JPS6048722B2 - Method for manufacturing polycrystalline core-clad ion crystal optical fiber - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing a polycrystalline core-clad ion crystal optical fiber, in which a rod-shaped polycrystalline preform consisting of a square core and a cladding is formed by extrusion, and then A polycrystalline core-clad type ionic crystal optical fiber is stably manufactured at low cost by rolling with heated rolls while extruding.

Ionic crystal optical fibers, which are made of ionic crystals such as alkali metal halides, alkaline earth metal halides, silver halides, and thallium halides, have low transmitted light loss and are expected to have great potential in optical fiber communications. has been done.

Now, there are two types of these ion crystal optical fibers: polycrystalline fibers and single crystalline fibers. Single crystal ion crystal optical fibers have low loss but are difficult to manufacture. Although a polycrystalline ion crystal optical fiber has a larger loss than a single-crystal one due to reflection on each crystal surface, it is easy to manufacture, and in a long wavelength range, loss due to reflection on a crystal surface is relatively small. Therefore, even polycrystalline ion crystal optical fibers can be used for short-distance optical fiber communications. In view of the above circumstances, it is an object of the present invention to produce polycrystalline core-clad type ion crystal optical fibers stably and in large quantities at low cost.

This invention will be explained in detail below.

Although there are various apparatuses for manufacturing the polycrystalline core-clad type ion crystal optical fiber of the present invention, representative ones are shown in FIGS. 1 and 2 and will be explained based on these.

What is shown in FIG. 1 is an apparatus for manufacturing an ionic crystal preform having a core-clad type structure.

The inner barrel 1 is filled with ionic crystals 3 as a core part, and the outer barrel 2 coaxially with the inner barrel 1 is filled with ionic crystals 4 as a cladding part. The ionic crystal used here is LiF)NaF)NaClNKCI)KB
r) KI) Alkali metal halides such as CsBr, Csl, CaF. , BaF. , MgF. Alkaline earth metal halides such as 1CUC12, AgC1
, halides of copper group elements such as AgBr, ncl, T
1Br) and other halides of thallium,
A combination is selected from the above group of ionic crystals such that the refractive index of the ionic crystal 3 in the core portion is larger than the refractive index of the ionic crystal 4 in the cladding portion. Next, the inner ram 6 and the outer ram 7 are extruded while being heated by the heater 5. Then, the ionic crystals 3 and 4 are plasticized by heat from the heater 5 and internal heat generation due to compression. Plasticized ionic crystal 3
, 4 are further pressed, and a polycrystalline preform 9 of ionic crystal having a rod-shaped core-clad structure is obtained in the cylinder 8. In this process, the temperature of the ionic crystals inside the inner barrel 1, outer barrel 2, and cylinder 8 is slightly lower than the melting point of the ionic crystals in the core and cladding parts near the exit of each barrel, as shown in Figure 1. must be adjusted accordingly. If the temperature is higher than the melting point of either of the ion crystals, both will mix and become uniform, making it impossible to obtain the desired core-clad type polycrystalline ion crystal optical fiber. Next, the shilling 8 filled with the polycrystalline preform 9 is set in the apparatus shown in FIG. This device rolls a rod-shaped polycrystalline preform 9 into an optical fiber 24. The rod-shaped polycrystalline preform 9 is heated to below its melting point by a heater 21 and pressed by a ram 22. . The pressed polycrystalline preform 9 is passed through a pair of heated rolling rolls 23 provided at the outlet of the cylinder 8 and rolled. By repeating this rolling operation several times while gradually decreasing the diameter of the hole of the rolling roll 23, a diameter of several hundred PTrL is obtained.
, polycrystalline core-clad ion crystal optical fiber 2
4 is obtained. During this rolling process, the crystal grains of the polycrystalline preform, which had been separated one by one, became tightly intertwined.
A polycrystalline ion crystal optical fiber 24 with high mechanical strength is obtained. The obtained polycrystalline core-clad ion crystal optical fiber 24 is continuously wound by a winder (not shown). According to the method for manufacturing a polycrystalline core-clad type ionic crystal optical fiber of the present invention, a rod-shaped polycrystalline preform having a core-clad structure is first formed by an extrusion method, and then this is extruded and rolled. As a result, a long polycrystalline core-clad ion crystal optical fiber can be produced stably at low cost, and the ion crystal is not melted. It has the advantage that no segregation phenomenon occurs and the optical fiber is less likely to be contaminated.

This invention will be specifically explained below with reference to Examples.
[Example] As the ionic crystal of the core part, TlBr42wt% and Tl
An ionic crystal mixture (hereinafter referred to as KRS) consisting of I58Wt%
It says -5.

) as the ionic crystal of the cladding part, TlCl6Owt
% and NBr4Owt% (hereinafter referred to as KRS-6) are prepared. Inner barrel 1 of the device shown in Fig. 1 has an inner diameter of 15 mm and a length of 15 mm.
-5 filled with 90 da, outer barrel 2 inner diameter 21wr! nφ
, outer diameter 487mφ, length 15077Z77E KRS-
6 was filled to 670 Da. Next, a breaker plate is set at the outlet of the barrels 1, 2), and the rams 6, 7 are pushed out to make the barrel internal length 67-. Inner diameter 10.5wrmφ,
Set the cylinder 8 with a length of 4207rgn, and turn on the heater 5.
Barrels 1 and 2 were heated to 250°C, and the barrel outlet was heated to 300°C.
Heat to °C, press rams 6 and 7, and press cylinder 8.
A polycrystalline preform 9 with a core-clad structure is extruded therein. Polycrystalline preforms with a core-clad structure for three cylinders were obtained by filling the ionic crystal once. Next, this cylinder 8 is set in the apparatus shown in FIG.

The rolling roll 23 is heated to 300°C, and the cylinder 8 is heated to 250°C.
It is heated to ℃. The polycrystalline preform is extruded by ram 22 and passed through rolling rolls 23 . The circumferential speed of the rolling roll 23 is 17 TL/Min. The hole shape of the first rolling roll is 6.3-φ, and the following is 3.8Twtφ
, 2.37wtφ, 1.4TWLφ, 0.83-φ, 0
．． The rolling operation is repeated by reducing the hole diameter to 5Tfrmφ and 0.3m771φ. Finally, a polycrystalline core-clad ion crystal optical fiber (5007T1) having an outer diameter of 300 μm and a core diameter of 100 μm was obtained. The refractive index of the core portion of the obtained polycrystalline core-clad ion crystal optical fiber was 2.4 at λ=4μ, and the refractive index of the cladding portion was 2.18 at λ=4μ.

[Brief explanation of the drawing]

Figures 1 and 2 show an example of manufacturing equipment used in the method of the present invention. Figure 1 is an explanatory diagram showing the equipment and temperature distribution for forming a polycrystalline preform, and Figure 2 is an explanatory diagram showing the equipment for forming a polycrystalline preform and temperature distribution. FIG. 2 is an explanatory diagram of an apparatus for manufacturing a polycrystalline ion crystal optical fiber from a preform. 3...Ionic crystal in the core part, 4...
Ionic crystal of cladding part, 9... Polycrystalline preform, 23... Rolling roll, 24...
...Polycrystalline core-clad ion crystal optical fiber.

Claims (1)

[Claims] 1. A method of manufacturing a polycrystalline core-clad type ionic crystal optical fiber by forming an ionic polycrystalline preform consisting of a core and a cladding by an extrusion method, and then extruding and rolling this polycrystalline preform.