JPH0713028A - 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 high 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 surface of a supporting rod rotating around its axis by a CVD (Chemical Vapor Deposition) method. This initial raw material vapor is deposited on the surface of the supporting rod 11 via a nozzle 12 and the compounding ratio of the compd. to be compounded in the raw material vapor is changed at every repetition of this deposition, by which the refractive index is successively lowered. The refractive index distribution in which the refractive index is successively lowered from the center to the outside diametral direction of 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. 3, in the plastic optical fiber 01, PMMA (polymethylmethacrylate resin), PC (polycarbonate resin) or a copolymer resin of these is used for the core 02, and the cladding 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. 3 (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 Vapou) is formed on the surface of a support rod rotating about an axis.
In the method for producing a plastic optical fiber preform by depositing a gaseous material by the r.
(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 high refractive index,
The high-refractive-index initial raw material vapor is deposited on the surface of the supporting rod, and each time this deposition is repeated, the compounding ratio of the compound to be blended in the raw material vapor is changed, and the refractive index is gradually lowered. It is characterized in that 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.

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 lower refractive index (Nb) than the refractive index (Na) of the polymer A. It is a material B having a composition, and is characterized by gradually decreasing the compounding ratio.

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

On the other hand, the structure of the 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 on the surface of the supporting bar by the CVD method. A rotating device that rotatably supports the shaft, a nozzle that is reciprocally movable in the axial direction and sprays organic material vapor onto the surface of the supporting rod, a drying device that heats the deposited organic material to remove the solvent, and a refraction device. A raw material supply means for supplying organic raw material vapors having different rates.

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 external CVD method according to the present invention. As shown in the figure, this device is provided in a reaction tank 10 and is reciprocally movable in the axial direction with a rotation device (not shown) that rotatably supports a support rod 11 around its axis. A nozzle 12 for spraying the generated raw material vapor, and a drying device (a ring heater) that heats the organic raw material vapor deposited inside the support rod 11 so as to be axially reciprocally movable together with the nozzle 12 to remove the solvent in the raw material vapor. ) 13, a supply tank 14 for supplying the organic material vapor to the nozzle 12, and a refractive index adjusting 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 is supplied. 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.

Here, a 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 polymethacrylate (n = 1.49).
0) and polycarbonate (n = 1.59) are preferably used.

Further, the material having a refractive index different from the refractive index (Na) of the polymer A means the refractive index (N
a material having a lower refractive index (Nb) than a) (hereinafter,
It may be a “material B”) or a material having a high 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 material B having a low refractive index is, for example, hexyl acetate (Nb). : N = 1.408), bis (3,5,5-trimethylhexyl) phthalate (n = 1.
487), bis (2-methylhexyl) phthalate (n =
1.486) etc. can be illustrated. On the other hand, examples of the material C having a high refractive index include butyl benzyl phthalate (Nb: n = 1.536), 2-phenylethyl acetate (n = 1.51), and dimethyl phthalate (n = 1.36). 51
5), diphenyl sulfide (n = 1.635), vinyl benzoate (n = 1.577), benzyl methacrylate (n = 1.568), diallyl phthalate (n = 1.518)
Etc. can be illustrated. Among the above-mentioned materials, vinyl benzoate, benzyl methacrylate and diallyl phthalate are polymerizable materials.

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 producing the plastic optical fiber preform by the external 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, while rotating the support rod 11, the nozzle 12 is reciprocated in the axial direction, the raw material vapor is sprayed, and the drying by the dryer 13 is performed to gradually change the refractive index. The raw material is deposited to form a plastic optical fiber preform 19 in which the refractive index gradually decreases from the center of the preform toward the outer diameter direction.

FIG. 2A shows the plastic optical fiber preform 19 thus obtained, and FIG. 2B shows its GI type refractive index profile.

The optical fiber preform obtained as described above is subjected to a normal drawing operation, for example, the optical fiber preform is held in a vertical state and heated and melted to obtain a desired plastic optical fiber.

Further, at least one of the polymer A and the compound B may be a photopolymerization substance, and photopolymerization may be carried out 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 supporting rod 11 may be made of a material that is transparent to ultraviolet rays, and the irradiation of ultraviolet rays may be performed from the outside of the cylindrical body 11.

[0026]

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 the support rod 11 using the polymer A as a main component. In the supply tank 14, polymer A (PMM
A solution of A) dissolved in a solvent (tetrohydrofuran: THF) at a predetermined ratio is injected. As the material B, hexyl acetate having a lower refractive index than the polymer A (refractive index (Nb) =
1.408) was dissolved in THF and stored in the refractive index adjustment tank 15. The supporting rod 11 obtained above is installed in a rotating device (not shown), and the raw material vapor from the supply tank 14 is supplied to the nozzle 1.
2 was used to spray uniformly over 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 at each deposition to lower the refractive index of the raw material solution, and A plastic optical fiber preform 19 having a GI type refractive index distribution shown in FIGS. 2A and 2B, in which the refractive index gradually decreases from the center toward the outer peripheral direction, was obtained.

(Second Embodiment) Similar to the first embodiment, the second embodiment will be described with reference to FIG. Polymethylmethacrylate (PMMA; refractive index (Na) = 1.490) was used as the transparent polymer A, and butylbenzyl phthalate was used as the material C having a refractive index higher than the refractive index (Na) of the polymer A. Ester (refractive index (Nc) = 1.53
6) was used to mix the two to prepare an initial solution, and the mixed solution (refractive index: 1.507) was prepared in the supply tank 14.
Is dissolved in a solvent (tetrohydrofuran: THF) and injected. Further, a supporting rod (refractive index: 1.507) 11 was produced by using a mixed liquid having the same composition as a main component. Polymer A was dissolved in THF and stored in the refractive index adjustment tank 15. The obtained supporting rod 11 was installed in a rotating device (not shown), and the raw material from the supply tank 14 was deposited on the outer surface of the supporting rod 11 through the nozzle 12.

At the time of this deposition, the raw material A is gradually supplied into the supply tank 14 from the refractive index adjusting tank 15 to obtain the raw material A.
2 (A) and 2 (B), the mixing ratio of is increased for each deposition to gradually decrease the refractive index of the raw material solution, and the refractive index gradually decreases from the center of the base material toward the outer peripheral direction. , A plastic optical fiber preform 19 having a GI type refractive index distribution was obtained.

(Evaluation of Transmission Characteristics) Each of the above-mentioned base materials was melt-drawn and a 1 mmφ 100 m long 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.

[0032]

[Table 1]

[0033]

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 external CVD method.

FIG. 2 is a plastic base material and its refractive index distribution chart.

FIG. 3A 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 Support Rod 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 (5)

[Claims] 1. The surface of a support rod rotating about an axis is provided with C
In a method for producing a plastic optical fiber preform by depositing a gas material by a VD (Chemical Vapor Deposition) method, a polymer A (refractive index: Na) and a compound having a different refractive index from the polymer A are used. An initial raw material vapor having a high refractive index is produced, and the initial raw material vapor having a high refractive index is deposited on the surface of the supporting rod. Each time the deposition is repeated, the compounding ratio of the compound to be blended in the raw material vapor is set. Of the plastic optical fiber preform characterized by forming the refractive index distribution by gradually changing the refractive index and gradually decreasing the refractive index from the center of the optical fiber preform toward the outer diameter direction. Production method. 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) lower than the refractive index (Na) of the polymer A, and the blending ratio is gradually decreased. 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) higher 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 on the surface of a supporting rod by a CVD method, the rotating apparatus supporting the supporting rod rotatably around its axis, and an axial direction. A nozzle that is reciprocally movable to spray the organic raw material vapor on the surface of the support rod, a drying device that heats the deposited organic material to remove the solvent, and a raw material supply means that supplies the organic raw material vapor having a different refractive index. An apparatus for manufacturing a plastic optical fiber preform, comprising: 5. 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.