KR20040087643A - Method of Fabricating a Preform for Plastic Optical Fiber - Google Patents

Abstract

PURPOSE: A method for fabricating a preform of a plastic optical fiber is provided to diffuse easily a monomer of a high refractive index by using supercritical fluid or high-pressure fluid as a diffusion medium. CONSTITUTION: A cylinder(1) is used for supplying a reacting medium. A control unit(4) is used for monitoring a pressure controller(2) and a temperature controller(3). An input unit(5) mixes a monomer with the reacting medium and inputs a mixture of the monomer and the reacting medium. A cylindrical rotating reactor(6) is used for polymerizing the mixture and forming a polymer. A driving shaft(7) is used for rotating the cylindrical rotating reactor. A heating source and a light source(8) are used for performing a monomer polymerization process.

Description

Method for manufacturing base material for plastic optical fiber {Method of Fabricating a Preform for Plastic Optical Fiber}

The present invention relates to a method for producing a base material for plastic optical fibers, and more particularly, to prepare a base material for plastic optical fibers more efficiently by using a supercritical or high pressure fluid as a diffusion medium to facilitate the diffusion of the monomer into the polymer. Provide a way to do it.

Communication optical fibers are classified into single-mode fiber and multi-mode fiber according to the transmission mode of the optical signal. Most of the optical fiber for long distance high speed communication currently used is a step-index single-mode optical fiber based on quartz glass, and the glass optical fiber has a fine thickness of only 5 to 10 탆 in diameter. Therefore, such glass optical fibers are very difficult to align and connect, resulting in high cost loss. On the other hand, multimode glass fiber having a larger diameter than single mode fiber can be used for short-distance communication such as LAN (local area network), but it is difficult to be widely used due to the high cost and fragile disadvantage of connection. Many. Thus, metal cables, such as twisted pairs or coaxial cables, have been used primarily for short-range communications within 200m, such as LANs. However, since the metal wire has a maximum information transfer rate (or bandwidth) of about 150 Mbps, it cannot meet the future transfer rate standard because it cannot reach 625 Mbps, which is the Asynchronous Transfer Mode (ATM) standard of the 2000s. There was no. For this reason, there have been many efforts and investments in the development of polymer optical fibers that can be used for short-range communication such as LAN over the last decade in Japan and the United States. Plastic optical fiber (hereinafter referred to as 'POF') is a polymer material manufactured by extrusion molding because it is easy to align or connect because its diameter can reach about 0.5 to 1.0 mm, which is 100 times larger than glass fiber due to its flexibility. The use of connectors allows for significant cost savings.

On the other hand, POF is a step-index structure in which the refractive index change in the radial direction is stepped (hereinafter, referred to as 'SI'), or a graded index (hereinafter, referred to as 'GI') in which the refractive index gradually changes in the radial direction. Although the SI POF has a large modal dispersion, the signal transmission speed (or transmission bandwidth) cannot be faster than the metal cable, whereas the GI POF has a modal dispersion. Because it is small, it can have a high bandwidth. Therefore, GI POF is known to be suitable as a medium for short distance high speed communication due to the cost saving effect resulting from the thick diameter and the high information transmission speed due to small modal dispersion.

As a conventional method of manufacturing GI POF, the method of interfacial gel polymerization by Professor Koei Kei of Japan Keio University was first published in 1988 (Koike, Y. et al., Applied Optics, vol. 27, 486). 1988), and then many processes using dopants have been published, but most of these processes can be roughly divided into two types of processes.

First, a batch process of preparing a GI POF by heating and stretching the base material after forming a preform, that is, a preform having a refractive index that changes in the radial direction using a polymer and a relatively small molecular weight and a high refractive index, that is, a dopant. There is a batch process.

Second, after the polymer fiber is produced by the extrusion process, a low molecular weight dopant added to the fiber is extracted in the radial direction, or conversely, a low molecular weight material is added in the radial direction to prepare GI POF. have.

The first process was developed by Professor Koike and succeeded in producing GI POFs with a transfer rate of 2.5 Gbps, and the second process is known to succeed in manufacturing POFs with relatively high transmission bandwidths. Most of the above-described methods use well-known facts that the process proceeds while rotating in a state of laying down or standing so that the refractive index gradient does not collapse by gravity.

The method, developed by Van Duijnhoven and Bastiaansen of the Netherlands and disclosed in WO 97/29903 and registered in US Pat. No. 6,166,107, uses a very powerful rotation of about 20,000 rpm using rotation. This method differs from other prior arts by polymerizing a mixture of different high density and low refractive index monomers and low density and high refractive index monomers or a mixture of polymers having low refractive index under very strong centrifugal force. According to the density gradient, a gradient of concentration and thus a refractive index gradient are used. However, in the above method, since the monomer having a higher density must have a smaller refractive index than the monomer having a lower density, the selection of the monomer to be used is limited. In addition, the present invention does not mention any problem of volume shrinkage that always occurs in the polymer reaction. That is, when the monomer is polymerized to become a polymer, volume shrinkage occurs, and the hollow fiber-like hollow material is formed at the center of the base material for plastic optical fiber produced by centrifugal force. It is difficult to say that there is an improvement in manufacturing time compared to other methods of manufacturing the base material using other rotations because additional monomer injection process is required to fill this hollow. In addition, when the base material is made while filling the hollow of the base material in which the volume shrinkage occurs, and the fiber is manufactured using the base material, discontinuous surfaces appear in the refractive index distribution, which causes a rapid decrease in the amount of light and the amount of light.

On the other hand, the inventors have devised and applied a method for manufacturing a base material using a hollow-proof reactor as a method of manufacturing a base material for GI plastic optical fiber that can solve the problems of the volume shrinkage as described above. (Korean Patent Application No. 2001-78965 And US patent application Ser. No. 10 / 197,215). In this method, an input unit having a reactant inlet for introducing a reactant into the entire reactor and the input unit and a barrier wall are positioned between the reactor and the reactor and a reactor having a flow path communicating with the input unit in the center of the barrier wall. Installed between the flow path of the reaction portion and the reactant inlet of the input portion so that the hollows generated from the reactant inlet space of the input portion do not continue to the reaction portion, and having one or more flow paths allowing the reactant of the input portion to flow into the reaction portion, It is a method of manufacturing a base material for plastic optical fibers by polymerizing under rotation by appropriately adding a monomer mixture having different refractive indices using a hollow prevention reactor including one or more hollow blocking structures.

In addition, there is a method developed by Triphathy et al in the United States as a method of manufacturing a base material that the refractive index changes in the radial direction (US Patent No. 5,935,491). This method creates a cylindrical base material containing a polymer material and additives with different refractive indices, and immerses it in a medium that is non-solvent for the polymer material and compatible with the additive. In order to prepare a base material having a refractive index change in the radial direction, a supercritical fluid (SCF) was used as the reaction medium, thereby shortening the manufacturing time. However, this method can not use a solvent as a reaction medium in the polymer material, even if a non-solvent is used to swell the base material to change the shape of the base material after the base material manufacturing, the outer edge of the base material (edge) Since the refractive index is steeply lowered (see FIG. 3B of U.S. Patent No. 5,935,491), there is a disadvantage in that an optical fiber has to undergo an additional process of manufacturing a clad after manufacturing a base material.

In addition, there is a method of manufacturing a base material for plastic optical fibers whose refractive index changes in the radial direction, and a method of adding a monomer having a high refractive index to the center portion and repeating diffusion and polymerization (Kim Jang-Joo, Shin-Geun, Korea Patent Publication No. 2001 -067464). More specifically, this is as shown in FIGS. 1A and 1B. In FIG. 1A, 21 is a clad and polymerization is completed, and 22 is a state in which a first layer is prepared by adding a monomer mixture having a higher refractive index. In this case, when the monomer mixed solution 23 is added and subjected to a diffusion process and then polymerized, as shown in FIG. 1B, as shown in the refractive index distribution on the right, the monomer mixed solution is diffused to form a layer in which the refractive index gradually changes. However, this method takes a long time for the monomer to diffuse into the polymer, there is a disadvantage that may take a week or more when manufacturing a large diameter base material.

The present invention is to solve the problems of the prior art as described above, in the polymerizing by diffusing the monomer into the polymer in order to induce the refractive index gradient, using a diffusion medium to make the diffusion more easily to manufacture the optical fiber efficiently The purpose is to provide a way to.

That is, the present invention comprises the steps of: (a) injecting one or more monomers into a cylindrical rotary reactor and polymerization under rotation to form a polymer layer on the outer shell of the rotary reactor; (b) injecting a reaction mixture consisting of a diffusion medium, two or more monomers and additives into the cylindrical rotary reactor; (c) polymerizing while dissolving or swelling the polymer layer in a diffusion medium under the rotation of a cylindrical rotary reactor to diffuse the monomer into the polymer; (d) lowering the pressure of the diffusion medium; (e) completing the polymerization reaction; And (f) repeating the steps (b) to (e) until the diameter of the hollow becomes less than or equal to 20% of the diameter of the base material or the hollow disappears. It relates to a method for producing a base material for plastic optical fibers.

Another aspect of the present invention relates to a plastic optical fiber produced by hot stretching a base material for plastic optical fiber produced by the above method.

1A and 1B illustrate a method for manufacturing an optical fiber according to the prior art;

2 is a view showing an example of a rotary reactor used in the present invention,

3 is a phase diagram of carbon dioxide, and

4 is a view showing an example of an apparatus for manufacturing an optical fiber by the manufacturing method of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings and examples.

In the present invention, by forming a refractive index gradient by a method of diffusing a polymer having a high refractive index into the polymer to produce a base material for plastic optical fiber, by using a diffusion medium that can help dispersing the monomer by dissolving or swelling the polymer. It is done.

As the monomer used to manufacture the base material for plastic optical fibers in the present invention, any one known to be conventionally used as an optical material may be used. Specifically, butyl acrylate, methyl methacrylate, benzyl methacrylate, and phenyl methacrylate. Acrylate, 1-methylcyclohexyl methacrylate, cyclohexyl methacrylate, chlorobenzyl methacrylate, 1-phenylethyl methacrylate, 1,2-diphenylethyl methacrylate, diphenylmethyl methacrylate, Perfuryl methacrylate, 1-phenylcyclohexyl methacrylate, pentachlorophenyl methacrylate, pentabromophenyl methacrylate, styrene, TFEMA (2,2,2-trifluoroethyl methacrylate), TFPMA (2,2,3,3-tetrafluoropropylmethacrylate), PFPMA (2,2,3,3,3-pentafluoropropylmethacrylate), HFIPMA (1,1,1,3,3 , 3-hexafluoroy Propyl methacrylate), HFBM (2,2,3,4,4,4-hexafluorobutyl methacrylate), HFBMA (2,2,3,3,4,4,4-heptafluorobutylmetha A kind of monomer selected from the group consisting of acrylate), PFOMA (1H, 1H-perfluoro-n-octyl methacrylate), and DHFOA (1,1-dihydroperfluorooctyl acrylate) or a mixture of two or more monomers may be used.

The monomer is polymerized by UV polymerization or thermal polymerization to form a base material. Therefore, a photoinitiator and / or a thermal polymerization initiator are added as an additive at the time of monomer polymerization.

As a photoinitiator which can be used by this invention, specifically, 4- (para- tolyl thio) benzophenone, 4,4'-bis (dimethylamino) benzophenone, 2-methyl-4'- (methyl cyio) -2-morpholino-propiophenone, 1-hydroxycyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzophenone, 1- [4- ( 2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-benzyl-2-methylamino-1- (4-morpholinophenyl) -butanone- 1, 2,2-dimethoxy-1,2-diphenylmethane-1-one, bis (2,4,6-trimethylbenzoyl) -phenylphosphineoxide, 2-methyl-1 [4- (methylthio ) Phenyl] -2-morpholinopropan-1-one, bis (.eta.5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-py) Ro-1-yl) -phenyl) titanium, and the like, but is not limited thereto.

As the thermal polymerization initiator that can be used in the present invention, specifically, 2,2'-azobis (isobutyronitrile), 1,1'-azo-bis (cyclohexanecarbonitrile), 2,2'-azo Bis (2,4-dimethylvaleronitrile), 2,2'-azobis (methylbutyronitrile), di-tert-butyl peroxide, lauroyl peroxide, benzoyl peroxide, tert-butyl peroxide, Azo-tert-butane, azo-bis-isopropyl, azo-normal-butane, di-tert-butyl peroxide and the like can be exemplified, but is not limited thereto.

On the other hand there is a molecular weight modifier (chain transfer agent) may be added to control the molecular weight of the polymer made of a base material, and as a specific example of n-butyl-far kaeptan, La sound far kaeptan, octyl far kaeptan, dodecyl far kaeptan, 1-butanesium and the like, but is not limited thereto. The molecular weight of the base material can maintain a certain mechanical properties even after being drawn into the optical fiber, and should be a range that can be stretched, the molecular weight range that satisfies this is generally 10,000 ~ 200,000 based on the weight average molecular weight.

In the present invention, first, at least one monomer is partially introduced into a cylindrical rotary reactor, and then polymerized under rotation to form a polymer layer primarily, and then a mixture of two or more monomers having a higher refractive index than the polymer layer is used. The mixture was mixed with a diffusion medium capable of dissolving or swelling, introduced into a cylindrical rotary reactor, and polymerized under rotation to facilitate diffusion of the monomer into the polymer layer. At this time, prior to forming the polymer layer in the cylindrical rotary reactor may be added to form a separate clad layer.

Cylindrical rotary reactor used in the production of the base material preferably uses a structure having a structure as shown in FIG. The cylindrical reactor shown in FIG. 2 is formed of an upper lid 12, a cylinder 13, and a lower stopper 14 having a hole 11 in the center thereof, and is formed to be assembled and detached, thereby completing the production of the base metal. It is then preferable in view of the possibility of collecting and reusing the reactor. However, not limited to this, other reactors suitable for applying the present invention can be used. As the material of the rotary reactor, all materials known in the art that are stable to heat and pressure without contaminating the contents may be used, and in general, a metal material such as sus and aluminum or a plated with chromium and nickel may be used. . In the case of photopolymerization, a transparent material capable of transmitting UV such as glass or quartz is used.

As the diffusion medium, a solvent may be used as the monomer, or a mixture of a solvent and a non-solvent may be used. Specific examples of such diffusion medium include, but are not limited to, supercritical or high pressure fluids such as CO ₂ , SF ₆ , C ₂ H ₆ , CCl ₃ F, CClF ₃ , CHF ₃ , isopropanol, and the like. More preferably supercritical CO ₂ is used. Supercritical carbon dioxide is environmentally friendly, is relatively difficult to supercritical conditions, it dissolves most organic materials and swells most amorphous polymers and is therefore preferred for use as the diffusion medium of the present invention.

The critical temperature and pressure of carbon dioxide are 31.1 ° C. and 72.0 atm, respectively, as shown in the carbon dioxide phase equilibrium diagram of FIG. 3. The temperature and pressure conditions of carbon dioxide useful for the diffusion medium in the present invention vary depending on the polymerization conditions of the polymer. Approximately 10 to 200 ° C. and 70 to 2000 atm, more preferably 60 to 100 ° C. and 70 to 200 atm.

DeSimone et al. (JM DeSimone et al. Science 257, 956 (1992)) have been involved in the synthesis of polymers in supercritical carbon dioxide. However, supercritical polymers such as polystyrene (PS) or polymethylmethacrylate (PMMA) have been developed. In terms of polymerization in carbon dioxide, monomers have good solubility but poor solubility of polymers, so many studies have been conducted on heterogeneous polymerization, and many studies on selecting a suitable stabilizer have been made. (D. E. Betts, et al., In 'High Pressure Chemical Engineering', Ph. R. v. Rohr and Ch. Trepp, Eds. Elsevier, Amsterdam, 1996)

In the present invention, in consideration of the above fact, after the polymerization reaction is performed to a certain degree, the pressure of the diffusion medium is reduced. If the polymerization is continued without lowering the pressure, the solubility of the polymer is lowered, so that precipitation occurs and homogeneous polymerization cannot be achieved. In this case, the timing and speed of lowering the pressure depend on the type of monomer and diffusion medium used, the amount of diffusion medium added, the temperature, the pressure, and the use and stabilizer of the stabilizer.

The mixing ratio of the monomer and the diffusion medium varies depending on the diffusion medium, the type of monomer used, and the additive, but is preferably in the range of 9: 1 to 4: 6 weight ratio, more preferably 8: 2 to 6: 4 weight ratio. . If it is out of the range may cause a problem that precipitation occurs.

In the present invention, the speed of the cylindrical rotary reactor is preferably adjusted in the range of 10 to 10000 rpm. In addition, various adjustments can be made to the rotational speed of the cylindrical reactor to adjust the refractive index distribution. In addition to the simple repetition of rotation and stoppage, it is possible to have a variable speed function such as trigonometric functions with different amplitudes and periods. have.

In addition, in order to prepare a base material having a desired refractive index distribution, not only the temperature and pressure of the diffusion medium may be kept constant, but also the pressure and temperature may be adjusted in the form of a periodic function or an aperiodic function during the process of manufacturing the base material. The base material may be manufactured during the course of movement between a point or two in any phase of weather and weather. In particular, when changing the reaction medium from the liquid phase to the gaseous phase, there is an advantage in maintaining the stability of the morphology of the base material because there is no abrupt phase change when going through the supercritical phase.

On the other hand, during the UV polymerization, the polymerization reaction may proceed while irradiating a UV light source in the form of a pulse for uniform polymerization.

The base material is manufactured by repeating the above steps, that is, mixing the monomers in the diffusion medium and proceeding the polymerization, wherein the base material of the GI-type plastic optical fiber is manufactured by using a monomer having a higher refractive index toward the inside of the base material. can do. At this time, the base material may be manufactured in a form in which the center is completely filled, or may be manufactured in a state in which the hollow is formed in a range where the diameter of the hollow of the center of the base material is 20% or less of the total diameter of the base material.

4 shows an example of an apparatus for producing a base material for plastic optical fibers according to the present invention. The base material manufacturing apparatus includes a cylinder (1) for supplying a reaction medium; A control device 4 capable of monitoring the pressure regulating device 2 and the temperature regulating device 3; A dosing device (5) capable of mixing the monomers with the reaction medium; Cylindrical rotary reactor 6; A drive shaft 7 capable of rotating it; And a heat source or a light source 8 capable of advancing the polymerization of the monomers.

In addition to the structure described above, since the monomer is released in the process of reducing the carbon dioxide pressure, it is possible to further include a device that can react while recycling the monomer.

In the step of acquiring the base material from the cylindrical rotary reactor, if the temperature is slowly lowered in a bath having a device capable of temperature control and ultrasonic or other vibration, the surface between the base material and the rotary reactor may be affected by the difference in the coefficient of thermal expansion. This fall can be obtained to obtain the prepared base material.

In the production of the base material for plastic optical fibers manufactured according to the above-mentioned manufacturing method, in order to facilitate heat transfer for the polymerization reaction, it is generally appropriate to set the radius of the base material to 1 to 10 cm. In addition, the length of the base material is suitably within about 100 cm to be suitable for a conventional thermal drawing process.

The base material for plastic optical fibers manufactured by the present invention is used by converting into a refractive index distributed plastic optical fiber having a desired diameter through a process of thermal drawing. When the hollow is formed inside the base material, the upper part of the base material may be applied with a low pressure of 1 atm or less to the hollow of the base material in order to fill the hollow of the base material during thermal stretching.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are intended to illustrate the present invention and are not intended to limit the present invention.

In the embodiment, a rotary reactor and a manufacturing apparatus of the structure shown in FIGS. 2 and 4 were used. At this time, the diameter of the rotary reactor was 55mm, the length was 300mm, was used to form a cladding layer of 15mm thickness in the cylindrical rotary reactor. Meanwhile, tetrafluoropropyl methacrylate (TFPMA) and trifluoroethyl methacrylate (TFEMA) were used as monomers to prepare a base material having a refractive index change in the radial direction through photopolymerization. (Para-torylcyio) benzophenone (0.02 mol%) was used, and normal-butyl-mercaptan (1-BuSH) was used as a molecular weight regulator. The dosage of the molecular weight modifier may vary slightly between dosing steps, but was generally 0.13% to 0.21% by weight. The monomer was stored in a mixed state with a photoinitiator and a molecular weight regulator. The carbon dioxide used was 99.995% pure and passed through a filter to remove moisture and dust into the base material manufacturing equipment. Since the obtained base material is hollow, it is stretched with an optical fiber of 0.75 mm in diameter with a pressure inside the hollow at 0.2 atm during hot stretching, and then 50 m point by pulse broadening method using a 650 nm pulse laser as a light source. The bandwidth at is measured. At this time, NA of the input pulse was 0.2. For details on bandwidth measurement by the pulse broadening method, see R. Olshansky and D. R. Keck, Appl. Optics, vol. 15, pp. 483-491, 1976.

Example 1:

The composition of the monomer input step by step is shown in Table 1. In the first step, the inside of the base material manufacturing apparatus was fixed at 65 ° C. while irradiating UV constantly, and reacted while rotating at 300 rpm for 24 hours in an argon atmosphere (1 atm) to prepare a polymer layer. From step 2, the polymerization was carried out under supercritical carbon dioxide. The monomer was added as in step 2, but the mixing ratio of monomer and carbon dioxide was 7: 3 by weight, and the pressure was 35 MPa. The polymerization was carried out by irradiating UV pulses while rotating a cylindrical rotary reactor at 300 rpm for 4 hours, and then the polymerization was further performed for 12 hours by lowering the pressure of carbon dioxide to atmospheric pressure. Precipitation did not occur, and each step was repeated under the same conditions to obtain a matrix having a final diameter of 10 mm in diameter, which was thermally stretched to have a bandwidth of 2.1 Gbps for 50 m.

step TFPMA (ml) TFEMA (ml) 1-BuSH (ml) One 390 0 1.22 2 130 38 0.49 3 110 36 0.41 4 90 31 0.32 5 81 29 0.27 6 68 25 0.22 7 59 23 0.19 8 51 20 0.15 9 40 16 0.12 10 21 9 0.06

Example 2:

A base material was prepared under the same conditions as in Example 1, but the base material was prepared at a pressure of carbon dioxide of 100 atm, and a base material having a diameter of about 10 mm was obtained. The bandwidth of the optical fiber manufactured using this was 1.0 Gbps per 50m.

According to the present invention, by using a supercritical or high pressure fluid as a diffusion medium, it is possible to easily diffuse the monomer having a high refractive index, thereby providing a new and improved method for producing a base material for plastic optical fibers.

Claims (13)

(a) adding at least one monomer to a cylindrical rotary reactor and polymerizing under rotation to form a polymer layer on the outer shell of the rotary reactor; (b) injecting a reaction mixture consisting of a diffusion medium, two or more monomers and additives into the cylindrical rotary reactor; (c) polymerizing while dissolving or swelling the polymer layer in a diffusion medium under the rotation of a cylindrical rotary reactor to diffuse the monomer into the polymer; (d) lowering the pressure of the diffusion medium; (e) completing the polymerization reaction; And (f) repeating the steps (b) to (e) until the diameter of the hollow is less than or equal to 20% of the diameter of the base material or the hollow is disappeared. Method for producing a base material for plastic optical fibers. The method of claim 1, wherein as the monomer, methyl methacrylate, benzyl methacrylate, phenyl methacrylate, 1-methylcyclohexyl methacrylate, cyclohexyl methacrylate, chlorobenzyl methacrylate, 1-phenylethyl methacrylate Late, 1,2-diphenylethyl methacrylate, diphenylmethyl methacrylate, perfuryl methacrylate, 1-phenylcyclohexyl methacrylate, pentachlorophenyl methacrylate, pentabromophenyl methacrylate, Styrene, TFEMA (2,2,2-trifluoroethylmethacrylate), TFPMA (2,2,3,3-tetrafluoropropylmethacrylate), PFPMA (2,2,3,3,3- Pentafluoropropylmethacrylate), HFIPMA (1,1,1,3,3,3-hexafluoroisomethacrylate), HFBM (2,2,3,4,4,4-hexafluorobutyl Methacrylate), HFBMA (2,2,3,3,4,4,4-heptafluorobutylmethacrylate), PFOM (1H, 1H-perfluoro-n-octylmethacrylate), And DHFOA (1,1-dihydroperfluorooctyl acrylate). A method of manufacturing a base material for plastic optical fibers, characterized in that using one selected from the group consisting of. The method of manufacturing a base material for plastic optical fiber according to claim 1, wherein a photopolymerization initiator or a thermal polymerization initiator and a molecular weight regulator are mixed as the additive. The method of manufacturing a base material for plastic optical fiber according to claim 1, wherein the polymerization reaction is performed by UV polymerization or thermal polymerization. The method of manufacturing a base material for plastic optical fibers according to claim 1, wherein a material of a solvent or a solvent and a non-solvent is mixed with the monomer as the diffusion medium. The method of claim 1, wherein a supercritical or high pressure fluid of carbon dioxide, SF ₆ , C ₂ H ₆ , CCl ₃ F, CClF ₃ , CHF ₃ , or isopropanol is used as the diffusion medium. Manufacturing method. 7. The method of claim 6, wherein supercritical or high pressure carbon dioxide in the range of 70 to 2000 atm and 10 to 200 DEG C is used as the diffusion medium. The method of manufacturing a base material for plastic optical fiber according to claim 1, wherein the mixing ratio of the monomer and the diffusion medium is adjusted in a weight ratio of 9: 1 to 4: 6. The method of manufacturing a base material for plastic optical fiber according to claim 1, wherein the rotary reactor is rotated at a constant speed or at a constant speed. The method of manufacturing a base material for plastic optical fiber according to claim 1, wherein the pressure and temperature of the reaction medium follow a specific form of change in period, phase and amplitude. The method of claim 1, wherein the temperature and pressure conditions of the diffusion medium are controlled to be maintained in one of a liquid phase, a supercritical phase, a vapor phase, or to move between one or more phases. Method for producing a base material for plastic optical fiber, characterized in that. The method of manufacturing a base material for plastic optical fibers according to claim 1, wherein a change in refractive index in the radial direction of the base material is induced by gradually changing the refractive index of the monomer mixture used in step (b). The plastic optical fiber manufactured by heat-extending the base material for plastic optical fibers manufactured by the method of Claim 1 or 2.