JPH047925A - Optical transmitter-receiver - Google Patents

Abstract

PURPOSE:To realize 2-way optical communication by providing a wavelength filter and input and output branching device in a ring laser loop and propagating a received light in the opposite direction to a stimulate light. CONSTITUTION:A received light R1 processed as a signal is inputted to an input output branching device 52 in an opposite direction to a stimulated light L1 through an optical fiber 52a. Then the received light R1 passes through the input output branching device 52 and only the reception light R1 of an equivalent wavelength to a set wavelength lambda at a wavelength filter 53 is selected and its received light R1 is propagated to a photodetector 55 via an output branching device 54. The stimulated light L1 generated by an amplifier 51 is inputted to the wavelength filter 53 via an isolator 50 and the output branching device 54. The stimulated light L1 inputted to the filter 53 is set to a setting wavelength and the result is outputted to an exchange station as a transmission light L2 through the optical fiber 52a from the branching device 52. On the other hand, part of the stimulated light L1 inputted to the branching device 52 is amplified by the amplifier 51 and outputted again to the isolator 50.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical transceiver used for optical wavelength division multiplexing communication capable of large-capacity communication in which light of different wavelengths is transmitted through the same optical fiber.

<Conventional technology> Conventionally, as a technology in this type of field, I.I.I. Communications Magazine (IEEE Com
(19)
89-3>P, 22-30.

As described in this document, in an optical communication system using a conventional optical wavelength multiplexing method, for example, there is one switching center and a two-way communication system with one end connected to the switching center via an optical multiplexer. It is equipped with an optical fiber for optical communication and a plurality of subscriber terminals branched and connected to the other end of the optical fiber via an optical multiplexer.

In this optical communication system, two wavelengths, one for transmission and one for reception, are assigned to each subscriber terminal.

When a subscriber terminal receives an optical signal from an exchange, the lights of different wavelengths output from the exchange are combined using an optical multiplexer, sent to one end of an optical fiber, and then sent out from the other end of the fiber. After the light is demultiplexed into light of different wavelengths by an optical demultiplexer, each subscriber terminal receives the light of a wavelength corresponding to the reception wavelength assigned to it.

Furthermore, when transmitting from a subscriber terminal to an exchange, the signal is modulated into an assigned transmission wavelength and output to the exchange.

(Problems to be Solved by the Invention) However, the optical transceiver having the above configuration has the following problems.

(1) The biggest challenge in wavelength division multiplexing communication in which light of different wavelengths is transmitted through the same optical fiber is to stabilize the wavelength spacing and the absolute value of the wavelength for each channel to a reference value. This stabilization requires large-scale equipment, such as a precision interferometer, and although such equipment can be installed at the switching center, it is impossible to install it at the general subscriber side. As a result, bidirectional optical communication could not be realized.

(2) Detection is usually based on coherent detection technology that utilizes the coherence of light. Coherent detection not only requires advanced technology, but also lacks a local oscillation light source that is stable and whose wavelength can be varied over a wide range, making multichannel detection difficult.

Due to the above (1) and (2>), there is a problem in that practical bidirectional optical communication cannot be realized by wavelength multiplexing.

The present invention provides an optical transceiver that solves the problem of the prior art, which is that bidirectional optical communication by wavelength multiplexing cannot be realized.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an isolator that allows only forward oscillation light to pass through, an isolator that inputs and propagates received light in a direction opposite to the oscillation light, and an input/output splitter that outputs transmitted light; an optical amplifier that amplifies both the oscillated light and the received light or only the oscillated light; and an optical amplifier that amplifies the oscillated light and the received light or only the oscillated light; The device includes a wavelength filter that generates the transmitted light by setting the wavelength to the wavelength, and a light receiver that converts the received light of the predetermined wavelength into an electrical signal.

(Function) Since the present invention has an optical transmitter/receiver configured as described above, the isolator is configured to allow only forward oscillation light to pass through and remove received light, reflected light, etc. in the opposite direction to stabilize laser oscillation. The input/output branching device inputs and propagates the received light in the opposite direction to the oscillated light, and outputs the transmitted light.

The optical amplifier sustains laser oscillation by amplifying both the oscillated light and the received light, or only the oscillated light. The wavelength filter is
Selecting received light of a predetermined wavelength in the received light,
The oscillation light is set to the wavelength to match the wavelengths of the received light and the transmitted light. The optical receiver converts received light of a selected predetermined wavelength into an electrical signal.

Therefore, the above problem can be solved.

(Embodiment) FIG. 1 is a block diagram of the configuration of an optical transceiver showing an embodiment of the present invention.

This optical transceiver is used for optical wavelength division multiplexing communication, and includes an isolator 50 that allows only forward oscillation light L1 to pass through. On the input side of this isolator 50, oscillation light L
1 and an optical fiber 52 from the switching center.
an input/output splitter 52 for inputting and propagating the received light R1 inputted through a in a direction opposite to the oscillation light L1 and outputting the transmitted light L2 to the optical fiber 52a;
An output branching device 54 is connected to a wavelength filter 53 that selects received light R1 of a predetermined wavelength in the wavelength filter 53 and sets the oscillated light L1 to the wavelength to generate transmitted light L2. Here, the amplifier 51 has a function of generating a signal for transmission by switching the oscillation light L1, and the wavelength filter 53 has a transmission band of 1 nm and a wavelength variable range of 1 nm.
This is a variable filter with high characteristics of about 100n.

Further, the output branching device 54 is connected to a light receiver 55 that converts the received light R1 of a predetermined wavelength selected by the wavelength filter 53 into an electrical signal, and an isolator 50 is also connected thereto. These isolators 50. Amplifier 51. Input/output branch 52. Wavelength filter 53. The output splitter 54 forms a ring laser loop in which the oscillation light l-river rotates in the 111α direction of the isolator 50.1. Amplifier 51. Input/output splitter 52, wavelength filter 53. Output splitter 54. The operation of the optical transmitter/receiver constructed as described above will be described below.

(A) Received light R1 converted into an operation signal at the time of reception is inputted into the input/output branching device 52 in the opposite direction to the oscillating light L1 from, for example, an exchange (not shown) through an optical fiber 52a. Then, the received light R1 having a plurality of wavelengths (signals) is transferred to the input/output splitter 52.
After passing through the wavelength filter 53, the set wavelength λ1
Only the received light R1 having a wavelength equivalent to is selected, and the selected received light R] is propagated to the light receiver 55 via the output splitter 54. However, a part of the received light R1 selected with a specific wavelength λIC travels in the direction R2 shown in FIG. 1, but is removed by the isolator 50. On the other hand, the received light R1 input to the light receiver 55 is converted into an electric signal by the light receiver 35. (B) Operation during transmission For example, the oscillated light L1 generated by the amplifier 5] is transmitted to the isolator 50. Wavelength filter 53 via output splitter 54
is input. The oscillated light L1 outputted from the wavelength filter 534 is set to have two wavelengths, and is output from the input/output branch 52 to the switching center through the optical fiber 52a as the transmitted light L2.

On the other hand, the specific wavelength λ1 input to the input/output splitter 52
A part of the oscillated light L1 is amplified by the sufficient amplification function of the amplifier 51 and outputted to the isolator 50 again. In this manner, the present device oscillates the ring laser loop at the set wavelength λ1. At this time, if the amplifier 51 generates a signal for transmission by switching the oscillation light L1,
This signal can be added to the transmission light L2.

Here, the wavelength filter 53 connects the oscillation light [,1 and the received light R1
Therefore, the wavelengths of the oscillated light L1 and the received light R1 completely match at the set wavelength λ1. Furthermore, since the wavelength of the received light R1- is stabilized at the telephone office, the wavelength of the transmitted light L2 is also stabilized.

This embodiment uses a high-performance variable filter with a narrow transmission band (lnm) and a wide wavelength variable range of 1100n, so the number of channels can be increased. Also,
Amplifier 51. Input/output branch 52. Wavelength filter 53.
Output splitter 54. Since the light receiver 55 and the light receiver 55 are integrally formed on a substrate such as a compound semiconductor, it is possible to downsize the device.

FIG. 2 is a schematic configuration diagram of an optical communication system showing an application example of the present invention.

This optical communication system is used for optical wavelength division multiplexing, and includes one switching center 60 and a plurality of subscriber terminals 70a to 70n having the same configuration as in FIG. The other end of the optical fiber 80 is connected to the subscriber terminals 7Q a to 70n via a branching device 90.
It is connected to the.

The branching device 90 distributes light into multiple directions 5, and is composed of, for example, a star coupler concentrating by passive branching (branching light without applying voltage).

The switching center 60 includes a plurality of transmitters 61a that convert electrical signals and generate received light R1 of different specific wavelengths λa to λn.
~61. n, a multiplexer 62 that multiplexes the outputs of the respective oscillators 61a to 61n, and an isolator 63 that allows only the output of the multiplexer 62 to pass. Here, transmitter 61. A to 61n are composed of semiconductor lasers and the like. A coupler 64 is connected to the output side of the isolator 63 and outputs the separated light at a predetermined ratio.One end of the coupler 64 is connected to the input side of a wavelength shift detector 65. This wavelength shift detector 65 has a predetermined wavelength reference λ0 in advance, collates this wavelength reference λO with the wavelength of the light from the coupler 64, and generates an electric signal S1 according to the collation result.
It has a function of transmitting the information to each of the transmitters 61a to 61n.

Further, the other end of the coupler 64 is connected to the input side of the duplexer 66, and the output side of the duplexer 66 is connected to a plurality of receivers 67a to 67.
n, respectively. This receiver 67a-67
n is composed of a falling wave diversity receiver, for example,
This optical communication system A, which has a function of receiving optical signals of specific wavelengths λa to λn together with the transmitters 6La to 61n, performs the following operations.

(A) Operation during reception For example, when transmitting a signal from the subscriber terminals 70a to 70n to the switching center 60, the amplifier 51, isolator 50, and output branching device 54 shown in FIG. , the wavelength filter 53, and the input/output splitter 52, the transmitted light L2 with specific wavelengths λa to λn is
The signal is input to the coupler 64 through an optical fiber 80. The input transmission light L2 is divided into wavelengths λa to λ by the demultiplexer 66.
4, where the transmitted light L2 is separated into wavelengths λa to λn and input into receivers 67a to 67n, respectively;
In the receivers 67a to 67n, the input wavelengths λa to λn
The transmitted light L2 is converted into an electrical signal.

(B) Operation at the time of transmission A plurality of received lights R1 having specific wavelengths λa to λn converted from electrical signals are sent to a transmitter 61 for each wavelength λa to λn.
．． a to 61T] is outputted to the multiplexer 62, then inputted to the splitter 9065 via the coupler 64 and the optical fiber 80, and distributed to each subscriber terminal 70a to 70n at the splitter 90. be done. Subscriber terminals 70a-7
0 n &, -, The input received light R1 passes through the input/output splitter 52, the wavelength filter 53, and the output splitter 54 shown in FIG.
They are converted into electrical signals corresponding to specific wavelengths λa to λn assigned to wavelengths 70n, respectively.

On the other hand, the - portion of the received light R1 inputted to the coupler 61 is inputted to the wavelength shift detector 65. In this wavelength shift detector 65, the wavelength of the input received light R1 is compared with the wavelength reference λ0, and a wavelength shift is detected. This detection result is converted into an electrical signal and fed back to each transmitter 61a to 61n as an electrical signal S16.
The transmitters 61a to 61n are controlled by the electric signal S1 so that the wavelengths λa to λn of the transmitted light L2 are constant.

In this application example, when a part of the input transmitted light L2 attempts to proceed to the multiplexer 62, the transmitted light L2 is blocked by the isolator 63. Each transmitter 61a-61. By inputting to n, it is possible to prevent the transmission from becoming unstable.

Note that the present invention is not limited to the illustrated embodiment, and various modifications are possible. For example, as a modification thereof, in the above embodiment, the amplifier 51 is provided between the isolator 50 and the input/output branch 52, but the invention is not limited to this. For example, the amplifier 51 is provided between the input/output branch 52 and the output branch It may be provided between. In this case, it becomes possible to amplify not only the oscillated light L1 but also the received light R1.

(Effects of the Invention) As described above in detail, according to the present invention, a wavelength filter and an input/output splitter are provided in a ring laser loop in which oscillated light is rotated in one direction, and the received light is converted into oscillated light. Since the received light is propagated in the opposite direction to the wavelength filter and then converted into an electrical signal, the wavelength can be easily stabilized and practical two-way optical communication can be achieved with simple technology and structure. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram of an optical transceiver showing an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of an optical communication system showing an application example of the present invention. 50...Isolator, 51...Amplifier, 52...Input/output branch, 53...
Wavelength filter, 54... Output splitter, 55...
...Receiver, R1...Received light, Ll...
...Oscillation light, L2...Transmission light.

Claims (1)

[Scope of Claims] An isolator that allows only forward oscillation light to pass through; an input/output splitter that inputs and propagates received light in a direction opposite to the oscillated light and outputs transmitted light; and the oscillated light. and an optical amplifier that amplifies both of the received light or only the oscillated light, and a wavelength filter that selects the received light of a predetermined wavelength in the received light and sets the oscillated light to the wavelength to generate the transmitted light. An optical transceiver comprising: and a light receiver that converts the received light of the predetermined wavelength into an electrical signal.