JPH11337747A - Multiple plastic optical fiber unit for communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the yield of a transceiver and to enable high-speed communication by forming the light incident side end face of a multiple plastic optical fiber so as to have a shape projecting its central part, thereby obtaining a state that the incident numerical aperture (LNA) of a light source, such as LED or LD, is made substantially low. SOLUTION: Multiple plastic optical fiber 1 is formed as fibrous composite spun yarn by enclosing and integrating >=7 pieces of core fibers consisting of a transparent core resin and the circumferences of the respective core fibers with a sheath resin having the refractive index lower than the refractive index of the core fibers. The end face 3 of the multiple plastic optical fiber 1 has the shape projecting in the central part. Light is, therefore, made incident on the end faces of the cores on the outer side at a shaper angle. Namely, the light of the lower incident NA than heretofore is eventually made incident on the end face. Since the end face of the core is more inclined toward the outer side, the light made incident on at the high NA heretofore is no more received in the peripheral part and the same state as the state when the LNA of the light source is made substantially low is obtd.

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 unit used for communication, and more particularly to an optical fiber unit having a connector terminal shape.

[0002]

2. Description of the Related Art Signal transmission means using an LED (light emitting diode) or an LD (semiconductor laser) as a light source and a multi-core plastic optical fiber as a transmission medium is known. When performing high-speed communication with a multi-core plastic optical fiber, it is necessary to reduce the numerical aperture of the multi-core plastic optical fiber. However, it is also necessary to lower the incident numerical aperture LNA of a light source such as an LED or LD. It is effective.

However, if the value of the LNA of the light source is regulated to a relatively low value, there have been problems that the amount of light is reduced and the yield of the transceiver is poor.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and realize high-speed communication using a light source such as an LED or LD and a multi-core plastic optical fiber. .

[0005]

SUMMARY OF THE INVENTION The present invention is a multi-core plastic optical fiber unit for communication in which a connector is attached to a terminal of a multi-core plastic optical fiber, wherein the multi-core plastic optical fiber is made of a transparent core resin. Seven or more core fibers, and the periphery of each core fiber is surrounded by a sheath resin having a lower refractive index than the core resin. Has a protruding shape.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies based on the fact that the transmission band of a multi-core plastic optical fiber may be affected by the coupling conditions between the light source and the multi-core plastic optical fiber. Was completed. The influence of the transmission band due to the coupling condition tends to occur when the diameter of the multi-core plastic optical fiber is larger than the size of the light source.
From this, the cause was estimated as follows. Light having a relatively small incident NA is transmitted to the center core immediately before the light source, but the incident NA is relatively large to the outer core. Usually, the size of the light source is 100 μm to 30 μm.
Since the diameter is about 0 μm and the diameter of the multi-core plastic optical fiber is about 0.5 to 1.5 mm, transmission with different incident NA is performed between the center core and the outer core. For this reason, it is considered that a time difference occurs between the signals and the band becomes narrow. Then, the present inventor has found that the problem can be solved by molding the end face of the fiber on the light source side of the multi-core plastic optical fiber connected to the light source so that the central portion protrudes. Hereinafter, embodiments of the present invention will be specifically described.

FIG. 1 schematically shows a longitudinal section of a terminal portion of an embodiment of a multi-core plastic optical fiber unit for communication according to the present invention. In the figure, 1 is a multi-core plastic optical fiber,
2 is a coating layer, 3 is an end face of the multi-core plastic optical fiber 1, and 4 is a connector.

A feature of the optical fiber unit according to the present invention is that, as shown in FIG. 1, the end face of the multi-core plastic optical fiber has a shape in which the central portion is protruded, as shown in FIG. In addition, it is preferable in terms of a manufacturing process to have a smooth curved surface protruding from the outside toward the center.

FIG. 2 is a longitudinal sectional view showing the structure of a conventional multi-core plastic optical fiber unit for communication. In FIG. 2, each member itself is common to the present invention, but conventionally, the end face of the multi-core plastic optical fiber 1 is flat.

The operation and effect of the optical fiber unit of the present invention will be described with reference to FIG. 3 (a) is an enlarged view of a central part of a multi-core plastic optical fiber of a unit of the present invention, and FIG. 3 (b) is an enlarged view of a central part of a multi-core plastic optical fiber. It is a sheath surrounding. The multi-core plastic optical fiber shown in FIG.
Is a structure in which the periphery of the core 11 is surrounded by the sheath 12 as shown in FIG.

As shown in FIG. 3, the central core 11a receives light emitted from the light source 10 to the front, so that
Light having a relatively low incident NA is incident. However, the light source of a normal LED or LD has a small light emitting portion.
Light having a higher incident NA is incident on the core 11b on the outer side of a.
Incident NA higher in the outer core away from the center core 11a
Will be incident. In the present invention, since the end face 3 of the multi-core plastic optical fiber is formed so that the center part protrudes, light is incident on the end face of the core 11b at an acute angle, that is, light having a lower incident NA than the conventional one. Will be incident. In addition, since the end face of the core is more inclined toward the outside, light that has been incident at a high incident NA in the conventional unit in the peripheral portion is no longer received in the present invention, and substantially the light source The same state as when the LNA is reduced is obtained. Therefore, when an LED or LD is used as a light source, the same effect as when the LNA of the light source itself is lowered can be obtained without lowering the LNA of the light source itself. It is possible to obtain a wide transmission band with reduction.

In the multi-core plastic optical fiber used in the present invention, the multi-core plastic optical fiber comprises seven or more core fibers made of a transparent core resin, and a sheath around each core fiber having a lower refractive index than the core resin. It is surrounded by a resin, and is collectively spun into a fibrous form. 4 and 5 schematically show the structure of one example of the multi-core plastic optical fiber used in the present invention in a cross-sectional view. 4 and 5, 1 is a multi-core plastic optical fiber, 2 is a coating layer, 11 is a core, 12, 12a, 12
b is a sheath. As a multi-core plastic optical fiber used in the present invention, as shown in FIG. 4, a core 11 is surrounded by a sheath 12 so as to be integrated, or as shown in FIG. Surrounded with each sheath 1
There is a form in which the periphery of 2a is surrounded by a second sheath 12b to be integrated, and both are manufactured by composite spinning.

In the present invention, the core resin forming the core 11 is a transparent resin having a high refractive index, and the sheath 12 or the first sheath 12a is formed of a transparent resin having a lower refractive index than the core resin. Further, in the case of the configuration of FIG. 5, the second sheath 12b is formed of a transparent resin having a lower refractive index than the first sheath 12a. In the configuration of FIG. 5, a sheath having a different refractive index may be further formed to form a sheath configuration of three or more layers. Even in this case, the sheath closest to the core has a high refractive index and is gradually stepped outward. It is formed to have a low refractive index.

As the core resin that can be used in the present invention, a resin conventionally used as a core resin for a plastic optical fiber is preferably used. Specifically, methyl resin having high transparency and suitable for long-distance transmission is used. Methacrylate resins are preferably used. In addition, a styrene resin having low hygroscopicity, a polycarbonate resin having high heat resistance and low hygroscopicity, and an amorphous polyolefin resin can be used. Further, an amorphous fluorinated polymer which can transmit light even to a near infrared light source can be used.

The sheath resin that can be used in the present invention is a transparent resin having a lower refractive index than the core resin. For example, when the core resin is a methyl methacrylate resin, a vinylidene fluoride resin is used. Is preferably used. In addition, methacrylic resins, acrylate resins, vinylidene fluoride resins, etc., such as fluoroalkyl methacrylate resins, are preferably used.

In the present invention, as the structure of the multi-core plastic optical fiber, the second sheath 1 shown in FIG.
2b can also be formed of a third resin having various functions. As the third resin, for example, a resin colored and provided with a light shielding function or a resin having a high heat resistance for use in a high temperature environment is selected according to the application.

The number of cores in the multi-core plastic optical fiber according to the present invention is 7 or more, preferably 1000
Used below zero. The average diameter of the core is 5 μm to 2
It is about 50 μm. The difference in refractive index between the core and the sheath is 0.
A range of 005 to 0.25 is possible.

As shown in FIGS. 1, 4 and 5, the multi-core plastic optical fiber according to the present invention is usually provided with a coating layer 2 further around the sheath 12 or the second sheath 12b to improve heat resistance and heat resistance. Used in the form of cables with improved mechanical properties. The coating layer 2 is formed of a known resin.

In the communication of the multi-core plastic optical fiber, a wider transmission band can be obtained by reducing the difference in the refractive index between the core and the sheath (first layer when there are many layers). The numerical aperture NA determined from the square root of the difference between the square of the refractive index of the core resin and the square of the refractive index of the sheath resin is about 0.5 to 0.1,
The band is wider as this value is smaller.

In the present invention, the shape of the end face of the multi-core plastic optical fiber may be such that the central portion protrudes.
As shown in (a), it may be formed so as to be gradually inclined outward, or it may be trapezoidal, but it is preferably a smooth curved surface such as a spherical surface for ease of processing. Desirably, the surface is mirror-finished. Such a curved surface shape can be easily processed by a method such as cutting, cutting, polishing or heating. In the present invention, the degree of protrusion of the center portion of the end face and the curvature of the curved surface are appropriately selected depending on the degree of effect to be obtained and the optical fiber used.

The effect of the present invention can be obtained with a multi-core plastic optical fiber having any NA, but is particularly effective when a wide band of 200 MHz or more is expected with a 50 m fiber length. Is 400M
Hz or more, and the effect is more significant when the frequency is 600 MHz or more. Here, the band measurement method is based on a pulse method, and is obtained by a known measurement system using an LD of 650 nm.

[0022]

EXAMPLES Example 1 1.5 g / 1 under the conditions of a refractive index of 1.492, a melt flow index of 230 ° C., a load of 3.8 kg, an orifice diameter of 2 mm and a length of 8 mm.
Using 0 minute polymethyl methacrylate resin as the core resin,
Cast polymerization of 14% by weight of 17FMA (heptadecafluorodecyl methacrylate) as a first sheath resin, 6% by weight of 4FM (tetrafluoropropyl methacrylate), 6% by weight of 3FMA (trifluoroethyl methacrylate), and 74% by weight of MMA (methyl methacrylate) A resin having a melt flow index of 25 g / 10 minutes at 230 ° C. and a load of 3.8 kg and a refractive index of 1.47 was used. NA is 0.26. As the second sheath resin, a resin of 80 mol% of vinylidene fluoride and 20 mol% of tetrafluoroethylene and having a melt flow index of 30 g / 10 min measured under the same conditions as the first sheath resin was used. The refractive index was 1.402. The composite spinning die used had 37 cores, each of which had a first sheath and a second sheath that covered two layers. The composite spinning die is supplied such that the ratio of the volume of the core resin to the volume of the first sheath resin and the volume of the second sheath resin is 80:10, and the strands discharged from the die are converged and doubled. By stretching, a two-sheath multicore plastic optical fiber bare wire having a diameter of 1.00 mm was manufactured. Further, the periphery of the bare wire was covered with black polyethylene to obtain a two-core multi-core plastic optical fiber cable having a diameter of 2.2 mm. The transmission loss of this multi-core plastic optical fiber is 650 nm wavelength, LNA 0.15
Was 140 dB / km.

This multi-core plastic optical fiber cable was taken 50 m and fixed to a PN type connector, and the end face was polished in a hemispherical shape with a polishing paper having a particle diameter of 0.2 μm so that the center of the fiber protruded from the center. . The following band measurement was performed using this multi-core plastic optical fiber unit. The measurement system was a 650 nm LD, and the pulse method was used. The LNA of the LD was fixed at 0.2. As a result, the band was 1.2 GHz.

(Comparative Example 1) The band of the same multi-core plastic optical fiber unit as in Example 1 was polished from a hemispherical shape to a planar shape, and the band was measured. As a result, the band was 900 MHz.

[0025]

As described above, according to the present invention,
Since a state in which the LNA of a light source such as an LED or an LD is substantially reduced can be obtained, the yield of the transceiver is improved and high-speed communication is realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal section schematically showing the structure of one embodiment of a multi-core plastic optical fiber unit of the present invention.

FIG. 2 is a longitudinal sectional view schematically showing the structure of an example of a conventional multi-core plastic optical fiber unit.

FIG. 3 is a diagram showing the operation of the present invention.

FIG. 4 is a cross-sectional view schematically showing the structure of an example of a multi-core plastic optical fiber used in the present invention.

FIG. 5 is a cross-sectional view schematically showing the structure of another example of the multi-core plastic optical fiber used in the present invention.

[Explanation of symbols]

 Reference Signs List 1 multi-core plastic optical fiber 2 coating layer 3 end face 4 connector 10 light source 11, 11a, 11b core 12, 12a, 12b sheath

Claims (5)

[Claims] 1. A multi-core plastic optical fiber unit for communication comprising a connector attached to a terminal of a multi-core plastic optical fiber.
Seven or more core fibers made of a transparent core resin, and each core fiber is surrounded by a sheath resin having a refractive index lower than that of the core resin, and is collectively spun into a fibrous composite light, and light is incident. A multicore plastic optical fiber unit for communication, wherein a side end surface has a shape in which a central portion protrudes. 2. The multicore plastic optical fiber unit for communication according to claim 1, wherein the light incident end surface has a curved surface that protrudes smoothly from the outside toward the center. 3. The multi-core plastic optical fiber surrounds each core fiber with a first sheath resin to form a first sheath, and further surrounds each first sheath with a first sheath resin. 3. The multicore plastic optical fiber unit for communication according to claim 1 or 2, wherein the optical fiber unit is surrounded by a second sheath resin having a low refractive index. 4. The multi-core plastic optical fiber is formed by surrounding each core fiber with a sheath resin to form a sheath, and further surrounding each sheath with a third resin to form the sheath. Or the multi-core plastic optical fiber unit for communication according to 2. 5. The multi-core plastic optical fiber according to claim 5, wherein
The multicore plastic optical fiber unit for communication according to any one of claims 1 to 4, wherein a transmission band having a length of 0 m is 200 MHz or more.