JPS6374939A - Production of fluoride fiber with coated layer and device therefor - Google Patents

Abstract

PURPOSE:To form a coated layer without reducing transmission characteristics and strength, by drawing core glass consisting of fluoride glass and fiber consisting of clad glass, extruding a coating material and applying the material to the surface of the fiber. CONSTITUTION:Core glass 13 and clad glass 14 are melted in a crucible 12 arranged in a container 16 in an inert gas or a fluorine gas atmosphere by an electric furnace 22. The molten glass 13 and the molten glass 14 are fed through feed pipes 25 to double crucibles 27 and 28 having concentrically formed nozzles. Core glass 29 and clad glass 30 in the crucibles 27 and 28 are adjusted to drawing temperature by a heater 33 and drawn into fiber 40 by a capstan 10. Simultaneously, a coating material 32 in a container 31 with a nozzle concentrically set at the outer periphery of the double crucibles 27 and 28 is extruded by high-pressure gas and is stuck fast to the surface of the fiber 40. Consequently, a three layer structure of the core glass 29, the clad glass and the coating material 32 is formed at the same time to give a fluoride glass fiber with the coated layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method and apparatus for producing a coated fluoride glass fiber with low loss, long length, and high mechanical strength by a crucible drawing method.

(Prior art and its problems) Fluoride glass fiber has a minimum loss of 0.
．． 001 dB/km, and is attracting attention as a transmission line for international long-distance optical submarine cables and non-repeater optical transmission systems. When using fluoride glass fiber as such a long-distance transmission line, at least t
It is necessary to continuously produce fluoride glass fibers of AB or higher. The crucible method has attracted attention as a method for producing long fluoride glass fibers, but due to the instability of the glass, it has been difficult to form a core-clad structure and it has not been realized. However, recently, 53Zr has been added to the core glass.
-20Ba-2ONa -4La -3At, 39.7Zr on clad glass -13,3Hf -18Ba-
By using 22Na-4La-3AI, it was shown that fluoride glass fibers can be produced using the crucible method (Elect, Let tersN
OV, 1985. Vol, 21. NO, 24). In order to apply the 77-hide glass fiber to an actual transmission line, it is necessary to form a coating layer to protect the fiber surface and increase the fiber strength.

Thermosetting or ultraviolet curable resin is used as a coating layer for conventional optical fibers.

Fig. 1 shows a conventional method of forming a coating layer in the crucible drawing method, in which 1 is a core glass, 2 is a clad glass, 3 is a crucible for core glass, 4 is a crucible for clad glass, and 5 is a crucible for clad glass. An electric furnace for heating a crucible for glass melting, 6 a fiber wire diameter monitor, 7 a coating container for coating with resin, 8 a coating material (coating resin), 9 a furnace for curing the coating resin, 10 a cap for fiber drawing. 11 is a fiber winding drum, and 40 is a drawn fiber.

The procedure for forming a coating layer using this device is as follows:
The core glass 1 and the cladding glass 2 are heated to the drawing temperature using the electric furnace 5, the fiber diameter is measured using the fiber diameter monitor 6, and drawing is started while adjusting the rotation speed of the capstan 10 so that the fiber diameter is constant. do. After the fiber diameter has been drawn to a desired constant thickness, the coating container 7 is placed in a predetermined position, the coating resin 8 is injected, and the fiber is drawn through a small diameter hole at the bottom of the coating container 7. It is applied thinly to the fiber 40 where it passes through, and is cured in the curing furnace 9 to form a coating layer.

When this method is applied to the formation of a coating layer for fluoride glass fibers, fluoride glass has extremely high reactivity compared to conventional oxide glasses (silica glass, multi-component glass, etc.) When the glass (meniscus) of the fiber comes into direct contact with the atmosphere, it reacts with oxygen and moisture in the atmosphere, causing a crystalline phase to precipitate on the fiber surface, increasing loss and reducing strength. Therefore, when producing a fluoride glass fiber, it is necessary to create a completely inert atmosphere around the glass which is in a high temperature state. However, since the fiber 40 is continuous from the crucibles 3 and 4 to the winding device 11,
It is extremely difficult to maintain only the meniscus portion in an inert atmosphere, and it has been difficult to apply conventional methods for forming a coating layer for optical fibers to forming a coating layer for fluoride glass fibers.

Therefore, a manufacturing method and manufacturing apparatus that can form a coating layer on a long fluoride glass fiber without reducing the transmission characteristics and strength of the fiber has been strongly desired. Nothing had been suggested.

(Objects and Features of the Invention) The present invention was made to solve the problems of the prior art described above, and it is possible to coat a long fluoride glass fiber without reducing the transmission characteristics and strength of the fiber. An object of the present invention is to provide a method and apparatus for manufacturing a fluoride glass fiber with a coating layer that can form a layer.

A feature of the present invention is that the fluoride glass has a three-layer structure of the core glass, the clad glass, and the coating layer, while the inside of the glass melting part and the inside of the wire drawing part for melting the core glass and clad glass are kept from direct contact with the atmosphere. The goal is to form fibers all at once. As a result, the coating layer is formed without the core glass and the cladding glass reacting with oxygen or water in the atmosphere, making it possible to prevent deterioration of the transmission characteristics of the fiber.

(Structure of the Invention) The method of the present invention includes a first step of melting a core glass made of fluoride glass and a clad glass in an inert gas or fluorine gas atmosphere, and a second step of melting the molten core glass and clad glass. A second step of adjusting the temperature of the coating material so that it does not decompose at the drawing temperature and has a viscosity equal to or lower than the viscosity of the core glass and clad glass. , and a third step of simultaneously forming a three-layer structure of core glass, cladding glass, and coating material.

Further, the apparatus of the present invention provides a glass melting section having a first heating means for melting a core glass made of fluoride glass and a clad glass, and a first gas introduction means for creating an inert gas or fluorine gas atmosphere. a double crucible with a nozzle, the nozzle of which is formed concentrically, and which accommodates the core glass and clad glass that are molten in the glass melting zone; and the nozzle is concentrically formed around the outer periphery of the double crucible. a container with a nozzle for coating material; at least one second heating means for adjusting the core and clad glass in the double crucible and the coating material in the container to a desired temperature; - an inert gas atmosphere; A three-layer structure of the core glass, the clad glass, and the coating material drawn out from the drawing section is simultaneously formed, and the fluoride glass fiber with the coating layer is drawn out. and a winding section for winding up the winding device.

(Example) The present invention will be described in detail below using the drawings.

FIG. 2 is a schematic diagram of the apparatus for manufacturing a fluoride glass fiber with a coating layer according to the present invention, which is composed of approximately three parts: a glass melting section A, a drawing section B, and a winding section C. The structure of the winding section C is the same as the conventional example shown in FIG.
Therefore, in the following description, the glass melting section A and the wire drawing section B, which are the characteristics of the present invention, will be described in detail.

First, the glass melting section A includes a glass melting crucible 12 for melting fluoride glass, a core glass 13 in a molten state, a clad glass 14 in a molten state, a jig 15 for holding the crucible 12, and a glass melting crucible 12 for melting fluoride glass. a container 16 for maintaining the atmosphere of the glasses 13 and 14 in an inert gas atmosphere; a lid 17 for the container; a container 16 and a lid 17 for the container;
a puffing 18 for maintaining airtightness with the molten glass 13, a gas inlet 19 serving as a first gas introduction means for creating an inert gas or fluorine gas atmosphere around the molten glass 13, 14; Consisting of a gas outlet 20 associated with the introduction means, an inert gas introduction port 21 for extruding the molten glass 13.14, and an electric furnace 22 that is the first heating means for melting the glass 13.14. has been done.

Next, the wire drawing section B includes a gas introduction port 23, which is a second gas introduction means for creating an inert gas atmosphere inside the container 16;
a gas outlet 24 also associated with the second gas introduction means;
Pipe 25 for injecting glass 13, 14 from glass melting section A to drawing section B, glass melting section A and drawing section B
a backing 26 for maintaining airtightness with the core glass, a nozzle-equipped core glass crucible 27, a nozzle-equipped cladding crucible 28 with a nozzle arranged on the outside concentrically with the nozzle of the crucible 27, a core glass 29, a cladding glass 30, A coating material container 31 with a nozzle, which is concentric with the nozzle of the cladding crucible 28 and has a nozzle further outside, does not decompose at the drawing temperature of the glasses 29 and 30 and the glass 2
A thermoplastic coating 32 having a viscosity equal to or lower than 9°30, a second glass 29.30 poured into the drawing crucible 27.28 to maintain it at the drawing temperature.
A heater 33 is a heating means for heating the coating material 32, a heater 34 is a second heating means for adjusting the viscosity of the coating material 32 to an appropriate value, a gas introduction pipe 35 for extruding the coating material 32 by gas pressure, a gas It is comprised of a gas pressure regulator 36 that adjusts the gas pressure within the introduction pipe 35 and a gas introduction port 37 for high-pressure gas. Although the details will be described later, by selecting the material of the coating material 32, the heater 33 for the crucible 27, 28 can be omitted, and at least the heater for the coating material 32 can be used as the second heating means. 34 is fine.

FIG. 3 is a detailed view of the nozzle part in the wire drawing section B of the present invention, in which a core glass crucible 27 and a clad glass crucible 28 constitute a double crucible, and a covering material crucible is formed on the outer periphery of the double crucible. The nozzles provided at the tip of each crucible are concentrically formed for core glass, clad glass, and coating material in order from the inside. In addition, the tip of the nozzle has a core glass 29. In order to prevent the clad glass 30 and coating material 32 from flowing out from each crucible before wire drawing, the bottom plug 38 is equipped with a multi-stage protrusion that matches the shape of the tip of the nozzle, and for attaching and removing the bottom plug 38. A rod 39 is provided.

As described above, in the fluoride glass fiber manufacturing apparatus according to the present invention, the glass melting section A and the drawing section B are separated in airtight containers, and the core glass 29. The structure is such that the clad glass 30 and the covering material 32 can be drawn simultaneously without being exposed to the atmosphere.

Next, as the core glass 13, 53ZrF420BaFz
2ONaF 4 LaFi 3 AlF3. 39.7 ZrFa 13.3 as clad glass 14
HfFa 18BaFz 22NaF 4 La
F3-3 AIF, A method of manufacturing a fiber using the apparatus of the present invention shown in FIG. 2 using fluororubber as the coating material 32 will be described.

(1) First step ■ Inert gas such as argon, nitrogen or helium or fluorine gas is introduced from the gas inlet 19, and the container 1
6, the chamber formed by the jig 15 and the lid 17 of the container 16 is made to have an inert gas or fluorine gas atmosphere, and the inside of the drawing section B of the container 16 is made to be an inert gas atmosphere.

(2) The core and clad raw material glasses loaded in the glass melting crucible 12 are heated in an electric furnace 22 at about 800° C. for about 1 hour to melt them.

(2) Next, the molten glass 13.14 is heated to approximately 500°C.

■ Inject Ar gas from the inert gas inlet 21,
Core glass 13 and cladding glass 14, which are in a molten state under the pressure of r gas, are injected from glass melting section A into crucibles 27 and 28 of wire drawing section B via pipe 25.

(2) Second step ■ The molten core glass 29 and clad glass 30 poured into the nozzle-equipped core glass crucible 27 and the nozzle-equipped clad glass crucible 28 are heated by the heater 33 to a drawing temperature of 325°C. do.

On the other hand, the fluororubber 32, which is the coating material loaded in the coating material container 31, is heated by the heater 34, which is the second heating means.
It is melted at about 280°C.

(3) Third step ■ Ar gas is injected from the high pressure gas inlet 37, and the Ar gas pressure is adjusted to 1 kg/crA using the gas pressure regulator 36.

■ Pull out the bottom plug 38 with the rod 39, and remove the core glass 29°, clad glass 30, and covering material 32 by 15 m from each nozzle.
The fiber 40 having a three-layer structure is formed at once by drawing out the fiber at a speed of 1/2 min, and the fiber 40 is wound up by the winding drum 11.

Through the above steps, a core with a diameter of 15μI and a diameter of 150μ
It was possible to continuously manufacture approximately 700 m of fluoride glass fiber consisting of a three-layer structure of a cladding layer of 5 μm thick and a coating layer of 5 μm thick. Further, the manufactured fiber 40 was not damaged even during operations such as winding on the drum 110, and microscopic observation did not show any factors that degrade the fiber strength such as crystal phase precipitation or scratches on the fiber surface.

In addition, in the above explanation, the case where fluororubber is used as the coating material 32 was explained as an example, but in addition to this, it does not change physicochemically at the drawing temperature of fluoride glass (320-330 degrees), and There are many resins whose viscosity is comparable to or lower than that of fluoride glass, such as fluororesins and polycarbonate resins, and there are no problems in carrying out the present invention. In particular, among fluororesins, the melt viscosity of a polymer of ethylene and tetrafluoroethylene (ETFE) is 10'-10' voids at 300-330 degrees.
A manufacturing apparatus and a manufacturing method in which such a resin, which exhibits viscosity properties comparable to those of fluoride glass, is used for the covering material 32 will be described.

FIG. 4 is a schematic diagram of another drawing part B according to the present invention,
The difference from FIG. 2 is that the heater 33, which is the second heating means for adjusting the core glass 29 and Talarad glass 30 to the drawing temperature, is omitted.

By omitting the heater 33, the clad glass crucible 28 can also serve as the inner wall of the coating material container 31, so a triple crucible structure in which the crucibles 27 and 28 of the wire drawing section B and the container 31 are integrated is also possible. The device can be simplified.

Further, the manufacturing method is also simplified because (1) and (2) in the second step described above can be adjusted at once using only the heater 34.

In addition, in order to make the explanation easy to understand in the above-mentioned manufacturing method, the material of the fluoride glass was specified and described, but it can also be applied to the manufacturing of other fluoride glasses.

(Effects of the Invention) As explained above, in the method and apparatus for manufacturing a fluoride glass fiber with a coating layer of the present invention, the entire fiber manufacturing process is carried out in a controlled atmosphere, which prevents contamination of impurities, oxygen and moisture. Since there is no precipitation of crystalline phase due to reaction or generation of scratches during the fiber manufacturing process, there are few factors that deteriorate the strength of the fiber.Furthermore, it is easy to mechanize and automate the manufacturing process without relying on human labor. Good yield and industrial productivity.

Therefore, it is possible to manufacture a long, high-strength, low-cost fluoride glass fiber with a coating layer that has little transmission loss and is used in optical communications, etc., and the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of a manufacturing apparatus for manufacturing fluoride glass fiber using the conventional double crucible method, FIG. 2 is a schematic system diagram of a manufacturing apparatus for manufacturing fluoride glass fiber according to the present invention, and FIG. FIG. 4 is an enlarged block diagram of the nozzle portion of the manufacturing apparatus according to the present invention, and FIG. 4 is a schematic diagram showing another structural example of the drawing section B in the manufacturing apparatus according to the present invention. l...Core glass, 2...Tararad glass, 3...
- Crucible for core glass, 4... Crucible for clad glass, 5... Electric furnace for heating crucible for glass melting, 6...
・Fiber wire diameter monitor, 7... Coating container for coating resin coating, 8... Coating material (coating resin),
9... Furnace for curing coating resin, 10... Capstan for fiber drawing, 11... Fiber winding drum, 12
... Crucible for melting fluoride glass, 13... Core glass in molten state, 14... Talarado glass in molten state, 15... Jig for holding crucible for melting fluoride glass, 16 ... Container for maintaining an inert atmosphere, 17... Container lid, 18... Puff King,
19...Inlet for inert gas or fluorine gas,
20... Gas outlet, 21... Inert gas inlet for extruding molten glass, 22... Gas outlet, 23... Inert gas inlet, 24...・Electric furnace for glass melting, 25... Pipe for glass injection, 26...
・Backing, 27... Crucible for core glass with nozzle, 28... Crucible for clad glass with nozzle, 2
9... Core glass, 30... Thalassode glass, 31
... A container for coating material equipped with a nozzle arranged concentrically with the nozzle of the crucible for cladding, 32... Covering material,
33... Heater for heating crucible for wire drawing, 34... Heater for heating coating material, 35... Gas introduction pipe, 36...
...Gas pressure regulator, 37...High pressure gas inlet, 38.
...Bottom plug, 39...rod for attaching and removing the bottom plug, 40.
··fiber.

Claims (2)

[Claims] (1) A nozzle arranged in a wire drawing section maintained in an inert gas atmosphere after melting a core glass made of fluoride glass and a clad glass in an inert gas or fluorine gas atmosphere in a glass melting section. A first step of injecting the core glass and the clad glass in a molten state into a double crucible with a nozzle formed concentrically, adjusting the temperature of the core glass and the clad glass to the drawing temperature, and The temperature of the thermoplastic coating material, which does not decompose at the drawing temperature, is set to a temperature equal to or lower than the viscosity of the core glass and cladding glass in a container with a coating material supply nozzle formed concentrically around the outer periphery of the double crucible. a second step of adjusting the coating so that the coating material adheres to the surface of the outer clad glass of the core glass and clad glass flowing out from a nozzle provided at the tip of the double crucible; a third step of simultaneously forming a three-layer structure of the core glass, the cladding glass, and the coating material by extruding the material. (2) The glass melting section includes a first heating means that heats and melts a core glass made of fluoride glass and a cladding glass above their melting points, and a first heating means that heats and melts a core glass made of fluoride glass and a cladding glass, and at the time of melting, the core glass and cladding glass are heated with an inert gas or a fluorine-based gas. The drawing section for drawing the molten core glass and clad glass supplied from the glass melting section into a fiber has two nozzles formed concentrically, and has a first gas introducing means to create an atmosphere of A double crucible with a nozzle that accommodates the core glass and clad glass melted in a glass melting part in an inert gas atmosphere, and a nozzle is formed concentrically with the two nozzles on the outer periphery of the double crucible. at least one second heating means for adjusting the core glass and clad glass in the double crucible and the coating material in the container to a desired temperature; and a second gas introduction means for introducing gas,
A three-layer structure of the core glass, the clad glass, and the coating material drawn out from the drawing section is formed simultaneously, and the fluoride glass fiber with a coating layer is further provided with a winding section for drawing out and winding the fluoride glass fiber with a coating layer. Glass fiber manufacturing equipment.