JP2002031727A - Optical fiber cable and end face processing method thereof - Google Patents

Abstract

(57) Abstract: The present invention relates to an optical fiber cable suitable for use in an optical communication system for transmitting an optical signal through a common single-core optical fiber cable of a full-duplex optical communication system, and an optical fiber cable therefor. It is an object to provide an end face processing method. SOLUTION: An end surface of a core portion serving as a light transmission path of an optical fiber cable is an end surface 401 for scattering reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable suitable for use in an optical communication system for transmitting an optical signal via a single optical fiber cable common to full-duplex optical communication systems. .

[0002]

2. Description of the Related Art A prior art 1 relating to one-way communication using an optical fiber cable is shown in FIG. In order for the optical transceiver 1401 and the optical transceiver 1402 to transmit information via the optical fiber cable 1407, for example, when transmitting an optical signal from the optical transceiver 1401 to the transceiver 1402, as shown in FIG. One end of the optical fiber cable 1407 is connected to the transmission unit 1 of the optical transceiver 1401.
403 can be realized by connecting the other end of the optical fiber cable 1407 to the receiving unit 1404 of the optical transceiver 1402.

When transmitting an optical signal from the optical transceiver 1402 to the optical transceiver 1401, one end of the optical fiber cable 1407 is connected to the optical transceiver 1 as shown in FIG.
An optical fiber cable 140 is connected to a receiving unit 1405 of 401.
7 can be realized by connecting the other end to the receiving unit 1406 of the optical transceiver 1402.

At this time, when it is desired to always transmit an optical signal from the optical transceiver 1401 to the optical transceiver 1402, the receiving unit 1
The transmission unit 1403 and the reception unit 1404 are not necessary when the optical transmission / reception unit 1402 does not need the transmission unit 405 and the transmission unit 1406.

Here, if it is desired to transmit an optical signal from the optical transceiver 1401 to the optical transceiver 1401 at the same time as transmitting an optical signal from the optical transceiver 1401 to the optical transceiver 1402, FIG. As shown, another optical fiber cable 1408 is prepared, and the transmitting unit 1403 is provided.
The receiving unit 1405 and the transmitting unit 1406 must be connected by the remaining optical fiber cable 1408 while the and the receiving unit 1404 are connected by the optical fiber cable 1407.

That is, in the prior art 1, the optical transceiver 14 is used.
01 and the optical transceiver 1402 want to perform full-duplex communication with each other, two optical fiber cables must be prepared.

[0007] As can be seen in the prior art 1, when transmitting and receiving an optical signal, the optical signal transmitted through the optical fiber cable travels only in one direction, and full-duplex communication is performed by one optical fiber cable. No optical fiber cable was suitable for performing full-duplex communication with a single cable.

Therefore, in order to perform full-duplex communication using a single optical fiber cable, a new technique for that purpose is required.

Further, as a prior art 2, there is one in which the end face of an optical fiber cable is formed on a convex lens surface to improve the transmission efficiency by utilizing the light-collecting ability. In addition,
As a method of processing the end surface of the optical fiber cable having the end surface of the convex lens surface, as described in JP-A-5-2111, an end surface of a plastic optical cable is formed into a concave shape of a concave lens formed on a heating plate. There is a technology in which the end surface of an optical cable is processed into a convex lens surface by pressing the optical cable.

Japanese Patent Publication No. Sho 57-57001 discloses a third prior art in which the tip of a plastic optical fiber is formed into a tapered shape (a truncated cone) to prevent the optical fiber from coming off. It has been disclosed.
According to this, it is possible to prevent the position of the end face of the optical fiber from being shifted due to the pulling of the optical fiber, and the optical fiber from coming off from the cylindrical body (plug portion).

Japanese Patent Application Laid-Open No. 1-101103 discloses a prior art 4 in which a dish-shaped concave portion is provided at the end of a connector, and an optical fiber core material is flowed into the concave portion to form the optical fiber core. No. 6,086,045. Further, it describes that the end face of the core material and the end face of the connector are made the same surface, and that the amount of protrusion of the end face of the core material is constant. According to the prior art 4, the distance between the end face of the plastic optical fiber cable and the light receiving element is appropriately maintained, so that the transmission efficiency of transmission and reception can be stably increased.

[0012]

However, as described in the above-mentioned prior art 1, there has been no one suitable for performing full-duplex communication using a single optical fiber cable. .

That is, in the conventional optical fiber cable, it is not assumed to be applied to the dual optical communication, and the end face has a flat surface.
Note that FIG. 15 will be referred to for the following description.
FIG. 1A is a conceptual diagram when full-duplex communication is attempted between optical transceivers 1501 and 1502 using a conventional optical fiber cable 1503, and FIG.
(B) is a partial enlarged view near the distal end of the optical fiber cable 1503.

First, when full-duplex optical communication is performed using a common single-core optical fiber cable 1503, an optical signal transmitted from the optical transceiver 1501 is transmitted to the inner surface 1505 of one end of the optical fiber cable 1503. Reflected light (far-end reflection), and reflected light that returns to the other end surface 1504 of the optical fiber cable 1503 is generated. Then
By such reflected light, a communication partner (optical transceiver 15
02) may be erroneously recognized as an optical signal transmitted from (2).

Second, the optical fiber cable 1503 is
An optical fiber cable 1503 is inserted into and removed from the insertion hole of the connector of each of the optical transceivers 1501 and 1502.
A mechanism is required to prevent the end face of the optical fiber cable 1503 from being displaced when the cable is pulled.
Therefore, when the above-described prior art 3 is adopted, an optical signal from the transmission unit of the optical transceiver 1501 is transmitted to the optical fiber cable 1.
503 is reflected (near-end reflection) by a tapered (frustoconical) inclined portion near the end surface 1504 of the optical transceiver 150.
No. 1 is input to the receiving unit. When such reflected light is input to the receiving unit, a problem such as erroneous recognition as an optical signal transmitted from a communication partner occurs.

Further, even if the end face of the optical fiber cable is made to have a convex lens surface just to have a light condensing function as in the above-mentioned prior art 2, similarly, the near-end reflection of the optical fiber cable as described above, Due to the far-end reflection, a problem such as erroneous recognition as an optical signal transmitted from a communication partner occurs.

Further, in the above-mentioned prior arts 3 and 4,
Neither the near-end reflection nor the far-end reflection of the optical fiber cable is taken into account, and when applied to a full-duplex optical communication system, a problem such as erroneous recognition as an optical signal transmitted from a communication partner occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is an optical communication system for transmitting an optical signal through a common single-core optical fiber cable of a full-duplex optical communication system. It is an object of the present invention to provide an optical fiber cable suitable for use in an optical fiber and a method for processing an end face thereof.

[0019]

In order to solve the above problems, an optical fiber cable according to the present invention is characterized in that a core portion serving as a light transmission path is provided with an end face for scattering reflected light. In order to make the end face that scatters the reflected light, for example, the end face may be made rough, and preferably the end face has a roughness of 1 μm.
m to 10 μm.

According to the present invention, by providing the end face for scattering the reflected light, when the light inside the optical fiber cable is emitted from the end face, the light is reflected by the inner face of the end face (far-end reflection). The reflected light is diffused. Here, the light passing through the optical fiber cable is transmitted more efficiently as the light is parallel to the central axis of the optical fiber cable, and the transmission efficiency becomes worse as the direction is shifted from the central axis of the optical fiber cable. There is a nature. Therefore, the transmitted signal light is reflected (far-end reflection) on the inner surface of one end face of the optical fiber cable, and the reflected light returning to the other end face of the optical fiber cable is scattered and greatly attenuated. Reflected light can be reduced.

Further, in the ordinary optical transmission / reception device, since it is designed to pick up a large amount of light parallel to the central axis of the optical fiber cable, the reflected light generated by being reflected (far end reflection) on the inner surface of the end surface of the optical fiber cable. However, the light is scattered and rebounds at an angle deviating from the central axis of the optical fiber cable, so that such scattered reflected light is hardly picked up.

As a result, a common single-core optical fiber cable of the full-duplex optical communication system can be provided without causing the problem that the reflected light is mixed with the optical signal transmitted from the communication partner and becomes noise. It is possible to realize an optical fiber cable suitable for use in an optical communication system that transmits an optical signal via the optical fiber cable.

In the optical fiber cable according to the present invention, the end face of the core serving as a light transmission path has a convex surface, and the radius of curvature of the convex surface is 0.8 d when the diameter of the core is d. From 1.8d to 1.8d.

According to the present invention, the end face is not made a convex lens surface so as to simply have a light collecting function, but the end face has a radius of curvature of 0.8d to 1.8d (where d is the diameter of the core portion).
When the light inside the optical fiber cable is emitted from the end face, the reflection direction of the reflected light generated by being reflected (far end reflection) on the inner face of the end face depends on the central axis of the optical fiber cable. And the direction deviates greatly.

Therefore, the transmitted signal light is reflected (far-end reflection) on the inner surface of one end face of the optical fiber cable, and the reflected light returning to the other end face of the optical fiber cable can be greatly reduced. Optical communication that transmits optical signals through a common single-core optical fiber cable of full-duplex optical communication system without causing problems such as mixing of reflected light into optical signals transmitted from a communication partner and becoming noise. An optical fiber cable suitable for use in a system can be realized.

The optical fiber cable according to the present invention is characterized in that the end face of the core serving as a light transmission path is concave. The radius of curvature of the concave surface of the end face is preferably from 0.5d to 3.0d, where d is the diameter of the core.

According to the present invention, by making the end face concave, when light inside the optical fiber cable is emitted from the end face, reflected light generated by being reflected (far end reflection) on the inner face of the end face is generated. The direction of reflection is largely deviated from the central axis of the optical fiber cable.

Therefore, the transmitted signal light is reflected (far-end reflection) on the inner surface of one end face of the optical fiber cable, and the amount of reflected light returning to the other end face of the optical fiber cable can be greatly reduced. The optical signal is transmitted through a common single-core optical fiber cable of the full-duplex optical communication system without such a problem that such reflected light is mixed with the optical signal transmitted from the communication partner and becomes a noise. An optical fiber cable suitable for use in an optical communication system can be realized.

Further, in the optical fiber cable of the present invention, a truncated conical shape in which a core portion serving as a light transmission path spreads toward an end face is formed at a distal end portion, and the inclined portion of the truncated conical shape and the horizontal portion of the core portion are formed. The angle formed by the portion is 30 ° or less or 60 ° or more.

According to the present invention, the core portion expands toward the end surface at the tip end portion, and the angle between the core portion and the horizontal portion forms 30 ° or less or 60 ° or more, and the inclined portion has a truncated cone shape. As a result, the signal light from the transmission unit of the optical transceiver is reflected (near-end reflection) by the inclined portion having the truncated cone shape at the end face of the optical fiber cable, and the reflected light is input to the reception unit of the optical transceiver. Can be greatly reduced, and such a problem that such reflected light mixes with an optical signal transmitted from a communication partner and becomes noise can be prevented.

Therefore, it is possible to realize an optical fiber cable suitable for use in an optical communication system for transmitting an optical signal via a single optical fiber cable common to full-duplex optical communication systems.

Further, the optical fiber cable according to the present invention is characterized in that an inclined portion is formed at the distal end where the core portion serving as a light transmission path narrows toward the end surface.
In order to form such an inclined portion, at least the tip of the core serving as a light transmission path is covered with a covering member, and the tip of the covering member is at an acute angle with respect to the central axis,
This can be easily realized by covering the tip of the covering member with the core. In addition, at least the distal end of the core serving as the light transmission path is covered with the covering member, and the inner wall of the hole into which the core of the covering member is inserted has an inclined portion that narrows toward the distal end. May be processed.

According to the present invention, a signal light from the transmitting part of the optical transceiver is formed by forming a slanted part in which the core part serving as the light transmission path narrows toward the end face at the tip part. The reflected light which enters from the end face of the optical fiber cable and is reflected (near-end reflected) on the surface of the covering member and which is input to the receiving section of the optical transceiver can be greatly reduced. It is possible to prevent problems such as mixing with the optical signal transmitted from the device and causing noise.

Therefore, it is possible to realize an optical fiber cable suitable for use in an optical communication system for transmitting an optical signal through a common single-core optical fiber cable of the full-duplex optical communication system.

Further, the optical fiber cable of the present invention is used in a full-duplex optical communication system in which one end of the core serving as a light transmission path has a convex surface, and one core of the core transmits and receives bidirectional light. It is characterized by the following.

According to the present invention, since the end face of the core serving as a light transmission path is a convex surface and is used in a full-duplex optical communication system in which bidirectional light is transmitted and received by one core consisting of the core, the present invention is applied. According to the above, the end face is not made to be a convex lens surface so as to simply have a light condensing function, but the end face is made to be a convex surface having a radius of curvature of 0.8d to 1.8d (where d is the diameter of the end surface). When the light inside the optical fiber cable is emitted from the end face, the reflection direction of the reflected light generated by being reflected (far end reflection) on the inner face of the end face is largely deviated from the central axis of the optical fiber cable.

Therefore, it is possible to greatly reduce the reflected light which is transmitted (far end reflection) on the inner surface of one end face of the optical fiber cable and returns to the other end face of the optical fiber cable. Optical communication that transmits optical signals through a common single-core optical fiber cable of full-duplex optical communication system without causing problems such as mixing of reflected light into optical signals transmitted from a communication partner and becoming noise. An optical fiber cable suitable for use in a system can be realized.

Further, the optical fiber cable of the present invention is used in a full-duplex optical communication system in which a core end surface serving as a light transmission path has a convex surface, and bidirectional light transmission / reception is performed with a single core comprising the core. It is characterized by the following.

According to the present invention, by using a full-duplex optical communication system in which the end face of a core serving as a light transmission path is a convex surface and one core of the core transmits and receives bidirectional light. When the light inside the fiber cable is emitted from the end face,
The direction of reflection of the reflected light generated by reflection (far-end reflection) on the inner surface of the end surface is largely deviated from the central axis of the optical fiber cable, and the transmitted signal light is reflected on the inner surface of one end surface of the optical fiber cable. Reflected light that is (far-end reflected) and returns to the other end face of the optical fiber cable can be greatly reduced, and such reflected light mixes with an optical signal transmitted from a communication partner to cause a problem such as noise. Will not be.

When the above-described optical fiber cable of the present invention is variously combined, it is used for an optical communication system for transmitting an optical signal through a common single-core optical fiber cable of a full-duplex optical communication system. However, a more suitable optical fiber cable can be realized.

In the method for processing an end face of an optical fiber cable according to the present invention, in the method for processing an end face of an optical fiber cable in which at least a periphery of a core portion made of a plastic material is covered with a covering member, an inner wall surface is formed at the tip portion. Using a truncated cone-shaped covering member that spreads toward the distal end,
The core is heated and deformed with the tip of the core protruding from the covering member, and the end of the core is processed into a truncated conical shape that spreads toward the end face.

Further, according to the method for processing an end face of an optical fiber cable of the present invention, in the method for processing an end face of an optical fiber cable in which at least a periphery of a core portion made of a plastic material is covered with a covering member, the front end portion has a center axis. A coating member having an acute angle is used, and the core is heated and deformed in a state where the tip of the core protrudes from the coating member, and the end face is processed so that the core covers the tip of the coating member. Things.

In the method for processing an end face of an optical fiber cable according to the present invention, a heating plate is used to heat the core, and the shape formed on the heating plate is transferred to the core.
You may make it process the end surface of a core part into a convex surface, a concave surface, or a rough surface.

According to the present invention, the end processing of the optical fiber cable as described above can be easily performed, and the optical signal is transmitted through the common single-core optical fiber cable of the full-duplex communication system. An optical fiber cable suitable for use in an optical communication system can be realized.

[0045]

Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1] As Embodiment 1, first,
The basic configuration of an optical communication system that transmits an optical signal via a common single-core optical fiber cable such as a full-duplex communication system to which the present invention can be applied will be described with reference to FIG. .

As shown in FIG. 1A, in this optical communication system, an optical transceiver 101 and an optical transceiver 105 communicate with each other via a common single-core optical fiber cable 109 in a full-duplex communication system. It transmits optical signals. Then, the connector 102 of the optical transceiver 101 and the optical transceiver 105
Optical fiber cable 1
A plug portion which is a tip portion of the connector 09 is inserted and optically connected.

Also, as shown in FIG. 1B, these connectors 102 and 106 are respectively composed of transmitting sections 103 and 107 having light emitting elements for emitting optical signals, and receiving sections having light receiving elements for receiving optical signals. The front ends 110 and 111 of the optical fiber cable 109 are inserted into the connectors 102 and 106, respectively.

Here, while transmitting an optical signal from the optical transceiver 101 to the optical transceiver 105 via the optical fiber cable 109, the same optical signal is transmitted from the optical transceiver 105 to the optical transceiver 101. An example is given in the case where the data is transmitted at the same time. That is, this is a case where full-duplex communication using optical signals is performed using a single-core optical fiber cable.

Transmission of an optical signal from the optical transceiver 101 to the optical transceiver 105 can be realized by the transmission unit 103 irradiating the distal end 110 of the optical fiber cable 109 with the optical signal. Further, transmission of an optical signal from the optical transceiver 105 to the optical transceiver 101 can be realized by irradiating an optical signal to the distal end portion 111 of the optical fiber cable 109 with the optical signal.

At this time, the receiving unit 10 of the optical transceiver 101
4 mainly receives an optical signal from the optical transceiver 105,
At the same time, some optical signals are emitted from the transmitting section 103 of the optical transceiver 101 and returned by near-end reflection near the end face of the tip section 110 or far-end reflection on the inner surface of the end face of the tip section 111.

Therefore, the present invention provides such a tip 1
Optical signals due to near-end reflection near the 10 end face and far-end reflection on the inner face of the end face 111 are sufficiently reduced to enable full-duplex communication.

[Second Embodiment] As a second embodiment, the end face of the core portion serving as the light transmission path of the optical fiber cable is made convex,
A description will be given of an optical fiber cable in which an optical signal is reduced by far-end reflection.

First, the principle will be described with reference to FIG. 2 which is a conceptual diagram conceptually showing light ray reflection by far-end reflection.

In a conventional optical fiber cable, FIG.
As shown in (A), the light ray is reflected by the far end reflection on the inner surface of the optical fiber cable core end face 201, but its reflection angle does not deviate much from the central axis of the optical fiber cable. This causes a problem such as incorrect recognition as an optical signal transmitted from a communication partner.

On the other hand, if the core end face 202 of the optical fiber cable is made convex as shown in FIG. 2B, the angle of the light reflected by the far-end reflection greatly deviates from the central axis of the optical fiber cable. Such a defect can be prevented.

Next, the result of the study on the curvature of the convex surface of the end face of the optical fiber cable core will be described with reference to FIG.

FIG. 3 shows an optical fiber cable having a length of 1 m and a diameter of 1 mm (diameter of a core portion). The end portion of the core portion is formed as a convex lens, and the optical fiber cable is measured at different curvatures. FIG. 3 shows the measurement results of the reflection efficiency of the first embodiment and the calculation results by an optical simulation simulating the tip.

The calculation of the far-end reflectivity in FIG. 3 will be described with reference to FIG. 1. When the transmitting section 103 of the optical transceiver 101 is illuminated, the value is calculated as follows. A is the amount of light detected by the receiving unit 104 of the optical device 101, and the amount of light is detected by the receiving unit 104 of the optical transceiver 101 by immersing in the same oil as the refractive index of the optical fiber cable so as to eliminate reflection from the tip. Is represented by B, and (the amount of light detected by the receiving unit 108 of the optical transceiver 105) is represented by C, the expression is expressed by (AB) / C.

As shown in FIG. 3, the measured and calculated values are close to each other. By making the end face of the optical fiber cable convex, the reflection at the far end face of the optical fiber cable is reduced from the flat state. You can see that.

FIG. 3 shows that the far-end reflectance is particularly low when the radius of curvature of the convex surface is from 0.8 mm to 1.8 mm.

From this, the radius of curvature of the convex surface of the end face of the optical fiber cable is given by:
It is understood that when the distance is set from 0.8d to 1.8d, return light due to far-end reflection can be sufficiently reduced.

[Third Embodiment] In a third embodiment, an end surface of a core portion serving as a light transmission path of an optical fiber cable is used as an end surface for scattering reflected light, and an optical signal is reduced by far-end reflection of the optical fiber cable. Things will be described.

First, the principle will be described with reference to FIG. 4, which is a conceptual diagram conceptually showing light ray reflection by far-end reflection.

In this embodiment, as shown in FIG. 4, the end face 401 for scattering the reflected light is used as the core end face of the optical fiber cable. The component in which the reflection angle largely deviates from the central axis of the fiber cable increases, and the return light due to the far-end reflection can be sufficiently reduced.

Next, as such a scattering end surface, a case where the end surface of the optical fiber cable core portion is roughened will be examined, and the result will be described with reference to FIG.

FIG. 5 shows, as an example, a length of 1 m and a diameter of 1 m.
m (core diameter) optical fiber cable, the core end surface of which is formed into a convex lens shape having a radius of about 1.6 mm, and the optical fiber cable is made to have a smooth core end surface as usual. The reflectance of the far end face of the optical fiber cable is compared with a state in which the tip of the cable core is polished with a polishing paper made of an abrasive having a particle size of 3 μm or 10 μm and roughened (similar to Embodiment 2 above). It is a figure which shows the result of having measured.

Here, for example, the particle size (diameter) is 3 μm
The grain size of the abrasive used for the roughening is defined as roughness so that the roughness of the core end by polishing the abrasive paper made of the above abrasive is 3 μm.

From FIG. 5, in any case, the reflectance from the far end of the optical fiber cable is lower at the roughened end face than at the smooth end face.

Further, as a result of examining the roughness of the end face, it was found that the difference from the smooth end face was 1 μm or more and 10 μm or less, at which the shape of the tip of the optical fiber cable core did not deform. It has been confirmed that if there is any problem, return light due to far-end reflection can be sufficiently reduced without any trouble.

[Embodiment 4] As Embodiment 4, a description will be given of an optical fiber cable in which an end surface of a core portion serving as a light transmission path of an optical fiber cable has a concave surface and an optical signal is reduced by far-end reflection of the optical fiber cable. .

First, the principle will be described with reference to FIG. 6, which is a conceptual diagram conceptually showing light ray reflection by far-end reflection.

In the present embodiment, as shown in FIG. 6, by forming the core end surface 601 of the optical fiber cable as a concave surface, the light beam of the reflected light due to the far-end reflection is greatly shifted from the central axis of the optical fiber cable. That is, return light due to far-end reflection can be sufficiently reduced.

Next, the result of study on the curvature of the convex surface of the end face of the optical fiber cable core will be described with reference to FIG.

FIG. 7 shows an optical fiber cable having a length of 1 m and a diameter of 1 mm (diameter of a core portion) when the end face of the core portion is formed as a concave lens and the curvature of the concave lens is changed.
It shows a calculation result by an optical simulation simulating the tip. The method of calculating the far-end reflectance is the same as in the second and third embodiments. In FIG. 7, (A) shows that the radius of curvature of the concave surface is from 0.6 mm to 3.
0B shows data of 0 mm, and (B) shows data of 0.6 mm to 100 mm.
mm, and POF is an abbreviation for plastic optical fiber.

FIG. 7 shows that the far-end reflectance is particularly low when the radius of curvature of the concave surface is from 0.6 mm to 3.0 mm.

It should be noted that under the above conditions, the radius of curvature of the concave surface is equal to 0.
When the diameter is 5 mm, a concave surface is formed by a hemispherical spherical surface, and when the diameter is smaller than 5 mm, the spherical surface forming the concave surface protrudes from the core of the optical fiber cable. Therefore, the result of the above simulation is 0.6
mm or more. Considering the actual concave processing of the core end face, the radius of curvature is possible if it is 0.5 mm or more, but is preferably 0.6 mm or more.

From this, the radius of curvature of the concave surface of the end face of the optical fiber cable is given by:
It is understood that when the distance is set from 0.5d to 3.0d, return light due to far-end reflection can be sufficiently reduced. Further, in consideration of actual concave surface processing, the lower limit is preferably set to 0.6d.

In this embodiment, as in the third embodiment, the same effect as in the third embodiment can be obtained even if the end face is made to scatter reflected light, that is, even if the end face is made rough.

[Fifth Embodiment] As a fifth embodiment, a truncated conical shape in which a core portion serving as a light transmission path spreads toward an end face at the tip end of an optical fiber cable, and the inclined portion having the truncated conical shape and the core are formed. A description will be given of the case where the angle between the horizontal portion and the horizontal portion is 30 ° or less or 60 ° or more to reduce the optical signal due to the near-end reflection of the optical fiber cable.

First, the principle will be described with reference to FIG. 8, which is a conceptual diagram conceptually showing light ray reflection due to near-end reflection.

FIG. 8 shows a conventional optical fiber cable.
As shown in FIG.
At the tip, the angle between the truncated cone-shaped inclined portion of the core portion and the horizontal portion of the core portion is not considered, and the optical signal from the transmitting section 802 is reflected by the truncated cone-shaped inclined portion and received. The incident light enters the unit 801 and such a reflected light mixes with an optical signal transmitted from a communication partner to cause a problem such as noise.

On the other hand, in the present embodiment, FIG.
As shown in FIG. 8 (B), the angle between the frusto-conical inclined portion of the core portion and the horizontal portion of the core portion is 60 ° or more (70 ° to 90 ° in the illustrated example). ), The angle between the inclined portion having the truncated cone shape of the core portion and the horizontal portion of the core portion is set to 30 ° or less, so that the optical signal from the transmitting section 802 can transmit the inclined portion having the truncated cone shape. Thus, even if the light is reflected by the light source, the light is not incident on the receiving unit 801, so that a problem due to near-end reflection can be prevented. The angle formed by the truncated cone-shaped inclined portion of the core and the horizontal portion of the core can also be expressed as the angle formed by the truncated cone of the core and the central axis of the core.

Next, the result of study on the angle of the truncated cone shape of the core at the end of the optical fiber cable will be described with reference to FIG.

FIG. 9 shows an optical fiber cable having a horizontal portion having a core diameter of 1 mm (diameter of a core portion). The end face of the optical fiber cable has a convex lens shape, and the radius of curvature r (mm) of the convex lens.
To r = 0.8, 0.85, 0.9, 1.0, 1.6,
The figure shows the calculation results of the relationship between the inclination angle of the truncated cone shape of the core and the near-end reflectance of the optical fiber cable when 2.0 and ∞ are changed. In addition, the truncated cone shape of the core portion extends from the horizontal portion diameter of the core portion of 1 mm in the direction of the end face, spreads 0.25 mm on both sides at the end face, and has a diameter of 1.5 mm.

FIG. 10 schematically shows a calculation method based on optical simulation assuming that there is no reflection from the far end of the optical fiber. That is,
As shown in FIG. 10, an optical fiber cable 1001 including a slope portion 1002 having a truncated cone shape at a convex end surface 1003.
And a transmitting unit 1006 and a receiving unit 1007, a lens 1004 for restricting light from the transmitting unit 1006 and a lens 1005 for restricting reflected light from the optical fiber cable 1001 are arranged. A partition plate 1008 is provided to prevent direct light from entering.

FIG. 9 shows that if the inclination angle of the truncated conical shape of the core is 30 ° or less or 60 ° or more, the near-end reflection of the optical fiber cable is obtained regardless of the radius of curvature of the convex end face. It can be understood that the optical signal due to the above can be greatly reduced.

It is to be noted that this embodiment may be combined with any of Embodiments 2 to 4 described above, so that not only the near-end reflection of the optical fiber cable but also the optical signal due to the far-end reflection is reduced. A suitable optical fiber cable can be realized by the full-duplex system.

[Embodiment 6] In Embodiment 6, the method for processing the end face of the optical fiber cable of Embodiment 5 will be described.
This will be described with reference to FIG.

As shown in FIG. 11A, in the optical fiber cable according to the present embodiment, a main portion of a core portion 1104 made of a plastic material is covered with a covering portion 1103, and the periphery of the distal end portion is covered with a plug portion 1105. Have been. The distal end portion of the plug portion 1105 is counterbored, and the inner wall surface 1108 has a truncated cone shape extending toward the distal end. Note that a metal material such as stainless steel or brass can be used for the plug portion 1105.

As shown in FIG. 11A, the core 1104
Are approximately the same diameter up to the distal end, and the distal end 1106 projects from the distal end of the plug 1105. Then, as shown in FIG.
The sheet 106 is brought into contact with the heated heating plate 1102 by pressing it, and is heated and deformed. This allows
As shown in FIG. 11C, an inclined portion 110 corresponding to the shape of the inner wall surface of the plug portion 1105 is provided at the tip of the core portion 1104.
9 can be formed.

Further, in the present embodiment, the heating plate 1102
The surface in contact with the core portion 1104 is formed in a concave shape, whereby a convex surface 1107 can be formed on the end surface of the core portion 1104. That is, the shape formed on the heating plate 1102 is transferred to the end face of the core portion 1104, and the end face is simultaneously shaped.

FIG. 11D is a sectional view of a main part of the tip portion of the optical fiber cable. In order to make the end face of the core portion 1104 concave, the heating plate 1102 may have a convex shape. Also, a rough surface shape can be formed on the heating plate 1102, and the rough surface shape can be transferred to make the end surface of the core portion 1104 rough. It is possible.

As described above, the optical fiber cables according to the second to fourth embodiments can be easily realized by processing the end faces.

[Seventh Embodiment] As a seventh embodiment, an optical fiber cable has a structure in which a tip portion of an optical fiber cable has an inclined portion in which a core serving as a light transmission path narrows toward an end face. A description will now be given of a case in which the optical signal is reduced by the near-end reflection.

First, the principle will be described with reference to FIG. 12 which is a conceptual diagram conceptually showing light ray reflection due to near-end reflection.

In consideration of FIG. 8 used in the description of the fifth embodiment, if the inclination angle of the truncated cone is set to 90 ° or more, the core portion becomes narrower toward the end face as shown in FIG. The structure is such that an inclined portion is formed. At this time, the distal end of the optical fiber cable core portion does not have a truncated cone shape, but does not have the shape shown in FIG. 8C, and the optical signal reflected from the inclined portion 1204 from the transmitting portion 1202 is received by the receiving portion 120.
1 is not incident. Therefore, if such a configuration can be realized, a problem due to near-end reflection can be prevented, and the present embodiment is for realizing such a configuration.

That is, in the present embodiment, FIG.
(C) As shown in FIG.
The tip of the plug 1305 covering the tip of the plug 4 is at an acute angle with respect to the center axis thereof.
By adopting a structure in which the end of the core 1304 covers the end of the optical fiber cable 5, the optical signal due to the near-end reflection of the optical fiber cable is reduced as shown in FIG.

The method for processing the end face according to the present embodiment will be described with reference to FIG.

As shown in FIG. 13 (A), the optical fiber cable before processing has a core 1 made of a plastic material.
A main portion of the plug 304 is covered with a covering portion 1303, and a periphery of the tip portion is covered with a plug portion 1305. The plug portion 1305 has an acute angle at the tip with respect to the central axis, and a metal material such as stainless steel or brass can be used as the material.

As shown in FIG. 13A, the core 1304
Are approximately the same diameter up to the distal end, and the distal end 1306 protrudes from the distal end of the plug portion 1305. Then, as shown in FIG.
The 306 is brought into contact with the heated heating plate 1302 by being pressed against the heated heating plate 1302, and is heated and deformed. This allows
As shown in FIG. 13C, the tip of the plug 1305 at an acute angle with respect to the central axis is covered by the tip of the core 1304, and the inclined portion 1309 at which the core 1304 narrows toward the end face is formed. The structure can be formed.

Further, in the present embodiment, in the sixth embodiment,
Similarly to the above, the surface of the heating plate 1302 that comes into contact with the core 1304 has a concave shape, whereby a convex surface 1307 can be formed on the end surface of the core 1304. That is, the shape formed on the heating plate 1302 is transferred to the end face of the core portion 1304, and the end face is simultaneously shaped.

In order to make the end face of the core 1304 concave, the heating plate 1302 may be formed with a convex shape. In addition, a rough surface shape can be formed on the heating plate 1302, and the rough surface shape can be transferred to make the end surface of the core portion 1304 rough. It is possible.

As described above, the optical fiber cable of the present embodiment can be easily realized by processing the end face.

In order to form a structure in which an inclined portion in which a core portion serving as a light transmission path narrows toward the end face is formed at the distal end portion of the optical fiber cable, as shown in FIG. Optical fiber cable core portion 130 of portion 1305
On the inner wall surface of the hole where 4 is inserted,
This is also possible by forming an inclined portion 1309 'that narrows toward the distal end.

According to the embodiment described above,
Similarly to the above-described related art 3 and the fifth and sixth embodiments, it is possible to prevent the position of the end face of the optical fiber from being shifted due to the pulling of the optical fiber and the optical fiber from coming off from the plug portion.

Note that this embodiment may be combined with any of Embodiments 2 to 7 described above, so that not only near-end reflection of the optical fiber cable but also optical signals due to far-end reflection are reduced. A suitable optical fiber cable can be realized by the full-duplex system. One example is
In a configuration in which the tip of the plug covering the tip of the optical fiber cable core is at an acute angle with respect to the central axis, and the tip of the plug is covered with the core, the optical fiber cable end face (core end face) is rough and convex. Can be cited.

[0108]

As described above, according to the optical fiber cable of the present invention, by reducing the reflected light due to the near-end reflection and the far-end reflection, a common single-core optical fiber cable of the full-duplex optical communication system is provided. It is possible to realize an optical fiber cable suitable for use in an optical communication system that transmits an optical signal via the optical fiber cable.

According to the method for processing an end face of an optical fiber cable of the present invention, such an optical fiber can be easily realized by processing the end face.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing a basic configuration of an optical communication system for transmitting an optical signal via a common single-core optical fiber cable such as a full-duplex communication system to which the present invention can be applied.

FIG. 2 is a diagram conceptually illustrating light ray reflection due to far-end reflection according to a second embodiment.

FIG. 3 is a diagram illustrating a measurement result of a reflection efficiency of a far end face of an optical fiber cable according to a second embodiment and a calculation result by an optical simulation simulating the tip end.

FIG. 4 is a diagram conceptually showing light ray reflection due to far-end reflection in a third embodiment.

FIG. 5 is a diagram showing a result of measuring a reflectance of a far end face of an optical fiber cable by roughening processing according to a third embodiment.

FIG. 6 is a diagram conceptually illustrating light ray reflection due to far-end reflection according to the fourth embodiment.

FIG. 7 is a diagram illustrating a calculation result by an optical simulation regarding a relationship between a reflectance of a far end face of an optical fiber cable and a radius of curvature of a concave end face according to a fourth embodiment.

FIG. 8 is a diagram conceptually illustrating light ray reflection due to near-end reflection according to the fifth embodiment.

FIG. 9 is a diagram illustrating an optical simulation calculation result of a relationship between the inclination angle of the truncated cone shape of the core and the near-end reflectance of the optical fiber cable when the radius of curvature of the convex surface of the end surface is changed according to the fifth embodiment.

FIG. 10 is a diagram showing an optical arrangement used for the simulation of FIG. 9;

FIG. 11 is a side sectional view of a main part for describing a method of processing an end face of an optical fiber cable according to a sixth embodiment.

FIG. 12 is a diagram conceptually illustrating light ray reflection due to near-end reflection according to the seventh embodiment.

FIG. 13 is a side sectional view of a main part for describing a method of processing an end face of an optical fiber cable according to a seventh embodiment.

FIG. 14 is a diagram conceptually showing an optical transmission / reception system using a conventional optical fiber cable.

FIG. 15 is a conceptual diagram for explaining a problem in a conventional optical fiber cable.

[Explanation of symbols]

 101, 105, optical transceiver 102, 106 connector 103, 107, 802, 1006, 1202 transmitting unit 104, 108, 801, 1007, 1201 receiving unit 109, 803, 1001 optical fiber cable 1102, 1302 heating plate 1104, 1304 core unit 1105, 1605 Plug part (covering member)

Continuation of the front page F term (reference) 2H036 JA05 KA03 2H037 BA02 BA11 CA06 CA08 2H038 CA23 2H050 AB42Z AC86 AC87

Claims (21)

[Claims] 1. An optical fiber cable comprising an end face for scattering reflected light on a core portion serving as a light transmission path. 2. The optical fiber cable according to claim 1, wherein said end surface is rough. 3. The optical fiber cable according to claim 2, wherein said end surface is a convex surface. 4. The optical fiber cable according to claim 3, wherein the radius of curvature of the convex surface of the end surface is 0.8d to 1.8d, where d is the diameter of the core. Fiber optic cable. 5. A core end face for transmitting light is convex.
An optical fiber cable, wherein the radius of curvature of the convex surface is 0.8d to 1.8d, where d is the diameter of the core. 6. An optical fiber cable, wherein an end surface of a core portion serving as a light transmission path has a concave surface. 7. The optical fiber cable according to claim 6, wherein the radius of curvature of the concave surface of the end face is 0.5d to 3.0d, where d is the diameter of the core. Fiber optic cable. 8. The optical fiber cable according to claim 1, wherein the distal end has a truncated cone shape in which the core extends toward the end surface, and the inclined portion has a truncated cone shape. And the horizontal part of the core is 30
An optical fiber cable characterized by being less than or equal to 60 ° or more than 60 °. 9. The optical fiber cable according to claim 1, wherein an inclined portion in which the core narrows toward an end face is formed at a distal end portion. . 10. The optical fiber cable according to claim 9, wherein at least a tip of said core portion is covered with a covering member, and a tip of said covering member is at an acute angle with respect to a central axis. An optical fiber cable, wherein the tip portion of the optical fiber cable is covered with the core portion to form the inclined portion that narrows toward the end surface. 11. A tip portion is formed in a truncated cone shape in which a core portion serving as a light transmission path spreads toward an end face, and an angle formed by an inclined portion of the truncated cone shape and a horizontal portion of the core portion is 30 °. An optical fiber cable characterized by being equal to or less than 60 °. 12. An optical fiber cable, wherein an inclined portion in which a core portion serving as a light transmission path narrows toward an end surface is formed at a distal end portion. 13. The optical fiber cable according to claim 12, wherein at least a distal end portion of a core serving as a light transmission path is covered with a covering member, and the leading end of the covering member forms an acute angle with respect to a central axis. An optical fiber cable characterized in that the tip portion of the covering member is covered by the core portion, whereby the inclined portion narrowing toward the end surface is formed. 14. The optical fiber cable according to claim 5, further comprising an end face for scattering the reflected light on said core portion. 15. The optical fiber cable according to claim 14, wherein said end surface is rough. 16. The optical fiber cable according to claim 2, wherein the end face has a roughness of 1 μm.
An optical fiber cable having a thickness of from 10 μm to 10 μm. 17. The optical fiber cable according to claim 1, wherein the optical fiber cable is used in a full-duplex optical communication system for transmitting and receiving bidirectional light with a single core comprising the core. Fiber optic cable. 18. An optical fiber cable which is used in a full-duplex optical communication system in which a core end surface serving as a light transmission path has a convex surface, and a single core comprising the core portion transmits and receives bidirectional light. 19. A method of processing an end surface of an optical fiber cable in which at least a periphery of a core portion made of a plastic material is covered with a covering member, wherein a truncated cone-shaped covering member in which an inner wall surface extends in a tip direction at the tip portion. The core is heated and deformed with the tip of the core protruding from the covering member, and the tip of the core spreads toward the end face, and the angle between the inclined portion and the horizontal portion of the core is 30. A method for processing an end face of an optical fiber cable, wherein the end face is processed into a truncated conical shape of not more than 60 ° or not less than 60 °. 20. A method of processing an end surface of an optical fiber cable in which at least a periphery of a core portion made of a plastic material is covered with a covering member, the covering member having a tip portion having an acute angle with respect to a central axis. An end face processing method for an optical fiber cable, wherein the core is heated and deformed in a state where the tip of the core projects further, and the end is processed so that the core covers the tip of the covering member. 21. The method for processing an end face of an optical fiber cable according to claim 19, wherein a heating plate is used to heat the core portion, and a shape formed on the heating plate is transferred to the core portion. And processing the end surface of the core portion into a convex surface, a concave surface, or a rough surface.