JPH0713030A - Method and apparatus for producing plastic optical fiber preform - Google Patents

Abstract

PURPOSE:To provide the method and apparatus for producing the plastic optical fiber preform. CONSTITUTION:Initial raw material vapor having a low refractive index is produced by using a polymer A (refractive index: Na) and a compd. having the refractive index different from the refractive index of this polymer A in the process for production of the plastic optical fiber preform by depositing gaseous materials on the inner surface of a hollow cylindrical body rotating around its axis by a CVD(Chemical Vapor Deposition) method. A hollow cylindrical body 11 of the same compsn. is produced and the initial raw material vapor having a low refractive index is deposited on the inside surface of this hollow cylindrical body 11 via a nozzle 12. The compounding ratio of the compds. to be compounded in the raw material vapor is changed at every repetition of this deposition, by which the refractive index is successively increase. The refractive index distribution in which the refractive index is successively lowered from the center to the outside diametral direction on the optical fiber preform is thus formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a plastic optical fiber preform.

[0002]

2. Description of the Related Art An optical fiber having both a core and a clad made of plastic is used as a short-distance optical transmission line in which transmission loss is not a problem between electronic devices for transmitting and receiving optical signals. Since it is easier to use and cheaper than glass fiber, it is widely used and is particularly important in the concept of next-generation communication networks such as LAN and ISDN.

Conventionally, as shown in FIG. 5, this plastic optical fiber 01 uses PMMA (polymethylmethacrylate resin), PC (polycarbonate resin) or a copolymer resin of these for the core 02, and has a clad 0.
A step index (SI) type optical fiber having a refractive index distribution as shown in FIG.

Further, a graded index (G) having a refractive index distribution as shown in FIG. 5 (C) capable of transmitting a large amount of information per time to this SI type optical fiber.
I) type optical fiber is disclosed in, for example, Japanese Examined Patent Publication No. 52-5857,
JP-B-54-30301, JP-A-61-130904
JP-A No. 61-162008, etc., but there are various problems from the viewpoint of manufacturing, etc., and desired products have not been obtained yet.

That is, in the prior art, since the refractive index distribution is formed by utilizing the difference in reactivity and the gel effect,
In order to obtain a desired refractive index, the size of the base material, the type of material, etc. are greatly limited. Therefore, there arises a problem that mass production is difficult and a material having excellent transmission characteristics and reliability cannot be obtained. In addition, in the past, it was difficult to control the reaction freely, so an ideal GI
It was not possible to obtain a fiber having a refractive index profile of the mold with good yield.

Further, Japanese Patent Laid-Open No. 2-16504 discloses a method of concentrically extruding a laminate of two or more polymerizable mixtures having different refractive indexes, but has the following problems. . That is, since it is a laminated extrusion method, only about 10 layers of extrusion steps can be formed, and the resulting refractive index distribution has a stepwise shape, and a large amount of information cannot be sent. It is also proposed that the monomer be diffused after extrusion to have a continuous and smooth refractive index distribution, but in this case, the number of processes increases, productivity deteriorates, and further, a difficult control operation such as diffusion. Therefore, there is a problem that an ideal GI type refractive index distribution cannot be obtained.

On the other hand, the applicant of the present invention also has a plastic optical fiber plug whose refractive index continuously changes by repeatedly injecting two kinds of materials having different refractive index differences into a cylinder and polymerizing and laminating the materials under centrifugal force. Although a method for manufacturing a reform has been previously proposed (see Japanese Patent Laid-Open No. 60-119509), it takes time to manage the refractive index according to a desired design value,
There is a problem that it cannot be manufactured at a low price.

In view of the above problems, it is an object of the present invention to provide a method of manufacturing a plastic optical fiber which has a desired refractive index change and is simple and inexpensive to manufacture.

[0009]

A method of manufacturing a plastic optical fiber according to the present invention, which achieves the above object, is characterized in that a CVD (Chemical) method is applied to the inner surface of a hollow cylindrical body that rotates about an axis.
In the method for producing a plastic optical fiber preform by depositing a gas material by the vapor deposition method, a polymer A (refractive index: Na) and a compound having a different refractive index from the polymer A are used to obtain In addition to producing a low initial raw material vapor, a hollow cylindrical body having the same composition is produced, and the initial raw material vapor having the low refractive index is deposited on the inner surface of the hollow cylindrical body. The refractive index is gradually increased by changing the compounding ratio of the compound to be blended with, and a refractive index distribution is formed by gradually lowering the refractive index from the center of the optical fiber preform toward the outer diameter direction. Is characterized by.

Further, in the above-mentioned constitution, the compound containing the polymer A (refractive index: Na) as a main component and having a different refractive index from the polymer has a higher refractive index (Nb) than the refractive index (Na) of the polymer A. It is a material B which has, and is characterized by gradually increasing the compounding ratio.

In the above structure, the polymer A (refractive index: N
It is characterized in that an initial spray solution is prepared from a) and a material C having a refractive index (Nc) lower than that of the polymer A, and the compounding ratio of the material C in the spray solution is gradually decreased.

On the other hand, the construction of the first plastic optical fiber manufacturing apparatus according to the present invention is an apparatus for manufacturing a plastic optical fiber preform by depositing raw material vapor in a hollow cylindrical body by a CVD method. And a rotating device for rotatably supporting the cylindrical body of the hollow cylindrical body, which is arranged at the center of the axis of the hollow cylindrical body and is movable in the axial direction, and sprays an organic source vapor onto the inner surface of the hollow cylindrical body. A nozzle,
It is characterized by comprising a drying device for heating the organic material deposited inside the hollow cylindrical body to remove the solvent, and a raw material supply means for supplying an organic raw material vapor having a different refractive index.

The configuration of the second plastic optical fiber manufacturing apparatus is an apparatus for manufacturing a plastic optical fiber preform by depositing raw material vapor in a hollow cylindrical body by a CVD method. A rotation device that rotatably supports the shaft, a supply pipe that is arranged at one end of the hollow cylinder and that supplies the organic raw material vapor to the inner surface of the hollow cylinder, and a deposit inside the hollow cylinder. It is characterized by comprising a drying device for heating an organic material to remove a solvent and a raw material supply means for supplying an organic raw material vapor having a different refractive index.

The contents of the present invention will be described below.

FIG. 1 is a schematic view of an apparatus for producing a plastic optical fiber by the internal CVD method according to the present invention. As shown in the figure, this device includes a rotating device (not shown) for rotatably supporting the hollow cylindrical body 11 around its axis, and an axially arranged center of the hollow cylindrical body. A nozzle 12 that is reciprocally movable and has a plurality of spray holes to spray the supplied raw material vapor, and an organic raw material vapor that is axially reciprocally movable and is deposited inside a hollow cylindrical body 11 to heat the raw material. Drying device (ring heater) 13 for removing the solvent in the steam
And a supply tank 14 for supplying the organic raw material vapor and a refractive index adjustment tank 15.

Here, the raw material vapor supplied to the nozzle 12 is such that an organic raw material solution 17 is stored together with a solvent in a supply tank 14 having a heating means 16, and an inert gas (N ₂ , Ar, He, etc.) 18 Will be sent by the introduction of. Then, the refractive index is adjusted by appropriately supplying raw material solutions having different refractive indexes from the refractive index adjustment tank 15. The heating means 16 may not be provided depending on the type of organic material.

FIG. 2 shows the outline of another internal CVD method,
A supply pipe 19 for introducing the raw material vapor is directly connected to one end of the rotating hollow cylindrical pipe 11, and the nozzle 12 in FIG.
Is omitted, and the raw material vapor is directly supplied into the hollow cylindrical body 11.

Here, the polymer (hereinafter referred to as "polymer A"), which is a kind of the organic material of the present invention, means a homopolymer of methyl methacrylate (polymethyl methacrylate: PM).
MA), polycarbonate (PC), and monofunctional (meth) acrylates, fluorinated alkyl (meth) acrylates, polyfunctional (meth) acrylates, polyfunctional (meth) acrylates, acrylic acid, methacrylic acid,
A transparent copolymer of styrene, chlorostyrene, and other monomers and methyl methacrylate.

Among the above-mentioned polymers, a typical polymer A is polymethylmethacrylate (n = 1.49).
0) and polycarbonate (n = 1.59) are preferably used.

The material having a refractive index different from the refractive index (Na) of the polymer A means that the refractive index (N
a material having a higher refractive index (Nb) than a) (hereinafter,
It may be a “material B”) or a material having a low refractive index (Nc) (hereinafter referred to as “material C”), and is not limited to a monomer.

Here, as a specific example of the material when the polymer A is polymethylmethacrylate (PMMA) (Na: n = 1.49), the high refractive index material B is, for example, butylbenzyl phthalate. Ester (Nb: n
= 1.536), 2-phenylethyl acetate (n = 1.5)
1), dimethyl phthalate (n = 1.515), diphenyl sulfide (n = 1.635), vinyl benzoate (n = 1.1.5).
577), benzyl methacrylate (n = 1.568),
Examples thereof include diallyl phthalate (n = 1.518). Among the above-mentioned materials, vinyl benzoate, benzyl methacrylate and diallyl phthalate are polymerizable materials. On the other hand, examples of the material C having a low refractive index include hexyl acetate (Nb: n = 1.408) and bis (3,5,5-trimethylhexyl phthalate) (n = 1.48).
7), bis (2-methylhexyl) phthalate (n = 1.4
86) and the like.

Since the method of the present invention does not use a peculiar chemical reaction in the manufacturing process, the size of the base material to be manufactured and the kind of material can be arbitrarily selected. Therefore, it is possible to easily manufacture a base material having a size suitable for a production system by using a material having excellent characteristics, and mass-produce a desired base material. In particular, the present manufacturing method is excellent in that a non-polymerizable material having excellent transmission characteristics can be selected as a material having a refractive index different from that of the polymer A.

Next, an example of manufacturing the plastic optical fiber preform by the internal CVD method will be described with reference to FIG. The polymer A is injected into the supply tank 14 as the organic raw material solution 17 together with the solvent capable of dissolving the polymer A, and one material B is stored in the refractive index adjustment tank 15 and is accumulated every time it is deposited. In order to obtain a preset optical refractive index gradient (refractive index distribution), the material B is introduced into the supply tank 14 from the refractive index adjusting tank 15 to gradually increase the refractive index in the supply tank 14. Has changed to.

Then, as shown in FIG. 1, a hollow cylindrical body 1
While rotating 1, the nozzle 12 is reciprocally moved in the axial direction, the raw material vapor is sprayed, and the drying by the dryer 13 is performed to deposit the raw material having a gradually changing refractive index, and the outer diameter from the center of the base material is accumulated. A core layer is formed in which the refractive index gradually decreases in the direction.

After the spraying is completed, as shown in FIG. 3 (A), the base material 20 having the hollow portion 20a in the axial direction of the nozzle 12 is obtained in the central axis, so that it is heated and melted to form the collapse. Let Incidentally, FIG. 3 (B) shows a refractive index distribution chart before being collapsed.

FIG. 4A shows the plastic optical fiber preform 21 thus obtained, and FIG. 4B shows its GI type refractive index profile.

The optical fiber preform obtained as described above is subjected to a normal drawing operation, for example, holding the optical fiber preform in a vertical state and heating and melting it to obtain a desired plastic optical fiber.

Further, at least one of the polymer A and the compound B may be a photopolymerizable substance, and photopolymerization may be performed by irradiation with energy rays such as ultraviolet rays to fix a predetermined refractive index distribution. In particular, it is desirable that the initiator used for photopolymerization is one that is cleaved between different atoms by light energy. When photopolymerized in this way, there is no change with time in the refractive index distribution due to heat and the like, and it is suitable for use especially in a region where high temperature and high heat are generated. Alternatively, the hollow cylindrical body 11 may be made of an ultraviolet-transparent material, and the ultraviolet irradiation may be performed from the outside of the cylindrical body 11.

[0029]

The preferred embodiments of the present invention will be described below.

(Embodiment 1) Embodiment 1 will be described with reference to FIG. As the transparent polymer A, polymethylmethacrylate (PMMA; refractive index (Na) = 1.49
0) was used to form a hollow cylindrical body 11 containing the polymer A as a main component. In the supply tank 14, the polymer A (P
MMA) dissolved in a solvent (tetrohydrofuran: THF) at a predetermined ratio is injected. As material B, phthalic acid butylbenzyl ester having a higher refractive index than polymer A (refractive index (Nb) = 1.536) is dissolved in THF,
It was stored in the refractive index adjustment tank 15. The hollow cylindrical body 11 obtained above was placed in a rotating device (not shown), and the raw material vapor from the supply tank 14 was sprayed uniformly using the nozzle 12 in the axial direction.

At the time of this spraying, the material B is gradually supplied into the supply tank 14 from the refractive index adjusting tank 15, and the mixing ratio of the material B is increased for each spray to increase the refractive index of the spray liquid, and A plastic optical fiber preform 21 having a GI type refractive index distribution shown in FIGS. 4 (A) and 4 (B) in which the refractive index gradually decreases from the center to the outer peripheral direction is obtained.

(Second Embodiment) Similar to the first embodiment, the second embodiment will be described with reference to FIG. As the transparent polymer A, polymethylmethacrylate (PMMA; refractive index (Na) = 1.492) was used, and as the material C having a refractive index lower than the refractive index (Na) of the polymer A, hexyl acetate (refractive index) was used. Rate (Nc) = 1.408), and the two are mixed to form an initial solution.
A solution obtained by dissolving this mixed solution in a solvent (tetrohydrofuran: THF) is injected. In addition, a hollow cylindrical body (refractive index: 1.410) 11 was produced by using a mixed solution having the same composition as a main component. In the refractive index adjustment tank 15, polymer A is added to THF.
It was dissolved in and stored. The hollow cylindrical body 11 obtained above was installed in a rotating device (not shown), and the raw material from the supply tank 14 was directly supplied to the inner surface of the hollow cylindrical body 11 via the supply pipe 19 and deposited.

At the time of this deposition, the raw material A is gradually supplied from the refractive index adjusting tank 15 into the supply tank 14.
4 (A) and 4 (B), in which the blending ratio is increased for each spray to gradually increase the refractive index of the spray liquid and the refractive index gradually decreases from the center of the base material toward the outer peripheral direction. , A plastic optical fiber preform 21 having a GI type refractive index distribution was obtained.

(Evaluation of Transmission Characteristics) Each of the above-described base materials was melt-drawn and a 1 mmφ length 100 m all-plastic optical fiber (APF) was produced. 0.6 of these fibers
The results of evaluation of the transmission loss of 58 μm and the band are shown in “Table 1” below. The light source has a wavelength of 0.6 for both transmission loss and bandwidth.
Uses a 58 μm LD. In the band measurement, a pulse having a half width of 60 psec was generated in the light source, and the FFT optical oscilloscope (manufactured by Hamamatsu Photonics) was used for measurement.

[0035]

[Table 1]

[0036]

As described above with reference to the embodiments, according to the present invention, it is possible to control the refractive index distribution, which is extremely difficult by the conventional method, by an easy and simple method, and a uniform GI type plastic optical material. A fiber preform can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an internal CVD method.

FIG. 2 is a schematic view of an internal CVD method.

FIG. 3 is a distribution diagram of a base material obtained by deposition and its refractive index.

FIG. 4 is a plastic base material and its refractive index distribution chart.

FIG. 5 (A) is a schematic view of a plastic base material,
(B) is a SI type refractive index profile and (C) is a GI type refractive index profile.

[Explanation of symbols]

 11 Hollow Cylindrical Body 12 Nozzle 13 Drying Device 14 Supply Tank 15 Refractive Index Adjustment Tank

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroo Matsuda 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works

Claims (6)

[Claims] 1. A method for producing a plastic optical fiber preform by depositing a gas material on the inner surface of a hollow cylindrical body rotating about an axis by a CVD (Chemical Vapor Deposition) method, wherein a polymer A (refractive index: Na) and a compound having a refractive index different from that of the polymer A are used to prepare an initial raw material vapor having a low refractive index, and at the same time, a hollow cylindrical body having the same composition is produced to remove the initial raw material vapor having a low refractive index. It is deposited on the inner surface of the hollow cylindrical body, and every time this deposition is repeated, the compounding ratio of the compound compounded in the raw material vapor is changed to gradually increase the refractive index, and the refractive index is gradually increased from the center of the optical fiber preform. A method for producing a plastic optical fiber preform, which comprises forming a refractive index distribution in which the refractive index gradually decreases in the outer diameter direction. 2. The polymer A (refractive index:
Na) as a main component and a compound having a refractive index different from that of the polymer is the material B having a refractive index (Nb) higher than the refractive index (Na) of the polymer A, and the compounding ratio should be gradually increased. A method for manufacturing a plastic optical fiber preform characterized by the above. 3. The polymer A (refractive index:
Na) and a material C having a refractive index (Nc) lower than that of the polymer A to prepare an initial raw material vapor, and gradually reduce the compounding ratio of the material C in the raw material vapor. Base material manufacturing method. 4. An apparatus for producing a plastic optical fiber preform by depositing a raw material vapor in a hollow cylindrical body by a CVD method, and a rotating apparatus for rotatably supporting the hollow cylindrical body around its axis. A nozzle which is arranged at the center of the axis of the hollow cylinder and is movable in the axial direction, and which sprays an organic source vapor onto the inner surface of the hollow cylinder, and heats the organic material deposited inside the hollow cylinder. An apparatus for producing a plastic optical fiber preform, comprising a drying device for removing a solvent by means of a solvent and a raw material supply means for supplying an organic raw material vapor having a different refractive index. 5. An apparatus for producing a plastic optical fiber preform by depositing a raw material vapor in a hollow cylindrical body by a CVD method, and a rotating apparatus for rotatably supporting the hollow cylindrical body around its axis. A supply pipe arranged at one end of the hollow cylindrical body to supply the organic raw material vapor to the inner surface of the hollow cylindrical body, and a drying device for heating the organic material deposited inside the hollow cylindrical body to remove the solvent. And a raw material supply means for supplying organic raw material vapors having different refractive indexes, the apparatus for producing a plastic optical fiber preform. 6. The apparatus for producing a plastic optical fiber preform according to claim 4, further comprising an energy ray irradiation device for irradiating the surface of the optical fiber preform with energy rays.