JPH09281348A - Plastic optical fiber - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: The core material is apt to be blocked during polymerization, so that the light is scattered by the block and the transmission loss cannot be reduced. Provided is a plastic optical fiber having a core having a desired refractive index distribution and excellent transmission loss. SOLUTION: The core of a plastic optical fiber in which the refractive index of the core decreases from the center toward the outer diameter method is composed of a plurality of concentric layers, and the resin of each layer is formed by polymerizing a monomer represented by the following general formula. And a hydrogen atom of R ¹ , R ² , R ³ and R ⁴ in the general formula of the monomer so that the refractive index of each layer of the plurality of layers decreases outward from the center. A polymer of monomers having different substitution rates is used, and as the resin for each layer, a polymer of nonafluoroisopropyl acrylate, octafluoroisopropyl acrylate, or heptafluoroisopropyl acrylate is used. CH ₂ CR ¹ COOCR ² R ³ R ⁴ (In the formula, R ^{1 to} R ⁴ are halogen, deuterium or a halogenated alkyl group)

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical fiber having a desired refractive index distribution and excellent transmission loss.

[0002]

2. Description of the Related Art A so-called plastic optical fiber made of plastic as both a core material and a clad material is a glass optical fiber as a short-distance optical transmission line in which transmission loss is not a problem between electronic devices for transmitting and receiving optical signals. It is easy to use and has a low price, so it is widely used. Such plastic optical fiber
It is especially important in the concept of next-generation communication networks such as LAN and ISDN.

FIG. 2 shows a plastic optical fiber.
A step index (SI) type fiber having a refractive index distribution shown in (A) has been put into practical use, but this fiber has a small transmission capacity and is not suitable for communication. For high-speed transmission, it is most desirable to make the refractive index distribution a parabolic shape, but by using the stepwise refractive index distribution shown in Fig. 2 (B), the transmission capacity can be easily increased compared to the SI type. it can. In FIG. 2, 1 indicates the relative magnitude of the refractive index in the core, and 2 indicates the relative magnitude of the refractive index in the clad.

Conventionally, as disclosed in JP-A-2-16505, in order to improve the refractive index distribution, methylmethacrylate and fluoroalkylmethacrylate are used as monomers, and these are polymerized at an appropriate ratio. The method of using the core resin is adopted.

[0005]

However, in this method, since methylmethacrylate and fluoroalkylmethacrylate have different reactivities, they are likely to be blocked, and as a result, it is difficult to reduce transmission loss due to light scattering. is there. The present invention has been made in view of the above problems, and an object thereof is to provide a plastic optical fiber having a desired refractive index distribution and excellent transmission loss.

[0006]

The plastic optical fiber of the present invention comprises a core and a clad layer covering the core,
The core is composed of multiple concentric layers, so that the refractive index of each layer drops from the center toward the outer diameter method,
The resin constituting each layer is a polymer obtained by polymerizing monomers (monomers) having different substitution rates of hydrogen atoms of R ¹ , R ² , R ³ and R ^{4 in} the following general formula.
CH ₂ CR ¹ COOCR ² R ³ R ⁴ (wherein R ^{1 to} R ⁴ are halogen, deuterium or a halogenated alkyl group) The plastic optical fiber of the present invention is used for the polymer constituting the core layer. Can be achieved by using a monomer having less carbon-hydrogen bonds than butyl methacrylate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the resin used for the clad layer of the plastic optical fiber in the present invention, the following resins can be mentioned. Polymers such as decafluoroisopropyl acrylate, isopropyl acrylate, trifluoroethyl acrylate, deuterated fluoroisopropyl acrylate, trifluoroisopropyl acrylate, trifluorobutyl acrylate, tetrafluorobutyl acrylate and pentafluorobutyl acrylate can be used. You may use the same thing as the monomer used as the resin which comprises a core.

The monomer to be the resin constituting the core in the present invention is represented by the above general formula, but R
¹ is a hydrogen atom, one of R ² , R ³ and R ⁴ is a hydrogen atom,
When two of them are methyl groups, they are preferable because they are excellent in polymerizability, and particularly, it is desirable that the halogen atom to be replaced with a hydrogen atom is a fluorine atom because it is excellent in reducing transmission loss.

Core The following compounds can be mentioned as the polymerization initiator used in the present invention. Di-t
-Butyl peroxide, t-butyl hydroperoxide, dicumyl peroxide, cumene hydroperoxide, azobisisobutyronitrile and the like. The amount of the polymerization initiator added is usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the monomer,
It is more preferably 0.1 to 3 parts by weight.

A specific example of the method for producing the plastic optical fiber of the present invention will be described with reference to FIG. Regarding the base material, first, a cylindrical resin that becomes a clad layer by encapsulating a polymer monomer in a rotating cylindrical body (eg, glass container, material is not limited) and polymerizing while rotating. A layer is formed on the inner wall of the cylinder. Next, take out the cylindrical polymer tube 3 to be the clad layer formed,
A monomer containing a polymerization initiator that forms a core is injected therein (FIG. 1 (A)). Then, while rotating, this monomer is polymerized to form the outermost first resin layer 5 constituting the core having a higher refractive index than the clad layer. Next, the monomers 6 having different amounts of hydrogen substitution of the polymer forming the core are injected into the cylindrical first resin layer 5 (FIG. 1 (B)). Then, while rotating, the monomer 6 is polymerized to form a cylindrical second resin layer. By repeating this operation, a base material having a refractive index gradually decreasing from the center to the outside is manufactured (FIG. 1 (C)). The clad layer may be produced by superposing on the inner wall of the cylindrical body while rotating the cylindrical body as described above, or may be produced by making a hole in the rod. The manufacturing method does not matter. Further, the central portion of the core may be produced by polymerization after monomer filling, or may be produced by collapse. To make the fiber base material (preform) produced under the above conditions into a fiber,
For example, the device shown in FIG. 3 can be used. In FIG. 3, the base material 7 is heated and softened in a heating furnace, and one end of the base material 7 is drawn by the winding 11, drawn, and spun to obtain a fiber 9 having a predetermined diameter. At the time of spinning, while controlling the outer diameter by the outer diameter monitor device 10, the rotation speed of the winding 11 is controlled to adjust the draw ratio to obtain a plastic optical fiber having a desired outer diameter.

[0014]

Example 1 Outer diameter 50 mm, inner diameter 40 m obtained by polymerizing degafluoroisopropyl acrylate as a monomer for the cladding layer.
A polymer tube having a length of m and a length of 1000 mm was prepared. In addition,
The dimensions of the polymer tube are the same as those of other examples and comparative examples described later. Then, nonafluoroisopropyl acrylate was injected into the polymer tube to be the clad layer and polymerized at 70 ° C. for 24 hours while rotating to obtain a first resin layer having a thickness of 5 mm on the inner wall of the polymer tube. Further, heptafluoroisopropyl acrylate was injected into the inside and polymerized while rotating to obtain a second resin layer having a thickness of 5 mm on the inner wall of the resin layer. The polymerization initiator used was t-butyl peroxide, and was added in an amount of 0.1 part by weight based on 100 parts by weight of the monomer. Octafluoroisopropyl acrylate was injected into the second resin layer and polymerized at 70 ° C. for 24 hours while rotating to form a resin body having an outer diameter of 5 mm. After that, polymerization was repeated using monomers having different fluorine substitution rates to prepare a plastic optical fiber preform. When the refractive index distribution of the manufactured base material was examined, it was found that the refractive index of the resin body formed the stepwise distribution shown in FIG. 2 (B). 200 base materials prepared
After heating to 0 ° C., drawing and drawing were performed to produce a plastic optical fiber having an outer diameter of 650 μm. When the transmission loss of this manufactured fiber was measured, it was 80d at a wavelength of 650 nm.
B / km. When the transmission band of this fiber was investigated by the pulse method, the wavelength was 100 MHz · km.

Example 2 A polymer tube having an outer diameter of 50 mm prepared by polymerizing isopropyl acrylate as a monomer for the cladding layer was prepared.
Then, while chloroisopropyl acrylate was injected into the polymer tube and rotated, polymerization was carried out at 70 ° C. for 24 hours to form a cylindrical first resin layer serving as a layer constituting the core. Dichloroisopropyl acrylate was injected into the inside and polymerized while rotating to obtain a second resin layer to be the resin of the core. Further, trichloroisopropyl acrylate was injected into the second resin layer, and polymerization was carried out at 70 ° C. for 24 hours while rotating to form a third resin layer. Finally, inject decachloroisopropyl acrylate into the third resin layer and rotate it at 70 ° C for 2
Polymerization was carried out for 4 hours to form a resin body in the central portion to prepare a plastic optical fiber preform. When the refractive index distribution of the prepared base material was examined, the refractive indexes of the first, second and third resin layers and the resin body in the central portion formed the stepwise distribution shown in FIG. 2 (B). I found out. 200 base materials prepared
After heating to 0 ° C., drawing and drawing were performed to produce a plastic optical fiber having an outer diameter of 650 μm. When the transmission loss of the produced plastic optical fiber was measured, the wavelength was 650.
It was 90 dB / km in nm.

Example 3 A polymer tube having an outer diameter of 50 mm prepared by polymerizing isopropyl acrylate as a monomer for the clad layer was prepared.
Then, monobromoisopropyl acrylate was injected into the clad tube and polymerized while rotating to form a 5 mm-thick first resin layer constituting the core. While injecting dibromoisopropyl acrylate into the inside and rotating, it was polymerized at 70 ° C. for 24 hours, and the second layer with a thickness of 5 mm was used.
The resin layer of was created. Next, tribromoisopropyl acrylate was injected into the second resin layer and polymerized while rotating at 70 ° C. for 24 hours to form a resin body having an outer diameter of 5 mm. A plastic optical fiber preform was produced by repeating the polymerization and polymerization. When the refractive index distribution of the prepared base material was examined, the refractive indexes of the first and second resin layers and the resin body in the central portion were
It was found that the stepwise distribution as shown in FIG. 2 (B) was formed. The produced base material was heated at 200 ° C., stretched and drawn to produce a plastic optical fiber having an outer diameter of 650 μm. When the transmission loss of the obtained fiber was measured, it was 110 dB / km at a wavelength of 650 nm. When the transmission band of this fiber was investigated by the pulse method, it was 100 MHz · km at a wavelength of 650 nm. This is S
The value was about 10 times wider than that of the type I fiber.

Comparative Example 1 A tube made of a polymer of trifluoroethyl methacrylate having an outer diameter of 50 mm was prepared as a clad layer, and then,
The first in which methyl methacrylate (10 parts by weight) was dissolved in trifluoroethyl methacrylate (100 parts by weight)
The mixture was poured into the inside of the polymer tube and polymerized at 70 ° C. while rotating to form a cylindrical first resin layer having a thickness of 5 mm. Next, while increasing the concentration of methyl methacrylate in the first resin layer higher than that in the first mixture, this operation was repeated 4 times to form the second, third and fourth resin layers, and the plastic light was formed. A fiber preform was prepared. When the refractive index distribution of the manufactured base material was examined, the refractive index of each resin layer formed the stepwise distribution shown in FIG. 2 (B). The prepared base material was heated at 200 ° C. and drawn to obtain a fiber having an outer diameter of 650 μm, and the transmission loss was measured and found to be 160 dB / km at a wavelength of 650 nm.

Comparative Example 2 As a clad layer, a tube made of a polymer of trifluorobutyl acrylate having an outer diameter of 50 mm was prepared, and then a mixture of trifluorobutyl methacrylate (100 parts by weight) and methyl methacrylate (10 parts by weight) was dissolved. Was injected into the inside of the polymer tube to be the clad layer, and while being rotated, it was polymerized at 70 ° C. for 24 hours to form a first resin layer having a thickness of 5 mm to be the resin layer constituting the core.
Next, the second, third, and fourth mixed solutions in which the concentration of methyl methacrylate was increased by 10 parts by weight were prepared in the first resin layer, and this operation was repeated 4 times to form a core. A plastic optical fiber preform was prepared. When the refractive index distribution of the prepared base material was examined, the first, second, third and fourth refractive indexes formed the stepwise distribution shown in FIG. 2 (B). The produced base material was heated and drawn to form a fiber having an outer diameter of 650 μm, and the transmission loss was measured and found to be 170 dB / km at a wavelength of 650 nm.

Comparative Example 3 A tube made of a polymer of trifluoropropyl acrylate having an outer diameter of 50 mm to be a clad layer was prepared.
A mixture prepared by dissolving methyl methacrylate (10 parts by weight) in trifluoropropyl arylate (100 parts by weight) was poured into the inside of the polymer tube serving as the clad layer and polymerized at 70 ° C. while rotating to give a 5 mm thick film. A cylindrical first resin layer was formed. Next, the second, third, and fourth mixed liquids in which the concentration of methyl methacrylate was increased by 10 parts by weight were prepared, and the above operation was repeated four times, and the first, second (thickness 5 mm), A plastic optical fiber preform was prepared by forming a core portion composed of 3 (thickness 5 mm) and fourth (thickness 5 mm) resin layers. When the refractive index distribution of the manufactured base material was examined, the refractive index of each resin layer formed the stepwise distribution shown in FIG. 2 (B). The prepared base material was drawn into a fiber with an outer diameter of 650 μm, and the transmission loss was measured. The wavelength was 650 nm.
Was 170 dB / km.

[0020]

As described above, in the plastic optical fiber according to the present invention, the core is composed of a plurality of layers, and the resin of each layer uses a composition in which a specific monomer is polymerized (in particular, a fluorine-based polymer). As a result, it has a desired refractive index distribution and excellent transmission characteristics.

[Brief description of drawings]

FIG. 1A is a perspective view showing a step of injecting a first mixed liquid to be the outermost first resin layer of a core into a polymer tube to be a clad layer. B: Second cylindrical resin layer on second cylindrical resin layer
FIG. 6 is a perspective view showing a step of injecting the mixed solution of C: A perspective view of a base material of a plastic optical fiber according to the present invention.

FIG. 2A is a diagram showing a refractive index distribution in which the core of a plastic optical fiber is SI type. B: A diagram showing a refractive index distribution in which a change in the refractive index of each layer of the core is stepwise.

FIG. 3 is a schematic view of a plastic optical fiber drawing device.

[Explanation of symbols]

 1 core 2 clad 3 polymer tube to be a clad layer 4 monomer to be a first resin layer 5 first resin layer 6 monomer to be a second resin layer 7 base material of plastic optical fiber 8 heating furnace 9 plastic optical fiber 10 Outside diameter monitor device 11 Winding

Claims (2)

[Claims] 1. A core comprising a core and a clad layer covering the outer periphery of the core, the core being composed of a plurality of concentric layers, and the resin of each layer being formed by polymerizing a monomer represented by the following general formula. In order to decrease the refractive index of each layer of the plurality of layers from the center to the outside, the substitution ratio of R ¹ , R ² , R ³ and R ⁴ in the general formula of the monomer to hydrogen atoms is composed of a united structure. Plastic optical fiber that is different. CH ₂ CR ¹ COOCR ² R ³ R ⁴ (In the formula, R ^{1 to} R ⁴ are halogen, deuterium or a halogenated alkyl group) 2. The resin of each layer constituting the core is defined by claim 1.
In the general formula described in ¹ , R ¹ is a hydrogen atom, R ² , R ³ ,
The plastic optical fiber according to claim 1, wherein one of R ⁴ is a hydrogen atom and two are polymers of a monomer having a methyl group.