JPH11160553A - Hexagonal-core plastic optical multifiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the circular plastic optical multifiber with hexagonal multicore which has small bending loss and has the transmitting quantity of light equal to that of a plastic optical fiber with a single core. SOLUTION: The plastic optical mulifiber has >=18 light-transmissive core parts of 314 to 32000 μm<2> sectional area arranged in a circularly-sectioned sea part of 0.2 to 2 mm diameter and the core parts occupy the fiber section by >=80% in terms of area and do not come into contact with the fiber outer peripheral edge and the respective core parts are hexagonal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hexagonal-core plastic multi-optical fiber used in fields such as a photoelectric sensor, a light guide, an image transmitter, and a communication.

[0002]

2. Description of the Related Art Conventionally, a multi-core plastic multi-optical fiber used for a photoelectric sensor is disclosed in
According to Japanese Patent No. 34120, the core has a diameter of 30 to 300 μm.
m is shown to be preferable.
No. 0 also discloses that the diameter of each core is preferably in the range of 5 to 50 μm.
No. 2 also discloses that the core preferably has a diameter of 50 to 200 μm.

However, in these multi-core plastic optical fibers, the loss due to bending when bent is smaller than that of a single-core plastic optical fiber.
Each light transmitting core portion is defined by a diameter, and the core portion cannot be kept circular so that the area ratio of the entire core portion cannot be 80% or more, and the total area of the light transmitting core portion is substantially reduced. Has a problem that it cannot be increased to the same size as a single-core optical fiber, and it is not possible to obtain a transmission light amount equivalent to that of a single-core plastic optical fiber.

Japanese Patent Application Laid-Open No. 1-118108 discloses a plastic multi-optical fiber having a light transmission property having a diameter of 5 to 200 μm and an island having a substantially hexagonal cross section, and the cross section of the entire optical fiber is disclosed. If the optical fiber is rectangular in shape and the cross section of the optical fiber is rectangular even if the island portion is hexagonal, bending anisotropy occurs, and it is practically impossible to use it as a photoelectric sensor.

[0005]

SUMMARY OF THE INVENTION The present inventors have conducted various studies to obtain a transmission light amount equivalent to that of a single-core plastic optical fiber with a small loss due to bending in a plastic multi-optical fiber. By making the cross-sectional shape of each core portion of the core plastic multi-optical fiber into a hexagonal shape, the total cross-sectional area of the light-transmitting core portion in the fiber cross-sectional area can be made 80% or more, and the light receiving surface can be reduced. Finding that it can be comparable to a single-core fiber,
The present invention has been reached. SUMMARY OF THE INVENTION An object of the present invention is to provide a hexagonal multi-core circular plastic multi-optical fiber having a small loss due to bending and having a transmission light amount equivalent to that of a single-core plastic optical fiber.

[0006]

According to the present invention, a diameter of 0.2 to 0.2 mm is provided.
A plastic multi-optical fiber in which 18 or more optically transmissive cores having a cross-sectional area of 314 to 32000 μm ² are arranged in a sea portion of a fiber having a substantially circular cross section of 2 mm, and a total cross section of the core in the fiber cross section. A hexagonal-core plastic multi-optical fiber characterized in that each core portion occupying 80% or more and not in contact with the outer peripheral edge of the fiber has a hexagonal shape.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The optical fiber of the present invention has a structure in which a number of cores are present in the sea area, and the cross-sectional shape of the entire fiber has a substantially circular shape having a diameter of 0.2 to 2 mm.
The core existing in the sea has optical transmission properties, and 18 or more cores having a substantially constant cross-sectional area selected from a range of 314 to 32000 μm ² are arranged in the sea. When the diameter of the cross section of the optical fiber exceeds 2 mm,
The rigidity is increased, and the compatibility in the field of use of the conventional optical fiber is lost. When the diameter is less than 0.2 mm, not only the optical transmission performance is reduced, but also it becomes difficult to form a necessary core.

In the optical fiber of the present invention, the core and the sea are formed of different resins, but another resin layer may be formed at the boundary between the core and the sea. Further, a protective layer made of another resin or the same resin as the sea portion may be provided on the outer peripheral portion of the sea portion where many core portions exist.

The optical fiber according to the present invention is characterized in that the total cross-sectional area of the core in the fiber cross section occupies 80% or more, and each core not in contact with the outer peripheral edge of the fiber has a hexagonal shape. Therefore, it is preferable to arrange the core portion in a close-packed manner in a bale-stacked shape so that the outer shape becomes close to a circle because the core portion is unlikely to be deformed. Here, the core portion in contact with the outer peripheral edge refers to a core portion in which a part of the core portion and the outer peripheral edge of the fiber directly contact without interposing another core portion as shown in FIGS. 1 and 2d. . When the core is deformed, the mode changes when the transmitted light is reflected in the optical transmission unit, causing a problem that the number of modes finally propagated is reduced.

FIGS. 1 and 2 show examples of the cross-sectional structure of the optical fiber of the present invention. 1 and 2, a is a core portion not in contact with the outer peripheral edge of the fiber, this core portion is formed of one or more types of resin, b is a sea portion, and d is a core portion in contact with the outer peripheral edge of the fiber. In FIG. 2, c is a protective layer. When the same resin as the sea part b is used for the protective layer c, it becomes the same as the sea part b in FIG.

In the optical fiber according to the present invention, the shape of the core portion in contact with the outer peripheral edge of the fiber is close to a quadrangle to a pentagon, but the total cross-sectional area of the core in the fiber cross section is set to 80% or more. In addition, the ratio of the hexagonal core portion effective for optical transmission is increased, and the optical fiber as a whole exhibits excellent optical transmission performance.

The percentage of the total cross-sectional area of the core in the fiber cross section is preferably 90% or more, and more preferably 9% or more.
5% or more and 98% or less. Incidentally, the area of the optical transmission core in a single-core optical fiber is about 96% of the fiber cross section.
It is about.

The hexagonal shape of the inner core that is not in contact with the outer peripheral edge of the fiber may be a regular hexagon, but it is preferable that the corner has a hexagonal shape having a smooth curvature. It does not matter whether each side has a straight line or a curvature.

In the optical fiber of the present invention, since the cross-sectional shape of the whole fiber is circular, bending anisotropy such as a rectangular shape does not occur. A polygonal shape may be used, and if the cross-sectional shape is a polygonal shape close to a circle, the bending anisotropy is small and it can be used in a field that does not require bending at a small curvature. Further, the optical fiber of the present invention, if the total cross-sectional area of the core in the fiber cross section is increased, the core located at the outer peripheral edge may be damaged during handling as an optical fiber, assuming its use, It is effective to provide a protective layer around the fiber.

The use of the optical fiber of the present invention is not particularly limited, and it can be used in all fields using optical fibers, such as photoelectric sensors, light guides, and image transmission bodies.
The diameter of the optical fiber, the diameter and number of cores, the material of the core, the sea, or the protective layer are determined depending on the application, and a coating layer is further provided as appropriate according to the usage of the cable or the like.

In producing the optical fiber of the present invention, a core component and a sea component are prepared, and a nozzle hole corresponding to the number of cores is arranged in a close-packed arrangement so that the outer shape becomes substantially circular. The core component and the sea component are supplied to the nozzle to form a plurality of core-sea structures, and the plurality of core-sea structures are integrated simultaneously with or after the formation of the core-sea structure, and if necessary, The optical fiber of the present invention can be manufactured by coating the protective layer with the protective layer and stretching. When a plurality of core-sea structures are integrated, the core-sea structures are brought into close contact with each other by using a base to form a hexagonal core portion so as to fill a gap. A cylindrical or funnel-shaped die is preferably used for the integration. In addition, when the core-sea structure is integrated, the core portion becomes hexagonal. However, it is possible to use a nozzle having a hexagonal cross-section in advance as a spinning nozzle, so that the hexagonal shape of the core portion can be more easily formed. .

The stretching is performed after the formation of the optical fiber or after the coating of the protective layer. The stretching ratio is determined in the range of 1.2 to 4 times so as to satisfy the required optical and mechanical properties. For the purpose of heating and cooling the optical fiber, it can be passed through a liquid in the spinning or drawing step.

When the optical fiber of the present invention is used in the form of a cable in which the outer periphery of the optical fiber is further coated with a resin, such as a photoelectric sensor or for communication, the resin is coated in a separate step or simultaneously with the production of the optical fiber. .

As the core component, various highly transparent resins used in known optical fibers are used, and various resins such as styrene, polycarbonate, methyl methacrylate and the like can be mentioned. Particularly preferred resins include a methyl methacrylate (MMA) homopolymer and a copolymer containing benzyl methacrylate (BzMA) as a main component.

As the sea component, a resin having a lower refractive index than the core component is used, and a methyl methacrylate resin,
Methyl acrylate resin, vinylidene fluoride resin,
Examples include fluorinated methacrylate-based resins, fluorinated acrylate-based resins, and Teflon-based resins.
Trifluoroethyl methacrylate homopolymer, vinylidene fluoride (2F) / tetrafluoroethylene (4
F) Copolymer, 2,2,3,3,3-pentafluoropropyl methacrylate (5FM) / 1,1,2,2-tetrahydroxyperfluorodecyl methacrylate (1
7FM) / MMA / methacrylic acid (MAA) copolymer,
5FM / 17FM / MMA / MAA copolymer, MMA /
17FM copolymer, MMA / BzMA copolymer, MMA
A blend of a polymer and a 2F / 4F copolymer is preferably used.

As the components used for the protective layer, the same resins as the core component and the sea component described above are used. Also,
Various thermoplastic resins can be used as the resin coating material. Particularly preferred resins include polyethylene, water-crosslinked polyethylene, olefin-based elastomer, chlorinated polyethylene, ethylene / vinyl acetate copolymer, blends of vinyl chloride polymer and ethylene / vinyl acetate copolymer, vinyl chloride polymer, and the like. No. Further, as a resin coating material, a thermosetting resin such as a phenol resin, a urea resin, a melamine resin, an unsaturated polyester resin, a urethane resin, an epoxy resin, a photocurable resin such as methyl methacrylate containing a photopolymerization initiator, an acrylic resin Also, poly shape memory resins such as trans isoprene, polyurethane, norbonel, and styrene / butadiene copolymer are used. Further, these resins containing fine metal powder, short metal fibers and long metal fibers are also used as resin coating materials.

In the production of the optical fiber of the present invention, the melt flow rate of each resin used for the core portion, the sea portion or the protective layer is not particularly limited, and any resin can be used as long as it is in a range where spinning is possible.

[0023]

The present invention will be described below in more detail with reference to examples.

Example 1 Polymethyl methacrylate was used as the core component, and vinylidene fluoride / tetrafluoroethylene copolymer was used as the sea component and the protective layer component.
Spinning is performed by combining a spinning nozzle in which 51 nozzle holes are arranged in a close-packed arrangement so that the outer shape is substantially circular, and a funnel-shaped die.
A plastic multi-optical fiber having a circular cross section and an outer diameter of 1.0 mm having 151 μm ² and a hexagonal light transmitting core was obtained. The ratio of the total cross-sectional area of the core to the cross-sectional area of the optical fiber was 95%. However, the shape of the core portion in contact with the outer peripheral edge of this optical fiber was square or pentagonal, and the shape of the core portion not in contact with the outer peripheral edge of the optical fiber was hexagonal.

An optical fiber cable having an outer diameter of 2.2 mm, in which a blend of a vinyl chloride polymer and an ethylene / vinyl acetate copolymer is coated on the outer periphery of the plastic multi-optical fiber, and a single-core optical fiber having an outer diameter of 1 mm An optical fiber cable (SH-4001 manufactured by Mitsubishi Rayon Co., Ltd.) having an outer diameter of 2.2 mm and coated with polyethylene is cut to a length of 2 m each, and light having a numerical aperture of NA 0.1 and a wavelength of 650 nm is incident from one end. As a result of measuring the amount of emitted light at the other end, the amount of emitted light of this plastic multi-optical fiber was almost equal to that of a single-core optical fiber. Also, this plastic multi-optical fiber has no bending anisotropy when wound once around a rod having a diameter of 2 mm, and the amount of light is 9 times before winding.
9% or more was retained.

(Comparative Example 1) The same resin as in Example 1 was used as the resin of the core component and the resin of the sea component, and spinning was performed in which 151 nozzle holes were concentrically arranged so that the outer shape was substantially circular. Spun with a nozzle, stretched by a factor of two, and with a light-transmitting core all in a circular state, a plastic with a circular cross-section with an outer diameter of 1.0 mm that maximizes the total area of the core in the cross-sectional area of the fiber A multi-optical fiber manufactured was obtained, and the ratio of the total cross-sectional area of the core to the cross-sectional area of the fiber was 78%.

This plastic multi-optical fiber and a single-core optical fiber having an outer diameter of 1.0 mm (manufactured by Mitsubishi Rayon Co., Ltd.)
SK-40) was cut to a length of 2 m, light having a numerical aperture of NA 0.1 and a wavelength of 650 nm was incident from one end, and the output light amount was measured at the other end. As a result, the output light amount of this plastic multi-optical fiber was measured. Was 83% of that of a single-core optical fiber. However, the optical fiber obtained in Comparative Example 1 had a diameter of 2 m.
There was no bending anisotropy when wound once on the rod of m, and the light amount maintained 95% or more before winding.

[0028]

The hexagonal-core plastic optical fiber of the present invention has a small loss when bent, a transmission light amount equivalent to that of a single-core plastic optical fiber, and has no bending anisotropy. , Photoelectric sensor, light guide,
It is suitably used in fields such as image transmission and communication.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of an example of a hexagonal-core plastic multi-optical fiber of the present invention.

FIG. 2 is an enlarged sectional view of another example of the hexagonal-core plastic multi-optical fiber of the present invention.

[Explanation of symbols]

 a core portion not in contact with the outer peripheral edge of fiber b sea portion c protective layer d core portion in contact with the outer peripheral edge

Claims (1)

[Claims] 1. A fiber having a substantially circular cross section having a diameter of 0.2 to ² mm and a cross section of 314 to 32000 μm ^{2 at} the sea portion.
A multi-optical fiber made of plastic having 18 or more optically transmitting cores, wherein the total cross-sectional area of the cores in the fiber cross-section occupies 80% or more and is not in contact with the outer periphery of the fiber. Is a hexagonal plastic multi-optical fiber characterized by having a hexagonal shape.