KR100564886B1 - A Method for Producing a Preform for Plastic Optical Fiber Having a Graded index profile - Google Patents

Abstract

The present invention discloses a method for producing a polymer optical fiber base material having a hill-shaped refractive index distribution to enable large-capacity data transmission by repeatedly stacking and copolymerizing polymer discs having different refractive indices and monomers.

The present invention is to increase the optical signal bandwidth and increase the transmission bandwidth as the refractive index of the optical fiber has a change in the axial direction. To this end, the present invention proposes a method of manufacturing a polymer optical fiber base material having a hill-shaped refractive index distribution to produce a polymer optical fiber base material copolymerized by repeatedly stacking polymer discs and monomers having different refractive indices.

In this manner, the present invention has a refractive index distribution that changes periodically along the longitudinal direction of the optical fiber, thereby manufacturing an optical fiber having an increased bandwidth and a significantly improved transmission speed by mode mixing, including image information. There is a useful effect that can transmit high-quality multimedia information more quickly.

Description

A method for producing a preform for plastic optical fiber having a graded index profile

1 is a schematic diagram of an apparatus for manufacturing a polymer optical fiber base material according to the present invention.
2 is a cross-sectional view and a side surface of the high refractive polymer disc 80 presented in the present invention.

<Description of the symbols for the main parts of the drawings>

10: monomer reservoir 20: monomer solution 30: flow rate control device

40: cladding 50: low refractive polymer 60 high refractive polymer

70: heater 80: polymer disc
81: high refractive polymer disc side view

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BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to the manufacture of a plastic indexed fiber optical fiber (GI-POF) preform having a refractive index distribution that changes gradually along the axial direction. The present invention relates to a method of manufacturing a GI-POF base material having a refractive index distribution that periodically changes along the longitudinal direction of an optical fiber by laminating and copolymerizing two polymer layers having different refractive indices and a single molecule.

In the case of silica optical fibers, multi-mode optical fibers used in optical networks have a core diameter of about 10 microns or more and are much larger than single-mode optical fibers, so that they are light sources, detectors or optical fibers. While the connection between the two is easier than the single-mode fiber, there is a disadvantage in that a large amount of data cannot be transmitted due to the modal dispersion phenomenon caused by the difference in propagation speed between the modes.

In order to solve this multimode dispersion problem, a GI grade (graded index) silica optical fiber having a gradually changing refractive index distribution has been developed by forming the refractive index of the core portion of the optical fiber in a smooth curve. This GI type plastic optical fiber is easier to handle than silica fiber and has a wider transmission bandwidth. Therefore, research and development for the short distance optical communication and home network is progressing. Meanwhile, a silica glass photonic crystal fiber or a porous fiber has been developed in which a hollow cylinder-shaped glass tube is bundled into a bundle, and a hollow cylindrical glass rod is inserted at the center thereof. It has a large diameter but operates in a single mode or in a multimode mode in which the number of induced modes is greatly reduced, which makes it easy to use and at the same time increases the data transmission rate. Have However, such a photonic crystal optical fiber has a disadvantage that it is not suitable as an optical signal transmission optical fiber because the process of manufacturing the base material and the fiber drawing conditions are difficult. GI-POF manufacturing process has a surface gel effect, but there is a high refractive index additive, a method using a specific molecular weight difference of the single molecule, and a manufacturing method by rotation, but the manufacturing process is very difficult and difficult to achieve the desired refractive index distribution.

Therefore, in order to solve this problem, the present inventors repeatedly laminated convex lens-type high-refractive-index polymer plates and monomolecules in manufacturing a plastic optical fiber base material. It has begun to develop a method for manufacturing an optical fiber base material.

Accordingly, an object of the present invention is to have a hill-shaped refractive index distribution that can increase the optical signal bandwidth and increase the transmission bandwidth as the refractive index of the optical fiber having a gradient-index has an axial change It is to provide a method for producing a polymer optical fiber (GI-POF) base material.

In order to achieve the above object, the present invention provides a method for producing a polymer optical fiber base material having a hill-shaped refractive index distribution that changes periodically along the longitudinal direction of the optical fiber by periodically dropping and copolymerizing the polymer disc and the monomer mixture.

Hereinafter, the present invention will be described in detail.

In the present invention, in order to form a periodic refractive index distribution in the longitudinal direction in the optical fiber base material, the base material is manufactured using the interfacial gel phenomenon at the interface between the polymer disc and the single molecule by stacking polymer discs and single molecules having different refractive indices. An additive for controlling the refractive index of the polymer disc may be mixed therein, and the base material may be prepared by laminating polymerization while dropping them alternately. Since the drop polymerization method can reduce air bubble formation or residual monomers due to the volume reduction occurring during the bulk polymerization of the polymer, it is possible to reduce bubble generation and scattering due to residual monomers at the time of fiber extraction.

Monomers used in the present invention include methyl methacrylate (MMA), polystyrene (PS) and the like. An additive for controlling the refractive index of the monomer, for example, polystyrene (PS), polycarbonate (PC), bromobenzene, etc. may be mixed as a refractive index increasing agent, or used as a refractive index reducing agent. Fluorine resin can be added and used. These additives are preferably used in an amount of 5 to 10% by weight based on the weight of the monomers.

In addition, when the monomer or monomer mixture is added dropwise onto the polymer layer, the dropping amount is supplied to the reactor with a period of 5 to 10 seconds in an amount of 2 to 4 cc, preferably about 3 cc, once.

In the copolymerization process, an initiator and a chain transfer agent may be additionally added to the monomer or the monomer mixture, and the amount thereof is not particularly limited and depends on the physical properties of the desired polymer and the manufacturing process conditions.

In the apparatus for manufacturing the base material according to the present invention as shown in FIG. 1, a polymer disc 80 consisting of convex lenses is provided, and monomers 20 having different refractive indices are stored in the monomer reservoir 10. A flow rate control valve 30 for periodically supplying the stored monomers 20 is attached, and the monomers 20 having different refractive indices are periodically inserted into the cladding while the flow rate control valve 30 is intermittently opened and closed ( 40). These polymer discs 80 and monomers 20 are alternately supplied dropwise to each other to copolymerize to form polymer layers 50 and 60 alternately from the bottom in the interior of the cladding 40. An optical fiber base material having a hill-shaped refractive index distribution having

Thus prepared optical fiber base material can be heat-treated at 100 to 110 ℃ under vacuum, this heat treatment process to complete the polymerization of the monomer 20, and to reduce the loss due to scattering in the optical fiber by evaporating the unreacted monomer and water. You can.

The reactor material used in the method of the present invention is not particularly limited, but any material may be used as long as the material has good thermal conductivity and does not react with the raw material monomer or the produced polymer.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Example 1 Preparation of Optical Fiber Base Material

Using a reactor (50 mm in diameter), polymethyl methacrylate (PMMA) and fluororesin were mixed and polymerized to prepare a tube-type cladding (thickness 10 mm) having a diameter of 30 mm in the inner void space. This cladding tube is made of polymethyl methacrylate (PMMA), and mixed with methyl methacrylate (MMA) solution and bromobenzene at 8: 2 to prepare a 200 micrometer thick polymer disc, and the disc The diameter of is 25 mm. After inserting it into the reactor, a monomer mixed solution containing methyl methacrylate (MMA) solution and bromobenzene in a ratio of 9: 1 was periodically supplied to the inside of the cladding in a quantity of 3 cc each. At this time, the temperature in the reactor was maintained at 90 ℃. The PMMA and the monomer mixture solution, in which the high refractive index polymer disk and the low refractive index monomolecule were periodically supplied to the reactor, were copolymerized, respectively, to prepare a polymerized optical fiber base material in which thin films were alternately laminated. Placed in an oven and heat treated at 100 ℃.

Example 1 Preparation of Optical Fiber

The optical fiber base material prepared in Example 1 was stretched at an electric furnace temperature of 270 ° C. in a heating furnace for optical fiber extraction at a speed of 10 m / min to obtain an optical fiber having a diameter of 700 μm.

As described above, the base material prepared by periodically dropping and copolymerizing a polymer disc and a monomer solution having different refractive indices according to the present invention has a hill-shaped refractive index gradient in the axial direction and increases the bandwidth of the optical signal. It can manufacture optical fiber that can increase more than 100 times than PMMA series polymer optical scintillation transmission speed with stepped refractive index, and it enables fast information transmission and high-definition multimedia transmission through the Internet. The information can be quickly transmitted through a network in the hospital, which has a useful effect that can be used for diagnosis and treatment of patients.

Claims (5)

A method for producing a polymeric optical fiber base material having a hill-shaped refractive index distribution, characterized in that the polymer disc and monomer solution having different refractive indices are repeatedly added and copolymerized. The method of claim 1, A method for producing a polymeric optical fiber base material having a hill-shaped refractive index distribution, characterized in that the monomer solution contains a refractive index increasing agent. The method of claim 1, The center of the polymer disc is convex, characterized in that the manufacturing method of the polymeric optical fiber base material having a hill-shaped refractive index distribution. The method of claim 2, A refractive index increasing agent is polystyrene, polycarbonate, bromobenzene, and a refractive index reducing agent is a manufacturing method of a polymeric optical fiber base material having a hill-shaped refractive index distribution, characterized in that the fluorine resin. The method of claim 1, Method for producing a polymeric optical fiber base material having a hill-shaped refractive index distribution, characterized in that the monomer solution contains a refractive index reducing agent.

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