viscous, is coated with a resin coating material and drawn into fibers, the glass melt is exposed to a closed space pressurized to 1 atmosphere or more. By making the temperature gradient steeper, it becomes possible to manufacture a good fluoride optical fiber. Since the space is maintained at less than 1 atm, volatilization of the glass constituents from the surface of the melt can be prevented. Therefore, a homogeneous, low-loss optical fiber can be easily obtained even with a glass composition that has a small tendency to vitrify. As the atmosphere glass here, dry inert gas, dry HF gas, dry F2 gas, etc. can be suitably used.

Next, an apparatus for carrying out the method of manufacturing a fluoride optical fiber of the present invention will be described.

FIG. 1 is a schematic diagram of an apparatus for carrying out the method of the present invention, in which 1 is a core glass melt, 2 is a cry I□
3 is a pressurized crucible for the core, 4 is a pressurized crucible for the cladding, 5 is a pressurized gas supply port for the core, 6 is a pressurized gas supply for the cladding. Melt supply double pipe, 8 is a single nozzle, 9 is a coating resin nozzle LIO is a heat insulating wall, 11 is a fiber, 12 is a fiber winding bobbin, 13 is a core/taranod glass melting furnace, 14 is a coating resin extrusion 15 is a coated resin heating furnace, 16 is a refrigerant cooler, 17 is a refrigerant transport pump, 18 is a refrigerant heater, 19 is a refrigerant, and 20 is a coated resin material.

As is clear from FIG. 1, the apparatus for carrying out the method of the present invention includes a pressurized core crucible 3 for storing the core glass melt 1 and the crat glass melt 2.
The pressurized crucible 3 for the core and the pressurized crucible 4 for the cladding are pressurized by pressurized gas from the pressurized gas supply port for the core and the pressurized gas supply port 6 for the cladding, respectively. It's starting to come under pressure.

The core glass melt 1 and the crat glass melt 2 are supplied to the core/talanod glass melt supply double pipe 7 having a double pipe structure by the pressurized gas from the pressurized gas supply port 5.6. It reaches the double nozzle opening 8 through the. A coating resin nozzle port 9 for coating the glass melt is provided downstream of this double nozzle port 8, and this coating resin nozzle port 9 opens into a space defined by a heat insulating wall 10. 1.This coating resin nozzle port 9
The discharged fiber 11 is wound onto a fiber winding bobbin 12.

The glass melt 1 for the core and the glass melt 2 for the flano (
is maintained in a molten state by a core/crat glass melting furnace 13.

The coating resin extruder 14 is in communication with the coating resin nozzle] 19, and extrudes the coating resin material 20 heated and softened in the coating resin heating furnace 15 in the direction of the coating resin nozzle opening 9, and extrudes the coating resin material 20 into the coating resin nozzle opening [18J]. The high-viscosity glass melt discharged is coated at the coating resin nozzle port 9.

Further, a cooling device section for cooling the double nozzle opening 8 is provided around the double nozzle opening 8,
This cooling device section includes a refrigerant cooler 16 and a refrigerant transport pump 17.
and a refrigerant heating v&18, and the nozzle ll-18 can be cooled by circulating the refrigerant 19.

In such an apparatus, in order to manufacture a fluoride optical fiber, the flow rate and temperature of the refrigerant 19 are adjusted by the refrigerant transport pump 17 and the refrigerant heater 18, and the tip of the core/cladding glass melt supply double pipe 7 is heated. While maintaining the portion near the deformation temperature of the glass, the coating resin material 20 is heated by the extruder 14 and the coating resin heating furnace 15, and the softened coating resin material 20 is extruded from the coating resin nozzle port 9.

On the other hand, the core pressure crucible 3 and the cladding pressure crucible 4
The core glass melt 1 and the Taranod glass melt 4 inside are heated by the core/Taranodo glass melting furnace 13 so as to maintain their molten state. Through the pressurized gas supply port 5 for the core and the pressurized gas supply port 6 for the cladding, the surfaces of the core gas melt 1 and the cladding glass melt 2 are pressurized, and they are fed into the core/cladding glass melt supply system. It is extruded from a double nozzle 8 through a pipe 7.

At this time, at the tip of the core/crat glass supply double pipe 7, the core/crat glass melt is cooled to near the glass deformation temperature and becomes highly viscous.

This highly viscous core taranod glass is pulled downstream from the double nozzle port 8 and the coating resin nozzle port 9 together with the softened coating material 20 to form a kudown in the softened coating resin, and a line is drawn. Make it into fiber.

FIG. 2 is a schematic diagram of another apparatus for carrying out the method of the invention, in which the same reference numerals as in FIG. 1 indicate similar parts. Further, 21 is a gas-tight container, 22 is a cock, and 23 is a double nozzle.

In this device, a gas-tight container 21 is provided between the double bisif and the one-ichi nostle 23, and the core thalassoto gas melt is exposed to the space formed by the sealed container 21. The hermetic container 21 is maintained at a pressure of 1 atm or more, and this pressure is higher than the 1 atm.
Set between the pressures applied to 16.

By adopting such a structure, the temperature gradient can be made steeper, and since the melt is exposed in the closed container 21 which is pressurized above the lukewarm air, the gas constituents can volatilize from the surface of the melt. It has the advantage of being worry-free.

Therefore, a homogeneous, low-loss optical fiber can be easily obtained even with a glass composition that has a small tendency to vitrify.

Next, examples will be explained.

Example 1 Using the apparatus for carrying out the method of the present invention shown in FIG. 2 4G
dF3-6AIF3 (mol%), fluoride optical fiber whose coating resin material is Teflon FEP (core diameter 50
μm, outer diameter 300. c+m, '41! aResin thickness 50
It was manufactured under the following conditions with a length of 5 μm, a length of 5 +++, and a loss of 20 dB/km (wavelength: 2.4 μm).

Core glass melt furnace temperature 900°C Core glass melt pressurized gas pressure 1, 02a tm Clad glass melt pressurized gas pressure 1.02 atm111) Dual nozzle opening rz 1.2 to 3 Nozzle nozzle for coating resin Diameter 5 amφ Coated resin heating furnace temperature 360°C Coated resin extrusion speed ice/min Refrigerant temperature 320°C Refrigerant flow 1 1.512/ll1in Drawing speed 20 m/win Example 2 The method of the present invention shown in FIG. Using the equipment for the implementation, the glass for the core was 50ZrF 4-20BaF 2-
4GdF3-3AIF3 (mol%) glass, cladding glass is 50ZrF 4-20BaFe -4Gd
P 3 6AIF 3-201. iF (mol%),
Fluoride optical fiber whose coating resin material is Teflon FEP (217 diameter 5011 m, outer f! 300 μm,
Covered V32 resin thickness 50/71+1, Ji; length 5km,
A loss of 30 dB/km (wavelength: 2.4 μm) was produced under the conditions described in F.

Core Taranod glass melt furnace temperature 900'c Coco glass melt pressurized gas pressure 1, 04a tm Clad glass melt pressurized gas pressure 1.04 atm Double nozzle diameter 1
．． 2~3m11φ Gas sealed container pressure ], 02 atm Coating resin nozzle diameter 5 msφ Coating resin heating furnace temperature 300℃ Coating resin extrusion speed lee/min Refrigerant temperature 260℃ Refrigerant flow rate 1.54! /min Drawing speed: 20 m/min [Effects of the Invention] As explained above, according to the method for manufacturing a fluoride optical fiber according to the present invention, a long, low-loss fluoride optical fiber can be easily manufactured. This has the advantage that optical communication using infrared light with a wavelength of 1 to 3 μm becomes possible.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an apparatus for carrying out the dipping method for manufacturing a fluoride optical fiber according to the present invention (13) (12); 1 is a schematic diagram of another apparatus. 1... Melt for core, 2... Gas melt for cladding, 3... Pressurized crucible for core, 4... Pressurized crucible for cladding, 5 ... Pressurized gas supply port for core, 6
... Pressurized gas supply for cladding [1, 7 ... Core / taranod gas melt supply double pipe, 8 ... Double nozzle port, 9 ... Nozzle port for coating resin, 10 ... Heat insulation Wall, 11... Fiber, 12... Fiber winding bobbin, 13... Core/cladding gas melting furnace, 14...
・Coated resin extruder, 15...Coated resin heating furnace, 16.
... Refrigerant cooler, 17... Refrigerant transport pump, 18...
- Refrigerant heating machine, 19... Refrigerant, 20... Covering resin material, 21... Airtight container. Applicant's agent Masaki Amemiya (14)

Claims (1)

[Claims] (A fluoride glass melt maintained at a melting point of 1.1 or higher is introduced into a nozzle section maintained at a temperature near the deformation temperature of the glass, cooled, and made highly viscous, and then drawn into a line. A method for manufacturing a fluoride optical fiber to be made into a fiber, which comprises drawing the glass melt that has been cooled and made highly viscous while covering it with a coating resin material. (2) The cooling. The fluoride optical fiber according to claim 1, wherein the glass melt is exposed to a closed space maintained at a pressure of 1 atmosphere or more and then guided to the nozzle portion. manufacturing method.