JPS61162008A - Production of plastic optical fiber - Google Patents

Abstract

PURPOSE:To form a refractive index distribution characteristic having the prescribed refractive index in the radial direction with respect to the axis of an optical fiber by immersing an optical fiber resin into anhydrous hydrofluoric acid and using an electrolytic fluorination reaction. CONSTITUTION:The decrease in the refractive index of the optical resin such as polymethyl methacrylate (PMMA) when added with fluorine is noticed in this method and the core surface is fluorinated or fluorine is implanted to the core surface by the electrolytic fluorination reaction of anhydrous hydrofluoric acid. The core having the refractive index distribution characteristic in which the refractive index on the front side is lowest, i.e., n3=1.39 with respect to n1=1.49 the refractive index intrinsic to the core is formed by fluorinating the core surface. Namely, the optical fiber of which the refractive index decreases gradually with the increase in the distance from the optical axis in the radial direction with the optical axis 1 as vertex is easily realized.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a plastic fiber for optical waveguide.

In particular, the present invention relates to a method of manufacturing a graded inte x type plastic optical fiber.

Plastic optical fibers are widely used as short-distance optical transmission lines between electronic devices that transmit and receive optical signals, where transmission loss is not as much of an issue, but compared to glass fibers for optical communications.

Regarding light transmission properties, although it absorbs light in the infrared wavelength range, it is easy to manufacture and therefore inexpensive, and has features such as high flexibility and mechanical strength.

Conventionally, optical waveguide fibers are made of optical resin, such as polymethyl methacrylate resin (P), as the core.

lyMethyl MethAcrylate PM
MA) + polycarbonate resin (PC), or a copolymer resin of PMMA and PC, etc. are used. Furthermore, since adding fluorine to the resin lowers the optical refractive index, a light-focusing fiber in which fluorine is molded as a core-exterior resin layer has been put into practical use. That is, a step index type fiber in which the refractive index of the core and the outer protective resin attached to the core changes stepwise has been put into practical use.

On the other hand, so-called graded-index core fibers, which have light focusing properties in which the refractive index of the core gradually decreases from the axis toward the periphery, have various problems from a manufacturing standpoint, and their practical application has been delayed. .

The present invention was proposed based on the need for practical use of an optical fiber in which the refractive index continuously decreases from the core axis toward the radial periphery.

[Prior art and problems to be solved by the invention] FIG. 2 shows the refractive index characteristics of a step-index fiber, and in the figure, 1 is the optical axis of the core.

Core diameter (d1 part 3 is n1 where the medium refractive index n is homogeneous)
=1.49, and its outer periphery is a cladding layer 4 on the outer periphery of the core, which is a resin cladding with a homogeneous and uniform refractive index nz (nz < fi, ) blended with fluorine. The layer 4 can also be formed of a curable silicone resin that is irradiated with ultraviolet rays.

By the way, for the step index type in which the incident light is totally reflected at the interface between nl and nl, the refractive index in Figure 3 has the core optical axis 1 as the apex and the refractive index n1 gradually decreases toward the periphery to n3. Distributed characteristic fibers are complicated to process and have problems from a cost standpoint.

[Means for solving problems] The above problem is.

The present invention has been solved as a plastic optical fiber in which the optical fiber resin is immersed in anhydrous fluoric acid and an electrolytic fluorination reaction is used to form a predetermined refractive index distribution characteristic in the radial refractive index with respect to the optical fiber axis. Ru.

[For production]

Fluorinated polyethyl methacrylate (PMMA)
The focus is on the reduction of the refractive index of the above optical resins, and this is achieved by fluorination treatment on the core surface by electrolytic fluorination reaction of anhydrous hydrofluoric acid, or by fluorine injection treatment. Yes (fluorination method.

It is also called the Simons process method. Reference, Chemical Review No. 2717-36, 1980").

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the example of the fluorination reaction of optical resin shown in FIG.

FIG. 1 is a schematic diagram of an electrolytic cell in which a fluorination reaction of plastic fibers is carried out. The optical fiber 10 is.

Generally, it is formed into a fiber shape by discharging it from an optical resin melting tank through a nozzle.

The fluorination reaction electrolytic cell 11 is formed of a container made of iron or monel. Although the anhydrous fluorinated acid solvent 12 in the tank is said to have a high ionization ability, it dissolves organic compounds such as the above-mentioned PMMA resin by accepting protons and becomes conductive.

In the electrolytic cell 11, a positive electrode 13 made of nickel or a nickel alloy (monel, etc.), a cathode 14 made of iron, &r4, etc. are used as electrode substrates, and fluorination treatment is carried out at an appropriate electrolytic voltage.

For example, the above-mentioned PMM^ cyclic compound can be produced by the above-mentioned fluorination treatment.

Through the process of extracting hydrogen from methane CH, CH becomes a perfluorocarbon compound, CF3.
will be replaced with

By performing fluorination treatment on the core surface including such a process, the refractive index on the surface side is the lowest, n3 = 1.39, compared to the core's inherent refractive index, n1 = 1.49. A core with a refractive index distribution characteristic is formed. In other words, an optical fiber whose refractive index gradually decreases with the optical axis 1 as the apex as it moves away from the optical axis in the radial direction can be easily realized.

〔Effect of the invention〕

As explained above, in the present invention, the method of manufacturing a conventional optical fiber core resin with a graded refractive index by simply immersing it in an electrolytic fluorination reaction tank and electrolyzing it has great practical value.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electrolytic cell as an example of a method for fluorinating plastic fibers. FIG. 2 is a refractive index distribution characteristic diagram of a step index type optical fiber. 4 is a refractive index distribution characteristic diagram of the graded index type fiber core according to the present invention shown in FIG. 3. FIG. In the figure, 11 is a fluorination reaction electrolytic cell.

Claims (1)

[Claims] The optical fiber resin is immersed in anhydrous hydrofluoric acid and an electrolytic fluorination reaction is used, and the radial refractive index of the optical fiber resin is formed as a predetermined refractive index distribution characteristic with respect to the fiber axis. Method of manufacturing plastic optical fiber.