JPS58191543A - One-cored bidirectional optical communication system using same wavelength - Google Patents

Abstract

PURPOSE:To make a bidirectional module small-sized, lightweight and low-cost, by forming a photodetector section around a small circular light emitting section concentrically and incorporating the photodetector and the light emitting section. CONSTITUTION:The one-cored bidirectional communication system using the same wavelength consists of a one-cored optical fiber connecting two communicating points and a bidirectional module provided at both ends of the fiber. In the bidirectional module, the light emitting section 12 and the photodetector 13 are formed on a light emitting/photo detection base 15 concentrically. The section 12 is formed as a circle sufficiently smaller than the diameter (a) of a core 10a of an optical fiber 10. The section 13 is formed as a ring having an outer diameter (B) almost twice the diameter (a), by leaving a vacant region 14 for insulation around the section 12. The sections 12 and 13 are arranged at a distance D expressed as D=a/2X from the end 17 of the fiber 10, where X is the numerical aperture of the fiber 10. Thus, the input/output of optical signals to the fiber 10 is done with high efficiency and the bidirectional module is incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a same-wavelength single-core bidirectional optical communication system. Conventionally, when performing bidirectional communication using a negative-core optical fiber,
The following types of communication systems are used. 1st
The figure shows a same-wavelength single-core bidirectional optical communication system, with point A
Light of the same wavelength is used for the optical signal λ1A from B to A and the optical signal λIB from B to A. A bidirectional module (input/output device) 2a connected to the optical fiber 1.

In 2b, two optical paths are created using a coupler such as a half mirror or a Y branch, and the optical signal to be transmitted to fiber 1 is inserted from one optical path, and the optical signal transmitted through fiber 1 from the other optical path is inserted. It is designed to be taken out. Also the second
The system shown in the figure is called a wavelength multiplexing bidirectional optical communication system, in which the optical signal λIA from point A to B and the optical signal λ2B from B to A use lights of different wavelengths.

In this case as well, the bidirectional modules 4a and 4b connected to the optical fiber 3 are equipped with a half mirror, a Y branch, etc., and selectively separate and extract the optical signal transmitted from the other point. An optical demultiplexer is needed.

These communication systems differ in whether they use one or two wavelengths of light, but in either case, separate optical paths are required for inserting and extracting optical signals, so couplers and optical demultiplexers are required. Further, as a matter of course, the light emitting section and the light receiving section are provided separately. Therefore, the bidirectional module has the drawback that it is difficult to miniaturize it, and it becomes expensive.

The present invention has been made in view of such conventional difficulties, and its feature is that the light receiving part is formed concentrically around a small circular light emitting part, and the light receiving part and the light emitting part are integrated. .

The present invention will be described in detail below with reference to the drawings.

The method of the present invention for bidirectional optical communication with the same wavelength and one core is as follows:
As shown in FIG. 3, communication points A, Bf: a single optical fiber 1o for communication and bidirectional modules 11a, iib, ! installed at the terminals of the fiber. : Consists of.

As shown in FIG. 5, the bidirectional modules IIA and ILB include a light emitting unit 12 that converts an electrical signal into an optical signal and inserts it into the fiber 10, and a light emitting unit 12 that converts an optical signal emitted from the fiber 1° into an electrical signal. A light receiving/emitting part substrate 15 is formed concentrically with a light receiving part 13 to be taken out through an insulating air space 14.
It is equipped with

The light emitting section 12 of the substrate 150 consists of an LED (light emitting diode) or an LD (laser diode), and the light receiving section 1
3 is PIN-PD (PIN photodiode) or AP
D (avalanche photodiode), and has an integrated structure as shown in FIG. 6, for example. Here, reference numeral 21 denotes an N-type silicon substrate, the P layer formed thereon serves as the light-receiving section 13, and the layer including the GaAtAs layer 23 formed through the gold vapor deposited layer 22 in the center serves as the light-emitting section 13. It becomes.

Further, the light emitting/receiving portion substrate 15 includes a light emitting portion 12 and a light receiving portion 13.
A necessary electronic circuit 18 such as a drive circuit is formed,
The electric signal eA (eB) is transmitted to the light emitting unit 12 via the circuit 18.
The electric signal eB (eA) is supplied from the light receiving section 13 to
is taken out. This electronic circuit 16 can be formed into a hybrid IC and integrally formed with the light emitting section 12 and the light receiving section 13.

As shown in FIG. 4, this light emitting portion 12 is formed into a circular shape that is sufficiently smaller than the diameter a of the core 10a of the fiber 10. Further, the light receiving section 13 is formed into an annular shape having an outer diameter B that is approximately twice the core outer diameter a, leaving an air space 14 around the light emitting section 12. The light emitting section 12 and the light receiving section 13 are insulated by an air space 14. When the numerical aperture NA of the fiber 10 is set to
The light emitting parts 12 are arranged in parallel so that the center of the light emitting part 12 is located on an extension of the optical axis 16 at a distance of 2X.

Here, the light λ that comes out from the center of the light emitting section 12 and enters the end of the core surface 17a of the fiber end face 17 becomes F. This numerical aperture X is, for example, 0.2 for a silica glass optical fiber. Since the value is as small as 0.3 for an optical fiber made of multi-component glass, the equation (2) is obtained. Therefore, the circular light emitting part 1 that is sufficiently smaller than the core diameter a is arranged at a distance of D = a/2X.
Of the light emitted from 2, the core surface 17a of the fiber end surface 17
All the light incident on the core 10a is combined and propagated through the core 10a.

On the other hand, if the light emitted from the dance part of the core surface 17a is λ', it is emitted at θmax with respect to the normal to the core surface, so 1,', B = 2a...
・・・・・・・・・・・・■. Therefore fiber 10
The light that has propagated through the core 4, which is located at a distance of D, has a diameter of a.
The light is almost completely received and extracted by the annular light-receiving section 13, which has an outer diameter twice as large as the outside diameter.

In this way, by arranging the circular light emitting part 12, which is sufficiently smaller than the core diameter a, and the annular light receiving part 13, which has an outer diameter of 2a, concentrically at a distance of D = a/2X from the fiber end face 17, It becomes possible to input and output optical signals to and from a fiber with high efficiency, and to integrate separate bidirectional modules with a light emitting section and a light receiving section.

FIG. 5 shows the bidirectional module 11a (Ilb), in which the end of the fiber 10 is placed opposite the light emitting part 12 and the light receiving part 13 through the receptacle 18 of the casing housing the light emitting/receiving part board 15, and the fiber is A plug 19 attached to the fiber 10 is screwed onto the outer periphery of the receptacle 18, and the fiber 10 is attached to the module 11a (11b).

Fiber end and light emitting section 12. It is directly connected to the light receiving section 13 using a transparent resin 20 such as epoxy.

By structuring the bidirectional module like this,
By attaching it to the end of the fiber 10, the fiber end 17, the substrate 150, the light emitting section 12, and the light receiving section 13 can be easily arranged in a predetermined relationship.

As explained above, in the present invention, a light emitting part is formed in a circular shape sufficiently small with respect to the core diameter of the optical fiber, and a light receiving part having a predetermined outer diameter is formed concentrically around this light emitting part. By integrating the two light-emitting parts and placing them in a fixed positional relationship with respect to the fiber end face, we are able to transmit and receive optical signals, making it possible to simultaneously communicate with both the same wavelength and the same wavelength with good coupling efficiency without the need for an optical coupler. I can do it. Furthermore, since a bidirectional module can be realized in one set, it is small, lightweight, and low cost, and the optical coil/lid can also be simplified.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams for explaining the conventional single-core bidirectional optical communication system, FIG. 3 is an explanatory diagram for explaining the same-wavelength single-core bidirectional optical communication system of the present invention, and FIG. Figure (a), (
b) is a perspective view and a sectional view showing the positional relationship between the end of the optical fiber and the light receiving/emitting unit substrate used in the present invention, and FIG. 5 is an explanatory view showing how the optical fiber is connected to the bidirectional module; FIG. 6 is a sectional view showing the light receiving and emitting section. io・=optical fiber, 10a...core, 113, 1
1b...Bidirectional module, 12...Light emitting part, 13
. . . Light receiving portion, 14 . a...Core diameter,
...Maximum acceptance angle of optical fiber. Agent Patent Attorney Moritani -O

Claims (1)

[Claims] In a same-wavelength single-core bidirectional optical communication system in which two communication points are connected by an optical fiber and signals are sent and received between the points using optical signals of the same wavelength, the optical fiber has a core Vkm, an open wavelength Consisting of several X optical fibers, the shoulder surfaces at both ends are exposed perpendicular to the optical axis, and the bidirectional module installed at both ends of the X fibers has a diameter sufficiently smaller than the core diameter a. The outer diameter of the circular light emitting part and the outer diameter of the circular light emitting part leaving an insulating round air space around the light emitting part is the core diameter a.
The light emitting part and the light receiving part are arranged parallel to each other with their centers aligned at a distance of a/2X with respect to the end surface of the optical fiber. Features a same-wavelength, single-core bidirectional optical communication system.