KR20050025806A - Graded index polymer optical fiber preform and fabrication method thereof - Google Patents

Abstract

A graded-index polymer optical fiber preform and a manufacturing method thereof are provided to improve bandwidth property by employing a concentric arrangement multilayer structure using a plurality of thin polymer tubes. A plurality of polymer tubes(10,11,12) and a polymer tube(20) form a concentric arrangement multilayer structure. Each of the polymer tubes(10,11,12) has a different refractive index and diameter. The polymer tube(20) disposed on a center of an optical fiber has a highest refractive index. A monomer mixed solution is filled in a space between the polymer tubes(10,11,12) so that a graded-index is realized. Each of the polymer tubes(10,11,12) is manufactured from a copolymer of two monomers having different refractive index.

Description

Refractive index distribution polymer fiber base material and its manufacturing method {GRADED INDEX POLYMER OPTICAL FIBER PREFORM AND FABRICATION METHOD THEREOF}

The present invention relates to a refractive index distribution polymer optical fiber base material having a broadband characteristic and a method of manufacturing the same.

Polymer optical fiber is attracting attention as it is installed in a place where silica optical fiber is difficult to apply because it exhibits complementary characteristics compared to that of conventional silica optical fiber.

The raw material of the polymer optical fiber is poly (methyl methacrylate) [PMMA], polycarbonate (PC), polystyrene (PS), CR-39, Arton, Norbonen and transmission loss with excellent optical properties. Deuterium-substituted PMMA, partially fluorine-substituted polymers, and all-fluorine-substituted polymers have been studied. Until now, relatively good PMMA systems have been used with optical transmittance of 93%.

Various methods for manufacturing the polymer optical fiber have been proposed, but can be classified into unit extrusion, continuous extrusion, and base material extraction. As a method for manufacturing a broadband polymer optical fiber for ultra-high speed information communication, a base material drawing method that can reduce transmission loss by reducing the possibility of mixing foreign substances is mainly applied. At this time, in order to improve the band characteristics, the radial refractive index distribution (Graded Index) is given to the inside of the base material during the process of manufacturing the base material and withdraw it, so that the radial refractive index distribution of the optical fiber decreases sequentially from the center to the outer peripheral part. A refractive index polymer optical fiber (hereinafter referred to as GI type POF) is manufactured and used. The GI-type POF has superior band characteristics compared to single-index polymer fibers, and shows suitable properties for application of polymer fibers.

In order to improve the refractive loss or coupling loss with the light source, the GI type POF should be designed so that the numerical aperture (NA) is large and the transmission loss is as small as possible. In order to increase NA, the difference between the maximum refractive index Δn between the center and the outer circumference of the GI type POF should be large.

NA generally has a value of about 0.2 to 0.5 and is a value expressed by the following formula.

Equation 1: NA = n ₀ sinθ _max = sinθ _max =

In the above formula, n ₀ represents the refractive index of the cladding, n ₁ represents the refractive index of the core center portion, n ₂ represents the refractive index of the core peripheral portion, and θ _max represents the maximum light receiving angle. However, since the isotropic light scattering loss of the copolymer tends to be larger as the difference Δn of the refractive index is larger, it is important to select a combination of copolymers so that the difference in refractive index of each of the homopolymers is determined at about 0.03 to 0.01. Do.

In addition, in order to further improve the band characteristics of the GI type POF, the shape of the refractive index distribution also plays a very important factor because the speed between groups is determined by the shape of the refractive index distribution. The refractive index distribution from the center to the outer circumferential surface is expressed by the following equation.

Equation 2: n (r) = n _core (1-Δ (r / a) ^α ) ^1/2

In the above formula, Δ: (n _core ² -n _clad ² ) / n _core ²

r: core radius at any position

a: core radius

α: Profile shape parameter.

When the values of n _core , n _clad and a are determined by the above equation, the ideal refractive index distribution shape can be determined. For example, when α = 1, a refractive index distribution of a triangular structure is obtained, and when α = ∞, a stepped refractive index is used, and when α = 1.5 to 3, a parabolic refractive index distribution is used. 2 shows a state in which the refractive index distribution changes depending on the α value.

The optimum Δ and α values are selected according to the aperture (50-1000 μm) of the POF to be produced. At this time, since the band characteristic largely depends on the value of α, it is very important to design the value of α so that the band characteristic is maximized. It is known that the following relationship is established between the impulse response H (τ) and α, which is a value directly related to the size of the transmission band (where T is a value indicating an impulse response delay time from the highest order to the lowest order mode). ).

if α ≠ 2

H (τ) = "(α + 2) / α" · "τ ^{α / 2} / T ^{(α + 2) / α} ]

Provided that T = (NI / C) Δ · [(α-2) / (α + 2)]

if α = 2

H (τ) = "1 / T]

However, T = (NI / C) · (Δ 2/2)

In addition, the α value that enables the maximum transmission band is expressed by the following equation:

α _opt = 2 + 2.4Δ

Therefore, by setting the value of Δ, α _opt can be obtained. In the general wavelength range of use, the α value is between 1.8 and 2.3. When Δ = 0.01, the optimum α value and the single refraction α value (α = ∞) are calculated by applying the above equation, and the group retardation is about Δ / 2 and the group retardation is about 1/200 times the single refraction value. This means that the input signal waveform remains the same.

Among such GI type POF manufacturing methods, various base material manufacturing methods have been proposed in the base material drawing method. As some representative examples, (1) a method in which a mixture of two different monomers having different reactivity ratios and refractive indices in homopolymerization is put into a reactor and the refractive index distribution is given by the reactivity ratio (Japanese Patent Application Laid-Open No. 61-130904). ; (2) Interfacial-gel effect and selection with a polymer tube by first preparing a polymer tube with excellent optical properties and then preparing a mixture of non-reactive dopants and monomers with properties similar to those in the polymer tube. A method of controlling the refractive index distribution of the central part by the theory of selective diffusion (Korean Patent No. 0170358); (3) winding and laminating a film composed of copolymers having different composition ratios to a core material, followed by heating and stretching the laminate (Japanese Patent No. 1-265208), (4) arranging several polymer layers in concentric circles. A method of drawing an optical fiber (US Pat. No. 5,235,660), and the like, and several other methods are proposed.

The above method has its own advantages, but in the case of (1) and (2), the refractive index distribution is given depending on the polymer polymerization reaction itself, and thus it is difficult to secure reproducibility, and it is difficult to secure an optimal distribution. The polymerization of styrene and methyl methacrylate produced by the method of (3) is difficult because the polymer in the center is polymerized at once and the polymerization heat is severely generated, thus making it difficult to manufacture a large base material and securing productivity. The GI type POF made of coalescing or the like has a very large refractive index difference between the copolymers of adjacent layers of multi-layered fibers such as 0.02 and the like. In this case, it is vulnerable to transmission loss due to the incorporation of foreign matter by continuous spinning and the refraction distribution is continuous during cooling and heating. Difficult to occur, and so that light scattering occurs between the layer and the layer, it has been pointed out that there is a problem in most of the way.

As a result of repeated studies to solve the above problems, the inventors of the present invention, in the manufacturing of the polymer optical fiber base material, which is a preliminary step for manufacturing the polymer optical fiber, the distribution of the refractive index inside the base material from the center to the outer circumference to realize the broadband characteristics The inventors have invented a technology that can give the refractive index gradient characteristic to be continuously lowered and control it effectively.

SUMMARY OF THE INVENTION An object of the present invention is to provide a refractive index distribution type polymer optical fiber base material in which the refractive index distribution in the radial direction is sequentially reduced from the center to the outer circumferential portion, thereby improving the band characteristics.

Still another object of the present invention is to provide a method of manufacturing the refractive index distribution polymer optical fiber base material as described above.

The present invention relates to a refractive index distribution-type polymer optical fiber base material and a method of manufacturing the same, in which the refractive index distribution in the radial direction is sequentially reduced from the center toward the outer circumference thereof, thereby improving the band characteristic.

The polymer optical fiber base material according to the present invention is characterized by the fact that the refractive index gradient is given and effectively controlled so that the distribution of the refractive index therein is continuously lowered from the center toward the outer circumferential portion, thereby implementing broadband characteristics. In addition, the conventional method is difficult to control the refractive index distribution due to the difference in the reactivity ratio or the molecular size, etc., the method of manufacturing a polymer optical fiber base material according to the present invention using a plurality of polymer polymerization tubes having a different refractive index and diameter distribution The α value of is controlled to the optimum value, and the monomer mixture designed to have the median of the refractive indexes of the polymerized tubes is filled between the polymerized tubes and the polymerized tubes so that the swelling and the diffusion occur simultaneously. It is possible to allow the refractive index distribution to change continuously.

First, the present invention includes two or more tubular polymeric polymer tubes having different refractive indices and diameters and smaller diameters, having a higher refractive index, in a concentric arrangement, and including a polymer rod having the highest refractive index in the center thereof. Filling the monomer mixture with the mixing ratio designed to have the median refractive index of the polymer polymer tubes adjacent to the spaces between them, the contiguous multi-layer structure with improved refractive index and continuous band distribution decreased from the center to the outer peripheral part Refractive index distribution type | mold relates to a polymeric optical fiber base material.

The polymer polymerization tube is made from a copolymer of two or more monomers having different refractive indices, and the mixing ratio between the two or more monomers is adjusted to have a desired refractive index. In addition, the monomer mixture is composed of two or more monomers having different refractive indices, and are mixed in a mixing ratio designed to obtain a polymer having a refractive index of the median of two adjacent polymer polymer tube refractive indexes. The monomer mixture is sufficiently swollen by intermolecular diffusion between polymer polymerization tubes, and then polymerized into a polymer having a refractive index distribution that varies gently between the refractive indices of the adjacent polymer polymerization tubes.

In addition, the present invention,

By copolymerizing two or more monomers having different refractive indices, a copolymer having various refractive indices is prepared, and two or more polymer polymer tubes are prepared using the copolymer to have a larger diameter as the refractive index is smaller. Using a copolymer having a large refractive index to produce a polymer rod having a diameter less than or equal to the inner diameter of the smallest polymer tube among the polymer polymer tubes,

The polymer polymerization tubes are sequentially concentrically arranged such that the refractive index decreases toward the outer periphery of the polymer rods,

And filling the monomer mixture designed to have a refractive index of the median refractive index of two polymer polymer tubes refractive index adjacent to the space between the polymer polymer tubes, swelling sufficiently by intermolecular diffusion, and then completing the polymerization.

The present invention relates to a method for manufacturing a refractive index distribution type polymer optical fiber base material of a concentric alignment multilayer structure having a continuous refractive index distribution that decreases from a central portion to an outer circumference and an improved band characteristic.

Looking at the polymer optical fiber base material of the present invention and its manufacturing method in more detail as follows:

The polymer polymerization tube used in the present invention can be obtained from a copolymer of two or more monomers. The copolymerization reaction may be by thermal polymerization or photopolymerization. Examples of the copolymer used in the polymer polymerization tube include fluorine-containing methacrylate copolymers, fluorine-containing methacrylate-methacrylate ester copolymers, and α-fluoromethacrylate copolymers. In an embodiment of the present invention, the monomer of the copolymer is 2,2,2-trifluoro methacrylate, methyl methacrylate, 4-methylcyclohexyl methacrylate, cyclohexyl methacrylate, fluoropryl meta It can be selected from the group consisting of methacrylates such as acrylate, phenylethyl methacrylate, phenylcyclohexyl methacrylate, benzyl methacrylate and phenyl methacrylate, and in order to lower the wavelength loss, Fluorine or chlorine substituents can be used. Materials that can be used as monomers in the present invention and their refractive indices and solubility indices are shown in Table 1 below.

Monomer Refractive Index (Polymer) Solubility Index (δ) 2,2,2-trifluoro methacrylate 1.420 7.8 Methyl methacrylate 1.492 9.2 4-methylcyclohexyl methacrylate 1.4975 9.16 Cyclohexyl methacrylate 1.5066 9.04 Florofyl methacrylate 1.5381 9.93 Phenylethyl methacrylate 1.5487 9.29 Phenylcyclohexyl methacrylate 1.5645 8.91 Benzyl methacrylate 1.5680 9.54 Phenyl methacrylate 1.5706 9.65

Solubility Index: (cal / cm ³ ) ^1/2

Among the monomers described above, it is preferable to select and use a material having the best miscibility due to copolymerization and suppressing phase separation as much as possible.

At this time, the diameter and refractive index of each polymer tube are designed so that an optimum value of α is obtained according to the following Equation 2:

Equation 2: n (r) = n _core (1-Δ (r / a) ^α ) ^1/2

In the above formula,

Δ: (n _core ² -n _clad ² ) / n _core ²

n _core : center refractive index

n _clad : outermost refractive index

n (r): refractive index at any position

r: distance from the center to an arbitrary location

a: full radius

α: Profile shape parameter.

As shown in FIG. 2, the refractive index distribution is triangular in the case of α = 1, the stepped refractive index in the case of α = ∞, and the parabolic refractive index distribution in the case of α = 1.5 to 3 (see FIG. 2). As can be seen in Figure 3, there is an α value that can obtain the maximum bandwidth (band-width) according to the wavelength used. The ideal refractive index distribution shape can be determined by determining an appropriate value of α different from the wavelength used and determining the values of n _core , n _clad and a so that the value of α is obtained by Equation 2. In this way, the diameter and refractive index of each polymer tube can be determined such that a desired refractive index distribution, that is, a desired α value is obtained.

At this time, the refractive index of the polymer polymerization tube can be adjusted to a desired value by changing the type of the monomers used and the mixing ratio between them. After selecting any two or more monomers, the known additive rules are used to determine the mixing ratio between the two or more monomers in which the desired refractive index can be obtained. After mixing and copolymerizing the monomers prepared in this way, it is prepared as a polymer tube of a tube having a diameter obtained by the above formula. At this time, the refractive index of the polymer polymerization tube may be further adjusted by adding an appropriate dopant. As the dopant, diphenyl sulfide, triphenyl sulfide, bromobenzene, bromonaphthalene, benzyl-n-butyl phthalate, and the like may be used, but the present invention is not limited thereto, and the glass transition temperature and molecular weight may vary depending on the amount of the dopant. As such, it is preferable to use in the range of about 0.1 to 20 wt%.

In the production of the polymer polymer tube as described above, the polymer tube to be located on the central portion is designed to have a small diameter and a high refractive index, and gradually increase the diameter to design a low refractive index to produce a plurality of polymer tubes. The tubular polymer tube of the present invention uses a batch method to strictly control the incorporation of external foreign matters and reduce transmission loss as much as possible, and does not apply a continuous extrusion method in which foreign matters are likely to be mixed. desirable. In addition, it is preferable to use a polymerization method using a centrifugal force in which the centrifugal force is imparted by rotating a reactor capable of irradiating heating or light or a reactor capable of heating polymerization around a horizontal axis among the batch methods (see FIG. 4). ). In this case, the faster the rotation speed is, the faster the instrument allows, and the centrifugal force is attached to the reactor wall than the force (F = mg) (m: monomer weight, g: gravity acceleration) to fall by gravity in the cylindrical reactor. The force (F = mrω ² ) (m: monomer weight, r: reactor diameter, ω = angular velocity) should be calculated precisely according to the reactor diameter and monomer weight. In an embodiment of the present invention, the rotation speed may be about 10,000 to 20,000 rpm, and generally about 50 rpm or more is preferred.

As such, when the reactor is rotated about the horizontal axis, the monomer is concentrated on the outer wall by the centrifugal force inside the reactor, and polymerization of the monomers occurs by light irradiation or external heating, thereby producing a tubular polymer polymerization tube. At this time, by using a reactor having a different size, it is possible to produce a polymer polymerization tube of various diameters. On the other hand, when the polymerization reactor is rotated about a vertical axis, there is a possibility that the thickness of the upper and lower tubes may be changed under the influence of gravity, and thus change in transmission characteristics is not preferable. Therefore, in the production of the polymer polymerization tube according to the present invention, the polymerization reactor is rotated about the horizontal axis so that there is no difference in the vertical diameter of the produced tubular polymerization tube.

Prior to the polymerization reaction, it is desirable to purify the polymerization raw material under reduced pressure to maintain high purity. In addition, in order to control the polymerization rate, it is important to precisely measure and add a chain transfer agent, and select and add an appropriate photo initiator or thermal initiator. In an embodiment of the present invention, methane such as n-butyl methane, dodecyl methane and the like are used as the molecular weight modifier, 4,4-bis (dimethylamino) benzophenone and the like are used as the photoinitiator, and AIBN is the thermal initiator. Peroxides such as (2,2-azo-bis (isobutylonitrile)) and BPO (benzoyl peroxide) may be used, but are not limited thereto, and all molecular weights known in the art to which the present invention pertains. Modulators, photoinitiators or thermal initiators can all be used. The molecular weight modifier and the photoinitiator or thermal initiator are added to the monomer in the liquid state by taking about 0.001 to 0.5 wt%, respectively, using a precision balance and then stirred to dissolve sufficiently.

As described above, after the production of a plurality of polymer polymer tubes having different diameters and refractive indices, the diameter gradually decreases and the refractive index increases in the polymer tube having the largest diameter and the lowest refractive index in a strictly controlled clean space. After inserting the polymerization tube in order, the polymerization rod with the highest refractive index is mounted at the center part.

The manufacturing technology of the optical fiber base material according to the present invention is filled with a monomer mixture designed to have a median refractive index between the polymerization tube and the polymerization tube, unlike the existing similar method in order to give a perfect refractive index distribution, and by the monomer mixture It is characterized by the intermolecular diffusion. More specifically, after mounting each of the polymerization tubes, between the polymerization tube and the polymerization tube, a monomer mixture containing two or more monomers having different refractive indices in a mixing ratio designed to have a refractive index of the median of two adjacent polymerization tube refractive indices To fill. The monomers are 2,2,2-trifluoro methacrylate, methyl methacrylate, 4-methylcyclohexyl methacrylate, cyclohexyl methacrylate, fluoropryl methacrylate, phenylethyl methacrylate, phenylcyclo Hexyl methacrylate, benzyl methacrylate and phenyl methacrylate and fluorine or chlorine substituents of these monomers can be selected and used. The refractive index of the monomer mixture is adjusted to a desired value by determining the mixing ratio by a conventional method such as the law of addition in consideration of the refractive index of two or more monomers having different refractive indices selected. At this time, as described above, a dopant may be added to further adjust the refractive index of the monomer mixture, and as such dopants usable, diphenylsulfide, triphenylsulfide, bromobenzene, bromonaphthalene, benzyl-n-butyl Phthalates, and the like, but is not limited thereto, and is preferably used in the range of about 0.1 to 20 wt%.

After that, if it is maintained for a long time at a temperature at which the polymerization reaction does not occur suddenly (for example, about 40 to 60 ° C.), molecular diffusion and swelling occur, and the refractive index of the monomer mixture is between the refractive indexes of two adjacent polymer polymerization tubes. It is distributed with a gentle slope at. That is, the discontinuous refractive index distribution between the interfaces of the polymerized polymer tubes is changed into a smooth and continuous distribution by the intermolecular diffusion through the monomer mixture having the median of these refractive indices. When such a refractive index distribution is obtained, the temperature is raised to complete the polymerization reaction. For example, the polymerization may be completed by raising the temperature to about 60 to 80 ℃. After the polymerization reaction is completed, sufficient post curing is performed using a heat treatment technique under reduced pressure. for example, The unreacted monomer may be removed by performing post-treatment for at least 24 hours while maintaining a temperature of about 70 to 100 ° C. in a vacuum chamber maintained at a pressure lower than atmospheric pressure.

In the present invention, the combination of two or more monomers selected for the production of each monomer mixture liquid filled in the plurality of polymerization tubes having different refractive index and diameter and the space therebetween is equal to each other between the plurality of polymerization tubes and the monomer mixture liquid or Or although it is different or does not matter, it is preferable to combine in consideration of the loss of light scattering.

Hereinafter, the present invention will be described in more detail with reference to examples, which are merely intended to help the understanding by expressing the spirit of the present invention in more detail, and the scope of the present invention is not limited to these examples. Various modifications are possible to those skilled in the art without departing from the gist of the invention.

Example

The refractive index simulation for the wavelength used is designed to design the refractive index distribution in the center and periphery. The value of the refractive index distribution considering the DMD and the like of 1.3 μm wavelength to be used was calculated as 1.982. To this end, the central refractive index of the optical fiber base material to be manufactured was 1.510, the outermost refractive index was 1.493, and the difference between the central and outermost refractive index was 0.017.

In order to maintain the purity of the monomer, vacuum decompression purification was carried out on the raw material of the optical fiber base material, and the central rod had 70 mol% of methyl methacrylate having a refractive index of 1.492 and phenylethyl methacrylate having a refractive index of 1.5487 in order to have the central refractive index. A monomer mixture comprising mol% was prepared, and 0.017 wt% of benzoyl peroxide and 0.005 wt% of a molecular weight modifier were added as a polymerization initiator, and a copolymer polymerization rod having a diameter of 20 mm and a length of 1000 mm was used in a temperature-programmable oven. Was prepared.

In the outermost polymerization tube, the mixing ratio of methyl methacrylate and phenylethyl methacrylate was determined to have a refractive index of 1.493 by the above method, and 0.017 wt% of benzoyl peroxide and 0.005 wt% of a molecular weight regulator were added as a polymerization initiator. In an oven having a temperature programming, the outer diameter was 300 mm, the length was 1000 mm, and the thickness was 10 mm.

The optical fiber base material is designed such that a total of six polymer tubes are positioned between the center rod and the outermost polymer tube, and the six polymer tubes have a height of 1000 mm and a thickness of 10 mm, and the diameters are 260 mm and 220 mm, respectively. , 180 mm, 140 mm, 100 mm, 60 mm, and the refractive index difference (nn _core ) of the center and the corresponding position was prepared to be 0.0100, 0.0080, 0.0040, 0.0020, 0.0015, 0.0000, respectively.

After the polymerization tubes prepared as described above are concentrically aligned with respect to the polymerization rods while maintaining cleanliness, a monomer mixture solution designed to have an intermediate value of the refractive index of the polymerization rods adjacent to each of the polymerization tubes is injected. At this time, the mixing ratio of the monomer mixture is a refractive index difference nn _core is 0.0140, 0.0090, 0.0060, respectively when the polymer in consideration of the refractive index change generated when the mixed liquid phase changes to a solid as described above Design to be 0.0015, 0.0000. Then, the polymer polymerization tube and the monomer mixture were held at 60 ° C. for 24 hours to sufficiently swell, and then cured in an oven capable of temperature control. A polymer optical fiber base material was prepared. The prepared optical fiber base material was vacuum dried in a vacuum oven maintained at 100 ° C. for at least 48 hours to remove residual moisture and monomers, and then mounted on a cutting line device to draw the optical fiber.

As described above, in the prior art, it is virtually impossible to control the refractive index distribution formed by the chemical reaction to an optimal α value, but according to the method of the present invention, a plurality of polymer tubes having accurately designed refractive indices are used. Therefore, it is possible to form an accurate refractive index distribution according to the step from the center to the circumferential direction. In addition, the existing method has to use a bulk polymerization method to lower the transmission loss, it is virtually impossible to manufacture a large base material, it is difficult to control the polymerization rate, so that bubbles are generated inside the polymerization base material to be defective or to control the polymerization rate. Since the molecular weight modifier had to be added, further transmission loss occurred. However, according to the method according to the present invention, the use of a plurality of thin polymer tubes continuously controls the refractive index distribution, and since a small amount of monomer is required between the polymer tubes and the polymer tubes, polymerization heat generation can be suppressed and large The base material can be manufactured. In addition, the method according to the present invention can use a copolymerization method, there is an advantage that it is easy to secure thermal stability, there is an advantage that can be easily produced SI type base material according to the arrangement of the refractive index of the multi-stage polymerization tube.

 1 is a schematic diagram of a refractive index distribution-type polymer optical fiber base material of a multilayer structure obtained by a multi-stage molecular diffusion polymer tube method according to the present invention, wherein polymer tubes having different diameters and refractive indices of the same length are provided in multiple layers on a concentric axis. The central part shows the highest refractive index polymer rod installed.

FIG. 2 shows the dependence of the core portion refractive index distribution, which shows a triangular structure when α = 1, a stepped refractive index structure when α = ∞, and a quadratic distribution near α = 2. .

3 is a graph showing that there is an α value that can obtain the maximum bandwidth according to the wavelength used.

Figure 4 is a schematic diagram of a polymerization method by a horizontal axis centrifugal force vessel for obtaining a polymerization tube according to the present invention, it shows that the use of the horizontal axis is a gravity term is eliminated can obtain a polymerization tube of the same diameter.

Figure 5 is a schematic diagram of the polymerization tube arrangement according to the present invention, it shows that the tubular polymer tube having a different diameter and refractive index is arranged in multiple concentric circles.

FIG. 6 shows the filling of a monomer mixture liquid designed to have a median refractive index of two polymer tubes in an empty space between the polymer tube and the polymer tube.

Figure 7a shows that the difference in refractive index between the polymerization tube and the filling monomer mixture is gentle by molecular diffusion, 7b shows that the polymer of the refractive index distribution is obtained when the polymerization is completed.

8 is a schematic diagram showing the refractive index of the polymer tubes constituting the multi-layer optical fiber base material, (a) shows the refractive index of each polymer tube before the polymerization, (b) is continuous by polymerization by the method of the present invention It is shown that a polymer having a refractive index distribution can be obtained.

*** Description of the main parts of the drawing ***

10: copolymer tube with refractive index n _n

10-1: monomer mixture having refractive index between n _n and n _n-1

10-2: Refractive index distribution at interface due to molecular diffusion

11: copolymer tube with refractive index n _n-1

12: copolymer tube with refractive index n _n-2

20: copolymer tube with refractive index n ₀

30: polymerization reactor in which monomers can react

31: motor to rotate the polymerization reactor

40: Schematic diagram of the refractive index distribution after polymerization

50: refractive index distribution of discontinuous tubes

60: matrix of continuous refractive index distribution after reaction

Claims (13)

The smaller the diameter and the smaller the diameter, the concentric alignment of two or more polymer polymer tubes having a high refractive index, the polymer rod having the highest refractive index in the center, and adjacent to the space between the polymer polymer tubes A polymer optical fiber matrix having a continuous refractive index distribution of a concentric alignment multilayer structure having a continuous refractive index distribution that decreases from the center portion to an outer circumferential portion and improving band characteristics by filling a monomer mixture having a median refractive index of the polymer polymerization tubes. The method of claim 1, wherein the polymer polymer tube is made of a copolymer of two or more monomers having different refractive index, and the mixing ratio between the two or more monomers is controlled, whereby the polymer polymer tube has a desired refractive index. Polymer optical fiber base material. The method of claim 1, wherein the monomer mixture is composed of two or more monomers having different refractive indices, and the mixing ratio between the two or more monomers to obtain a polymer having a refractive index of the median of two polymer polymer tube refractive indexes adjacent to each other And wherein the monomer mixture is polymerized at the same time as the intermolecular diffusion between the polymer polymerization tubes and is present as a polymer having a refractive index distribution that varies gently between the refractive indices of the adjacent polymer polymerization tubes. The method of claim 2 or 3, wherein the monomer is 2,2,2-trifluoro methacrylate, methyl methacrylate, 4-methylcyclohexyl methacrylate, cyclohexyl methacrylate, fluoroprime methacrylate A polymeric optical fiber base material selected from the group consisting of latex, phenylethyl methacrylate, phenylcyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, and fluorine or chlorine substituents thereof. The polymer optical fiber base material according to any one of claims 2 to 4, wherein a refractive index of the polymer polymerization tube or the monomer mixture is further controlled by a dopant. 6. The method of claim 5, wherein the dopant is selected from the group consisting of diphenylsulfide, triphenylsulfide, bromobenzene, bromonaphthalene and benzyl-n-butyl phthalate, and is used in the range of 0.1 to 20 wt%. Polymer optical fiber base material. By copolymerizing two or more monomers having different refractive indices, a copolymer having various refractive indices is prepared, and two or more polymer polymer tubes are prepared using the copolymer to have a larger diameter as the refractive index is smaller. Using a copolymer having a large refractive index to produce a polymer rod having a diameter less than or equal to the inner diameter of the smallest polymer tube among the polymer polymer tubes, The polymer polymerization tubes are sequentially concentrically arranged such that the refractive index decreases toward the outer periphery of the polymer rods, And filling the monomer mixture liquid designed to have a refractive index of a median refractive index of two polymer polymer tube refractive indexes adjacent to the space between the polymer polymer tubes, swelling sufficiently by intermolecular diffusion, and then polymerizing. A method of manufacturing a refractive index distribution polymer fiber base material having a concentric alignment multilayer structure having a continuous refractive index distribution that decreases from a central portion to an outer circumference and an improved band characteristic. The method of claim 7, wherein the polymer polymer tube is controlled to have a desired refractive index by adjusting a mixing ratio between two or more monomers having different refractive indices. 8. The method of claim 7, wherein the monomer is 2,2,2-trifluoro methacrylate, methyl methacrylate, 4-methylcyclohexyl methacrylate, cyclohexyl methacrylate, fluoropryl methacrylate, phenylethyl Methacrylate, phenylcyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate and a chlorine or fluorine substituent thereof. 10. The method according to any one of claims 7 to 9, wherein a dopant is added during the production of the polymer polymer tube to further adjust the polymer polymer tube to have a desired refractive index. The method according to claim 10, wherein the dopant is selected from the group consisting of diphenyl sulfide, triphenyl sulfide, bromobenzene, bromonaphthalene and benzyl-n-butyl phthalate within the range of 0.1 to 20 wt%. How to. 8. The method of claim 7, wherein the polymer polymerization tube is manufactured in a batch manner in which the reactor is rotated about a horizontal axis to impart centrifugal force, thereby preventing the incorporation of foreign foreign substances and reducing the transmission loss, and the obtained polymerization tube has a constant thickness up and down. Characterized in that it has a. 13. The method of claim 12, wherein the rotational speed of the reactor is at least 50 rpm.