JPH09101424A - Optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber which prevents a light signal from leaking when a bent part is present in a transmission path for light. SOLUTION: A light passage bending area 5 is formed at the part where the travel direction of the light signal of the optical fiber 1 is bent. The light passage bending area 5 includes a high-order mode fiber part 5a which is made less in diameter than the principal body part 1a of the optical fiber 1 and tapered propagation mode conversion area 5b which is gradually increased in diameter gradually on both the sides of the high-order mode fiber part 5a and has its maximum diameter equal to that of the principal body 1a. The outer periphery of the high-order mode fiber part 5a and both the propagation mode conversion parts 5b is coated with a reinforcing clad layer with a low refractive index.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber used in an optical communication such as an indoor optical communication network when a bent portion is provided in the middle of a transmission path in a space inside a wall or a side surface of a device.

[0002]

2. Description of the Related Art As an indoor optical communication network, for example, as disclosed in Japanese Patent Laid-Open No. 63-257704, an optical signal is transmitted via an optical fiber wired between a central device and terminals in a building. There is a method of exchanging data.

In this system, the optical fiber is wired by utilizing the space inside the wall of the building, the space under the floor, etc., and the optical outlet is installed at a necessary portion such as the wall surface or the floor surface as the lead-out portion of the optical fiber. However, an optical plug from a central device or a terminal is detachably connected to the optical outlet.

[0004]

However, it is necessary to bend the optical fiber appropriately when wiring the optical fiber using the space inside the wall of the building, the space under the floor, or the like. Since the space in the partition has a narrow width, the bending radius of the optical fiber becomes small, which causes a problem due to leakage of an optical signal due to the bending.

In particular, an optical fiber for broadband optical communication has a small numerical aperture, and even if the transmission path is slightly bent, leakage of an optical signal is remarkable.

Therefore, an object of the present invention is to provide an optical fiber which prevents leakage of an optical signal when there is a bent portion in the optical transmission path.

[0007]

The technical means for solving the above problems is an optical fiber having an optical path bending region for bending the traveling direction of an optical signal in the middle of a transmission path in optical communication. The bending region is a high-order mode fiber portion having a smaller diameter than the diameter of the main body portion of the optical fiber, and the diameter is gradually increased on both sides of the high-order mode fiber portion, and the maximum diameter thereof is the main body portion. It is provided with a tapered propagation mode conversion region portion having the same diameter.

Further, the outer periphery of the high-order mode fiber portion and both propagation mode conversion regions may be coated with a clad layer having a low refractive index.

Further, the optical fiber may have a structure in which a plurality of the optical path bending regions are provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
Reference numeral 1 denotes an optical fiber for optical communication, which is a GI plastic optical fiber, for example, a so-called low numerical aperture optical fiber having a small numerical aperture such as product names "Esca Giga" and "Esca Mega" manufactured by Mitsubishi Rayon Co., Ltd.

An optical path bending region 5 for bending the traveling direction of the optical signal is provided at the end of the optical fiber 1 located in the space 3 in the wall 2.

The optical path bending region 5 has a central high-order mode fiber portion 5a in which the optical fiber 1 itself is heated and drawn to have a diameter smaller than that of the main body portions 1a on both sides, and the high-order mode fiber portion 5a. On both sides of the portion 5a, a tapered propagation mode conversion region portion 5b having a gradually increasing diameter and a maximum diameter equal to that of the main body portion 1a is provided. Both propagation mode conversion areas 5b are formed symmetrically with each other.

Further, as shown in FIG. 3, the optical fiber 1 comprises a central core 7 and a clad 8 provided around the core 7 and having a refractive index slightly smaller than the refractive index of the core 7. Further, in the present embodiment, the higher-order mode fiber section 5a and each propagation mode conversion area section 5b.
A reinforcing clad layer 9 coated with a polymer having a refractive index smaller than that of the clad 8 such as a resin having a low refractive index is provided over the outer circumference of the.

A connection connector 11 made of ABS, PBT, or the like is connected to the main body 1a at the end of the optical fiber 1. The connection connector 11 is mounted on the wall mounting frame 12, and the wall mounting frame 12 is attached to the wall. It is attached to the wall of 2 and constitutes a so-called optical outlet.

The optical fiber 1 inserted into the space 3 in the wall 2 is wired in the higher mode fiber portion 5a of the optical path bending region 5 with the transmission path bent upward. .

A connection connector (not shown) which is connectable to the connection connector 11 mounted on the end of the other optical fiber 15 from the device side is connected to the connection connector 11 on the wall mounting frame 12 side. Here, the end face of the main body 1a of the optical fiber 1 and the end face of the optical fiber 15 are optically coupled.

At this time, the optical fiber 1 wired in the wall 2
It is desirable that the refractive index of the core 7 and the refractive index of the core of the optical fiber 15 on the device side are the same.

The first embodiment of the present invention is configured as described above, and the optical signal incident from the optical fiber 15 side is guided to the main body 1a of the optical fiber 1 and propagates in the subsequent optical path bending region 5. When reflected at the mode conversion region 5b, the propagation mode (angle θ1 of the traveling direction of light with respect to the optical axis L of the optical fiber 1) is forcibly converted to a higher-order propagation mode. That is, the angle θ1 in the traveling direction of light with respect to the optical axis L of the optical fiber 1 is converted to a larger angle θ2.

Then, in this higher-order propagation mode,
When passing through the bent high-order mode fiber portion 5a and being reflected by the other propagation mode conversion area portion 5b subsequent thereto, the higher-order propagation mode is forcibly reconverted to the lower-order propagation mode. It That is, the angle θ2 in the traveling direction of light with respect to the optical axis L of the optical fiber 1 is reconverted to the original small angle θ1.

Thereafter, the optical signal returned to the low-order propagation mode is transmitted through the main body 1a in the optical fiber 1.

By the way, FIG. 4 shows the wavelength of light λp = 653n.
Numerical aperture NA = 0.5 using m laser diode as light source
Shows a relational data diagram between the bending radius and the light transmission rate of the plastic optical fiber with the numerical aperture NA = 0.25 and the optical transmission rate, and the plastic optical fiber with the numerical aperture NA = 0.5 corresponds to the bending. It can be seen that there is little light leakage. From this fact, the higher-order propagation mode causes less light leakage to bending than the lower-order propagation mode, and the higher-order propagation mode can also reduce the minimum bending radius effective for optical signal transmission.

Therefore, in the case of the present embodiment, since the propagation mode of the optical signal is bent by the high-order mode fiber portion 5a which is transmitted by converting the propagation mode of the optical signal into the higher-order propagation mode, Since the leakage of the optical signal can be effectively prevented and the minimum bending radius r can be made smaller, the high-order mode fiber section 5a can be made very short, and the lowering of the optical signal band in the middle of the transmission path can be effectively prevented. The low loss and wide band can be maintained, and the transmission performance can be improved.

Further, since the reinforcing clad layer 9 is provided on the outer periphery of the high-order mode fiber portion 5a and each propagation mode conversion area portion 5b, the leakage of the optical signal can be prevented more effectively, and the attachment and shape of dust can be prevented. Can be prevented and the optical stability can be improved.

FIG. 5 shows a second embodiment, in which the wall 2
The optical fiber 1 is wired by utilizing the space portion 3 inside and the space portion 18 inside the ceiling 17. And the light path bending region 5
Is provided at the bent position of the back side position portion of the wall mounting frame 12 which is the optical outlet position and the intersection of the wall 2 inner space portion 3 and the ceiling 17 inner space portion 18 respectively.

As described above, when the optical fiber 1 is wired, by providing the optical path bending region 5 in each of the bent portions, it is possible to effectively prevent the band reduction of the optical signal in the middle of the transmission path, and to perform a good transmission. Performance can be secured.

In the above embodiment, the structure in which the reinforcing clad layer 9 is provided on the outer periphery of the high-order mode fiber portion 5a and the propagation mode conversion area 5b is shown, but the structure does not have the reinforcing clad layer 9. May be. Further, the structure without the clad 6 may be adopted.

Further, the inclination angle θ and the length S in the optical axis direction of the propagation mode conversion area 5b may be appropriately determined according to the band of the optical signal used.

Further, a structure is shown in which the optical path bending region 5 of the optical fiber 1 is arranged in a portion in the wall 2 or the ceiling 17 where it is wired in a bent shape. The number of the optical path bending regions 5 is not limited to the number in the embodiment, as long as it is arranged in a portion where the traveling direction of the optical signal is bent in a narrow space. Furthermore, the connector 1
The shape and structure of No. 1 may be appropriately determined according to the purpose, and are not limited to the shape and structure of the embodiment.

The reinforcing clad layer 9 may have a structure in which an optical adhesive is applied, for example, DEFEN manufactured by Dainippon Ink and Chemicals, Inc. having a refractive index of 1.479.
There are SA and OP-48.

[0030]

As described above, according to the optical fiber of the present invention, the optical path bending region is provided in the middle of the transmission path, and the optical path bending region has a diameter smaller than the diameter of the main portion of the optical fiber. A high-order mode fiber portion and a taper-shaped propagation mode conversion area portion whose maximum diameter is gradually increased on both sides of the high-order mode fiber portion and whose maximum diameter is the same as that of the main body portion. The optical signal propagation mode is converted into a higher-order propagation mode and transmitted by the higher-order mode fiber section that bends the traveling direction of the optical signal, so that the leakage of the optical signal is effective. Since it can be prevented and the minimum bending radius can be made smaller, the high-order mode fiber can also be made very short, and it is possible to effectively prevent lowering of the optical signal band in the middle of the transmission path, maintaining low loss and wide band. You can There is an advantage that can be improved in performance.

If the outer periphery of the high-order mode fiber portion and both propagation mode conversion area portions is coated with a clad layer having a low refractive index, leakage of optical signals can be prevented more effectively, and There is an advantage that it is possible to prevent the adhesion of dust and the influence on the change of the shape, and to improve the optical stability.

Further, by providing each of the optical path bending regions at the desired position of the optical fiber, there is an advantage that the band reduction of the optical signal in the middle of the transmission path can be effectively prevented and good transmission performance can be secured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part of a first embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is an explanatory view of a main part of the optical fiber.

FIG. 4 is a relational data diagram between a bending radius of a plastic optical fiber and a light transmission rate.

FIG. 5 is a schematic diagram of a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 1a Main part 5 Optical path bending region 5a Higher-order mode fiber part 5b Propagation mode conversion part 7 Core 8 Cladding 9 Reinforcement cladding layer

Claims (3)

[Claims] 1. An optical fiber having an optical path bending region for bending a traveling direction of an optical signal in a transmission path in optical communication, wherein the optical path bending region has a diameter smaller than a diameter of a main portion of the optical fiber. A high-order mode fiber portion, and a tapered propagation mode conversion region portion having a diameter gradually increasing on both sides of the high-order mode fiber portion and having a maximum diameter equal to that of the main body portion. An optical fiber characterized by 2. The optical fiber according to claim 1, wherein outer peripheries of the high-order mode fiber portion and both propagation mode conversion regions are coated with a clad layer having a low refractive index. 3. The optical fiber according to claim 1, wherein a plurality of the optical path bending regions are provided.