JP2000266967A - Signal transmitting method of multicore hollow fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compactly realize many channels of optical fiber in a small space made of plastics optical fiber by inserting a positioning pin provided on the element side in the hollow part of fiber, holding the diameter of a hollow part to be constant, and simultaneously with it positioning the center of the fiber. SOLUTION: A multicore hollow fiber having a hollow part on the center part is used, and a plurality of signal channels are formed. In this case, it is constituted of light emitting elements 11, a positioning pin 12, a multicore hollow fiber 10, a hollow part 2 formed on the center part, and territories corresponding to the diameter of the light emitting elements 11, namely signal channels 3. In the connecting part of at least one side of light emitting elements 11 and the light receiving elements and the fiber 10, the positioning pin 12 provided on the element 11 side is inserted in the hollow part 2 of the fiber 10, and simultaneously with holding the diameter of the hollow part 2 constant, the center of the fiber 10 is aligned. In this case, it is necessary for wiring corresponding to twist of the multicore hollow fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal transmission method using a multi-core hollow fiber.

[0002]

2. Description of the Related Art As a method for realizing a large number of optical channels in a small space, several tens of quartz optical fibers, 12
Fiber tapes arranged at a pitch of 5 μm are used, and a large number of terminal connections can be made together. Similar tapes are available for plastic optical fibers, but their dimensional accuracy is poor due to expansion and contraction and the like, and practical use has been difficult.

When trying to realize a large number of optical fiber channels in a small space in a small space using plastic optical fibers, one idea is that the diameter of the optical fiber is 100 μm.
It is conceivable that a very thin plastic optical fiber of about m to 260 μm is arranged in a sheet form as a tape and a signal is sent to each fiber. However, it is very difficult to perform terminal processing for overcoming the dimensional accuracy of the plastic optical fiber.

When a multi-core plastic optical fiber having several to thousands of fine cores neatly contained in a diameter of about 1.0 mm is used, a plurality of signal transmission paths are formed by one fiber. I can do it.

However, even in this case, the variation of the diameter of the plastic optical fiber obtained by spinning is ± 3%.
Degree occurs. If a 1.0 mm plastic optical fiber is used, a variation of 970 μm to 1030 μm occurs,
Further, when the fiber is mounted on the ferrule of the connector, the inner diameter of the ferrule varies from about 1060 μm to 1100 μm. The alignment of the fiber becomes very difficult.

[0006]

The problem to be solved by the present invention is to solve the above-mentioned problems and to realize a large number of optical fiber channels in a small space made of plastic optical fiber in a compact manner.

[0007]

SUMMARY OF THE INVENTION The present invention is a hollow fiber structure having at least one hollow portion parallel to the core inside, and adjacent to a plurality of cores made of a transparent core resin having a high refractive index. A multi-core hollow fiber signal transmission method comprising simultaneously melting and molding a sheath layer made of a transparent sheath resin having a lower refractive index than the core resin surrounding each core so as to fill the gap between the cores. At the joint between at least one of the elements and the fiber, a positioning pin provided on the element side is inserted into the hollow part of the fiber, and the center of the fiber is aligned while the diameter of the hollow part is kept constant. It is characterized by the following.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the present invention resides in the use of a multi-core hollow fiber. The multi-core hollow fiber itself is disclosed in U.S. Pat. No. 5,471,553 and JP-A-6-18.
It is disclosed in JP-A-6445 and is well known. The multi-core hollow fibers described in these prior arts are:
Mainly used as light guides, endoscopes and optical sensors used in the medical and measurement fields.

As described in the above-mentioned document, the structure of the multi-core hollow fiber is one in which one or more hollow portions parallel to the core are arranged in a multi-core plastic optical fiber. The present inventor uses this hollow portion for positioning of the multi-core hollow fiber, and as a result, it has become possible to easily perform high-precision positioning which cannot be performed by the conventional cylindrical connector ferrule.

[0010] For example, the simplest structure of a multi-core hollow fiber is a doughnut-shaped cross section and one hollow portion at the center of the fiber, and the tip portion is slightly smaller than the diameter of the hollow portion. By arranging the positioning pin 12 having a slightly thicker root portion and inserting the multi-core hollow fiber into the positioning pin 12, the fiber can be supported and the eccentricity of the fiber can be prevented at the same time. FIG. 1 shows a cross-sectional structure of such a fiber. In the figure, reference numeral 1 denotes a core, which is schematically shown by fine squares. The sheath layer is arranged to fill between adjacent cores. Also, 2
Is a hollow portion, and 3 is a region corresponding to the diameter of the light receiving element or the light emitting element.

FIG. 7 shows a normal cross section of a multi-core hollow fiber in an embodiment to be described later. FIG. 8 is a cross-sectional view when a circular positioning pin is mounted in the hollow portion 2. Comparing these figures, it can be seen that in the case of FIG. 7, the cross section of the hollow portion 2 is a slightly crushed circle, but in FIG. 8, it is a perfect circle. By processing both ends of the multi-core hollow fiber in this manner, the arrangement and shape of the cores at the end faces at both ends can be left and right or overlap each other.

This is achieved by making the inside diameters of both ends the same, especially when the multi-core hollow fiber is produced only by the composite spinning disclosed in US Pat. No. 5,471,553.

FIGS. 2 to 5 show examples of the structure of another multi-core hollow fiber, and the symbols in the figures are the same as those in FIG.

FIG. 6 shows an embodiment of the present invention in which a multi-core hollow fiber having a hollow portion in the center is used.
FIG. 7 is a conceptual diagram of a terminal unit when a plurality of (six in FIG. 6) signal channels are formed. In the figure, reference numeral 11 denotes a light emitting element, 12 denotes a positioning pin, 10 denotes a multi-core hollow fiber, 2 denotes a hollow portion formed in the center thereof, and 3 denotes a region corresponding to the diameter of the light emitting element 11, that is, a signal channel. The core of the fiber is schematically shown by a square in the cross section of the fiber. In the present invention, it is necessary to perform the arrangement corresponding to the twist of the multi-core hollow fiber, and if this point is satisfied, the terminals can be accurately coupled to each other. If this twisting process is complicated,
As the multi-core hollow fiber, a fiber provided with one or more hollow portions in addition to the positioning hollow portion may be used, or a mark may be provided on the outside of the fiber.

The microstructure of the multi-core hollow fiber used in the present invention comprises a plurality of cores made of a transparent core resin and a transparent sheath having a lower refractive index than the core resin surrounding each core so as to fill the gap between the cores. A single sheath layer made of a resin, and a first sheath layer made of a transparent first sheath resin having a lower refractive index than the core resin provided around each of the cores, and further provided concentrically with the core; It is basically the case that the first sheath layer is surrounded by a second sheath layer made of a second sheath resin having a lower refractive index. In the latter case, the first sheath layer defines the numerical aperture of the fiber and the second sheath layer is used to contribute to improving light loss due to bending. Also, this second
Instead of the sheath layer, a protective layer or a light-shielding layer may be provided, which is not necessarily transparent and is not necessarily related to the refractive index. The light shielding layer is covered with a resin containing carbon black or the like. Providing this layer is advantageous when forming a high-density transmission line because light crosstalk between cores can be prevented. The number of cores of the multi-core hollow fiber is 7 or more to form a circumference, and preferably 20 to 5000. The larger the number of cores, the smaller the diameter of the core. Usually, the diameter of this core is 10 μm or more.

Since the diameter of the light receiving / emitting element or the like connected at the end of the multi-core hollow fiber is usually 50 to 200 μm, it is necessary to consider the size of this coupling element as the diameter of the core so that the connection can be performed well. Good. Therefore, the diameter of the core is from 10 μm to 30 μm
What is necessary is just to select suitably the thing of 100 micrometers-100 micrometers, and the big thing of 100 micrometers-200 micrometers.

The outer diameter of the multi-core hollow fiber is usually 0.5 to 3.0 mm. The diameter of the hollow portion of the multi-core hollow fiber is about 1% to 90% of the outer diameter. In particular, it is advantageous to reduce the diameter of the hollow portion because buckling when the fiber is bent hardly occurs.
When the diameter of the hollow portion is large and there is a fear of buckling, buckling can be prevented by inserting an appropriate fiber into the hollow portion.

As the core resin of the multi-core hollow fiber used in the present invention, a resin known as a core resin of a conventional plastic optical fiber can be used. For example, a known resin based on polymethyl methacrylate (MMA) can be used. For example, methyl methacrylate homopolymer or a copolymer containing 50% by weight or more of methyl methacrylate, and copolymerizable components such as acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, and ethyl methacrylate Methacrylates such as propyl methacrylate and cyclohexyl methacrylate, maleimides such as isopropylmaleimide, acrylic acid, methacrylic acid, and styrene. . As other preferable resins, styrene resins can be used. For example, a styrene homopolymer or a styrene-methyl methacrylate copolymer is used. As other preferable resins, polycarbonate resins can be used. Polycarbonate resins have high heat resistance and low hygroscopicity. CYT made by Asahi Glass Co., Ltd., which is also proposed as a core resin for plastic optical fibers
OP resin, DuPont TEFLONAF resin, JSR
Arton resin manufactured by the company can also be used as the core resin.

Specific examples of the sheath resin include a resin containing a fluoroalkyl methacrylate, a vinylidene fluoride resin, or a mixture of a vinylidene fluoride resin and a methacrylate resin when the core resin is an MMA resin. Alloys. In particular, for communication applications, fluoroalkyl methacrylate resins are preferred because they have no crystallinity and do not change loss at high temperatures. The fluoroalkyl methacrylate is a compound represented by the following formula, and is a copolymer of at least one kind of the fluoroalkyl methacrylate monomer represented by these with another copolymerizable fluoroalkyl methacrylate, alkyl methacrylate, or alkyl acrylate.

[0020]

Embedded image

More specifically, examples of the fluoroalkyl methacrylate include trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, pentafluoropropyl methacrylate, heptadecafluorodecyl methacrylate, and octafluoropropentyl methacrylate. Acrylate monomers include trifluoroethyl acrylate, tetrafluoropropyl acrylate, octafluoropentyl acrylate, and the like. In addition to these fluorine-based monomers, various combinations with methacrylate monomers such as methyl methacrylate and ethyl methacrylate, acrylate monomers such as methyl acrylate, ethyl acrylate, and butyl acrylate, and methacrylic acid and acrylic acid as high refractive index components And copolymers of the following.

Examples of the vinylidene fluoride resin include a copolymer of vinylidene fluoride and hexafluoroacetone, or a tertiary or higher copolymer obtained by adding trifluoroethylene or tetrafluoroethylene to these binary components. Polymers, furthermore, copolymers of vinylidene fluoride and hexafluoropropene, or ternary or higher copolymers obtained by adding trifluoroethylene or tetrafluoroethylene to these binary components, and furthermore, vinylidene fluoride and tetrafluoroethylene Binary copolymer of fluoroethylene, in particular, 80 mol% of vinylidene fluoride and tetrafluoroethylene 20
Copolymers consisting of mol% are preferred. Other examples include a binary copolymer of vinylidene fluoride and trifluoroethylene. Further, alloys obtained by mixing these vinylidene fluoride resins and methacrylate resins can also be used.

[0023]

EXAMPLE The core resin was polymethyl methacrylate (PMM).
A) A resin, wherein the sheath resin is a copolymer of vinylidene fluoride and tetrafluoroethylene having a refractive index of 1.403, an outer diameter of 1.0 mm, and a hollow portion provided at the center having a diameter of 0.6 mm. A multicore hollow fiber having a core diameter of 30 μm and a core number of 500 was used. FIG. 7 is a cross-sectional view when the end face of the multi-core hollow fiber is cut with a razor. This multi-core hollow fiber has a diameter of 0.61 mm
FIG. 8 is a cross-sectional view of the end face into which the positioning pins are inserted. 7 and 8 are drawings drawn based on micrographs.

As shown in FIGS. 7 and 8, the diameter of the hollow portion 2 of the multi-core hollow fiber was 1.06 in FIG. 7, while the ratio of the long diameter to the single diameter was 1.06. In FIG. 8, the value is corrected to 1.01 which is close to a perfect circle. It was found that even if the same cross-sectioned photographs of the fiber were superimposed on the cross section of the fiber 5 m downstream from the end face, they coincided with high accuracy of 15 μm or less.

[0025]

As described above, according to the present invention, the positioning pin is inserted into the hollow portion of the multi-core hollow fiber and coupled with the coupling element, so that complicated terminal processing is not required and high-precision positioning can be easily performed. It is possible to realize multi-channel signal transmission in a narrow space using a plastic optical fiber.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a multi-core hollow fiber used in the present invention.

FIG. 2 is a schematic cross-sectional view of another example of the multi-core hollow fiber used in the present invention.

FIG. 3 is a schematic cross-sectional view of another example of the multi-core hollow fiber used in the present invention.

FIG. 4 is a schematic cross-sectional view of another example of the multi-core hollow fiber used in the present invention.

FIG. 5 is a schematic cross-sectional view of another example of the multi-core hollow fiber used in the present invention.

FIG. 6 is a conceptual diagram of a terminal when a plurality of signal channels are formed in a multi-core hollow fiber according to an embodiment of the present invention.

FIG. 7 is a sectional view of a multi-core hollow fiber used in an example of the present invention.

FIG. 8 is a cross-sectional view of an end face of a multi-core hollow fiber in which a positioning pin is inserted into a hollow portion in the embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 core 2 hollow part 3 area equivalent to diameter of light emitting element or light receiving element (signal channel) 10 multi-core hollow fiber 11 light emitting element 12 positioning pin

Claims (2)

[Claims] At least one hollow portion parallel to the core is provided inside.
It is a hollow fiber structure having a plurality of cores made of a transparent core resin having a high refractive index and a transparent sheath resin having a lower refractive index than the core resin surrounding each core so as to fill a space between adjacent cores. A method for transmitting a signal of a multi-core hollow fiber obtained by simultaneously melt-molding a sheath layer and a multi-core hollow fiber, wherein a positioning pin provided on the element side is provided at a coupling portion between at least one of a light emitting element and a light receiving element and the fiber. A signal transmission method for a multi-core hollow fiber, wherein the signal is inserted into a hollow portion and the center of the fiber is aligned while the diameter of the hollow portion is kept constant. 2. The method according to claim 1, wherein the number of cores of the multi-core hollow fiber is seven or more.