WO2003103194A1

WO2003103194A1 - Bidirectional optical transmission system and optical transmission/reception device

Info

Publication number: WO2003103194A1
Application number: PCT/JP2003/006530
Authority: WO
Inventors: 加藤　和利; 山林　由明; 昇石原; 俊一東野; 由一千葉; 鈴木　安弘
Original assignee: エヌティティエレクトロニクス株式会社
Priority date: 2002-05-27
Filing date: 2003-05-26
Publication date: 2003-12-11
Also published as: JPWO2003103194A1; JP4369363B2; AU2003241767A1

Abstract

The optical transmission circuit of a slave device needs no light emitting element, and there is no need to control or maintain, with very high precision, the wavelength of the light emitting element in the optical transmission circuit of a slave device. In a bidirectional optical transmission system for allowing bidirectional transmission between a main device and a slave device, the main device comprises an optical transmission circuit for transmitting, to the slave device, a downstream optical signal obtained by superimposing a bias component on a signal component modulated with a downstream signal; and an optical reception circuit for detecting an upstream signal from an upstream optical signal transmitted from the slave device. The slave device comprises an optical reception circuit for detecting a signal component from a downstream optical signal transmitted from the master device; and an optical transmission circuit for transmitting, to the main device, an upstream optical signal obtained by modulating a part of a downstream optical signal with an upstream signal by use of a saturated amplification/attenuation circuit.

Description

Specification

Bidirectional optical transmission system and optical transceiver

The present invention relates to a bidirectional optical transmission system for bidirectionally transmitting an optical fiber between a master device and a slave device, and an optical transceiver. Background art

Figure 16 shows the configuration of a conventional bidirectional optical transmission system. In FIG. 16, 15-1 and 15-2 are optical fibers, 41 is an optical transmission circuit of a main unit, 42 is an optical receiving circuit of a main unit, 43 is an optical receiving unit, and 44 is an optical transmission unit. Reference numeral 48 denotes an optical receiving circuit of the slave device, and 49 denotes an optical transmitting circuit of the slave device.

The configuration of the bidirectional transmission method between the master device and the slave device is described with reference to Fig. 16 (a). Figure 16 shows a bidirectional optical transmission system in which bidirectional transmission is performed between a master device and a slave device using a two-core optical fiber. That is, as shown in FIG. 16 (a), between the optical transmission circuit 41 of the main device and the optical reception circuit 48 of the slave device, and between the optical transmission circuit 49 of the slave device and the optical reception circuit of the master device. 4 and 2 are connected by two-core optical fibers 15 _ 1 and 15 _ 2 to perform bidirectional transmission. In FIG. 16 (a), the optical transmission circuit 41 of the main unit transmits a downstream optical signal through the optical fiber 15-1, and the optical reception circuit 48 of the slave unit receives the downstream optical signal. The optical transmission circuit 49 of the slave device transmits an upstream optical signal through the optical fiber 15-2, and the optical reception circuit 42 of the master device receives the upstream optical signal. FIG. 16 (b) shows a head-end configuration of the optical receiving circuit 48 and the optical transmitting circuit 49 of the slave device. In FIG. 16 (b), in the optical receiver circuit 48 of the slave device, the downstream optical signal received via the optical fiber 15-1 is detected by the optical receiver 43, and the detected downstream signal is transmitted to the optical receiver 43. The signal is processed in the receiving circuit 48. On the other hand, the upstream signal is modulated into an upstream optical signal by the optical transmitter 44. The modulated upstream optical signal is transmitted through the optical finos I5-2. The operation of transmitting and receiving an upstream optical signal or downstream optical signal is shown in FIG. In FIG. 17, the light-emitting element is driven by the drive current of the downstream signal in the optical transmission circuit of the main device (FIG. 17 (a)). The light output of the light-emitting element is almost linearly related to the drive current (Fig. 17 (b)). As a result, the optical transmission circuit of the main unit transmits the downstream optical signal output close to the waveform of the downstream signal (Fig. 17 (c)). In the optical receiver circuit of the slave device, a threshold is set for the signal component input to the optical receiver circuit, and a downstream signal is detected (Fig. 17 (d)). The same applies to the operation of the optical transmission circuit of the slave device and the operation of the optical reception circuit of the master device. That is, the optical transmission circuit of the master device and the optical transmission circuit of the slave device must each have a light emitting element.

Fig. 18 shows the configuration of another conventional bidirectional transmission system. This configuration is a bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength-division multiplexed multipoint transmission is performed between a main device and a plurality of slave devices. In Fig. 18, 4 1 — 1 to 4 1 — N is the optical transmission circuit of the main unit, 4 2 — 1 to 4 2 — N is the optical receiving circuit of the main unit, 4 5 — 1 and 4 5 _ 2 are the main unit. 15-1 and 15-2 are optical fibers, 16-1 and 16-2 are wavelength multiplex circuits provided in the middle of the optical fiber, and 48-8 :! ~ 48 — N is the optical receiving circuit of the slave, 49 1:! 449-N is the optical transmission circuit of the slave device. Here, the symbol N is used to represent two or more. For example, optical transmission circuit 4 1 1; 44 1 —N represents two or more optical transmission circuits.

The configuration of a system for performing bidirectional transmission between a main device and a plurality of slave devices will be described. In FIG. 18, a plurality of optical transmission circuits 4 1-1 to 4 1 1 N of the main unit transmit wavelengths (A ₁ λ ₂ ,...) Assigned to respective downstream optical signals modulated by the downstream signals. At λ)), the signal is transmitted to the wavelength multiplexing circuit _45-1 of the main device. The wavelength division multiplexing circuit 45-1 multiplexes downstream optical signals of different wavelengths transmitted from a plurality of optical transmission circuits onto the optical fiber 115-1. The wavelength multiplexing circuit 16-1 provided in the middle of the optical fiber 15-1 separates each downstream optical signal toward each slave device according to the wavelength. Optical receiving circuit of each slave device 4 8 — 1 to 4 8 — N detect signal components from the downstream optical signal received through the optical fiber 15-1. On the other hand, the optical transmission circuits 49-1 to 49-1 N of the respective slave devices transmit the upstream optical signals modulated by the upstream signals to the optical fibers 15-2. A wavelength multiplexing circuit 16-2 provided in the middle of the optical fiber 15-2 is a plurality of optical transmitting circuits 49-:! ~ 49-N, each of which has a wavelength (A i, λ ₂ , _... λ)) are wavelength-multiplexed toward the main unit. The wavelength multiplexing circuit 45-2 of the master device is a pre-assigned wavelength (λ; ^ λ ₂ , · · λ _た) transmitted from the optical transmission circuits 49-1 to 49-の of the slave devices. ) Is wavelength-separated for each wavelength toward the optical receiver circuit 42-1 to 42_Ν of the main device. Each of the plurality of optical receiving circuits 42-1 to 42-の of the main device detects an upstream signal from the received upstream optical signal. Here, each of the optical transmission circuits 49_1 to 49_Ν of the slave device must transmit an upstream optical signal of a predetermined wavelength. Optical transmission circuit of each slave device 49 1 ~ 49_Ν must each have a light emitting element, and furthermore, it is necessary to control or maintain the wavelength of these light emitting elements with high precision. Slave devices are generally distributed at different locations, and therefore have different environmental temperatures. When the wavelength of the light-emitting element shifts from a predetermined value due to a change in environmental temperature, light loss occurs in the wavelength multiplexing circuit 16-2 in the optical fiber 15-2 and the wavelength multiplexing circuit 45-2 in the main unit. Increase. Furthermore, if the transition is large, transmission may not be possible.

In order to solve such a problem, the present invention eliminates the need for a light emitting element in the optical transmission circuit of the slave device, and controls or maintains the wavelength of the light emitting element with high accuracy in the optical transmission circuit of the slave device. The purpose is to make it unnecessary.

Conventionally, semiconductor optical amplifier circuits (eg, T. Mukai and T. Saitoh, “5.2 dB noise figure in a 1.5 μm InGaAsP traveling wave laser amplifier”, Electron. t., Vol.23, No.5, pp.216-218 (1987)). This is a semiconductor optical amplifier circuit in which the waveforms of the input optical signal and the output optical signal have a linear relationship. Disclosure of the invention

In order to achieve the above-mentioned object, the first invention of the present application is a bidirectional optical transmission system in which a two-core optical fiber is bidirectionally transmitted between a master device and a slave device using a first optical fiber and a second optical fiber. An optical transmission circuit for transmitting, to the first optical fiber, a downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal, and the second optical fiber; An optical receiving circuit for detecting an upstream signal from an upstream optical signal received through the optical fiber, wherein the slave device detects the signal component from the downstream optical signal received through the first optical fiber; and An optical transmission circuit for transmitting the upstream optical signal, which is obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit, to the second optical fiber, Two-way light transmission Square Mel by formula.

The second invention of the present application is a bidirectional optical transmission system for performing directional multiplex bidirectional transmission between a master device and a slave device using a single-core optical fiber, wherein the master device converts a signal component modulated by a downstream signal into a signal component. An optical transmission circuit for transmitting a downstream optical signal having a bias component superimposed thereon toward the optical fiber; and an optical receiving circuit for detecting an upstream signal from an upstream optical signal received through the optical fiber. An optical receiving circuit for detecting the signal component from the downstream optical signal received through the optical fiber; and an upstream optical signal obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit. And a light transmission circuit for transmitting the light toward the optical fiber.

The third invention of the present application is a two-way optical transmission system in which the main device and the slave device are two-way multiplexed bidirectionally transmitted by a single optical fiber between the master device and the slave device. Wherein the saturation amplification / attenuation circuit is a semiconductor optical amplifier, and a film having a higher reflectivity than a cleavage state is coated on an end surface facing the incident end surface of the down optical signal, The fourth invention of the present application, which is a bidirectional optical transmission system characterized by a reflection type configuration in which a signal is transmitted from an incident end face of a signal, comprises a first optical fiber between a master device and a plurality of slave devices. A two-core optical fiber bi-directional wavelength-division multiplexing multi-point transmission using a second optical fiber and a second optical fiber, wherein the main unit is configured to superimpose a bias component on a signal component modulated by a downlink signal. A plurality of optical transmission circuits for transmitting an optical signal toward the first optical fiber; anda plurality of optical reception circuits for detecting an upstream signal from each upstream optical signal received through the second optical fiber, The compound Each of the slave units includes: an optical receiving circuit that detects the signal component from the downstream optical signal received through the first optical fiber; and a saturation amplification / attenuation unit that partially amplifies the received downstream optical signal. An optical transmission circuit for transmitting the upstream optical signal modulated by the upstream signal to the second optical fiber by a circuit.

A fifth invention of the present application is a bidirectional optical transmission system in which a main device and a plurality of slave devices are transmitted in a single-core optical fiber in a multiplexed bidirectional / wavelength multiplexed multipoint manner, wherein the main device is a downstream signal. A plurality of optical transmission circuits for transmitting, to the optical fiber, respective downstream optical signals in which a bias component is superimposed on a modulated signal component; and an upstream signal from each upstream optical signal received through the optical fiber. A plurality of optical receiving circuits for detecting, the plurality of slave devices each comprising: an optical receiving circuit for detecting the signal component from the downstream optical signal received through the optical fiber; and An optical transmission circuit for transmitting, toward the optical fiber, the upstream optical signal obtained by modulating a part of the signal with the upstream signal by a saturation amplification / attenuation circuit. Optical transmission This is the transmission method.

The sixth invention of the present application is the bidirectional optical transmission system according to the fifth invention, in which a master device and a plurality of slave devices are transmitted in a direction-multiplexed bidirectional one-wavelength multiplex multipoint manner using a single optical fiber. An attenuating circuit, which is a semiconductor optical amplifier, which coats a film having a higher reflectivity than a cleavage state on an end surface facing the incident end surface of the downstream optical signal, from the incident end surface of the downstream optical signal; This is a bidirectional optical transmission system characterized by a reflection type configuration for transmission.

A seventh invention of the present application is directed to a bidirectional optical fiber bidirectional / wavelength-time-division multiplexed bidirectional transmission between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber. In the transmission method, the master device separates each downstream optical signal obtained by superimposing a bias component on a signal component modulated by a downstream signal into a wavelength and a time domain for each slave device and directs the separated downstream optical signal to the first optical fiber. An optical transmission circuit for transmitting an optical signal, and at least one optical receiving circuit for detecting an upstream signal from each of the upstream optical signals received through the second optical fiber. An optical receiving circuit that detects the signal component from the downstream optical signal received through the first optical fiber; anda part of the received downstream optical signal is modulated with the upstream signal by a saturation amplification / attenuation circuit. I An optical transmission circuit for transmitting the upstream optical signal to the second optical fiber.

The eighth invention of the present application is a two-core optical fiber bidirectional / wavelength time-division multiplexing multi-point optical system using a first optical fiber and a second optical fiber between a master device and a plurality of slave devices according to the seventh invention of the present application. In the bidirectional optical transmission system for transmission, a wavelength tunable light source capable of changing the wavelength of an optical output to the wavelength of each slave device is used for the optical transmission circuit.

The ninth invention of the present application is directed to a bidirectional optical system in which a main unit and a plurality of slave units are transmitted in a single-core optical fiber in a direction-division multiplexed / wavelength time division multiplexed multipoint transmission. In the transmission method, the master device separates each downstream optical signal obtained by superimposing a bias component on a signal component modulated by a downstream signal into a wavelength and a time domain for each slave device and transmits the separated optical signal to the optical fiber. An optical transmitting circuit, and at least one optical receiving circuit that detects an upstream signal from each upstream optical signal received through the optical fiber, wherein the plurality of slave devices each receive the downstream signal received through the optical fiber. An optical receiving circuit for detecting the signal component from the optical signal; and transmitting the upstream optical signal, which is obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit, toward the optical fiber. A bidirectional optical transmission system characterized by comprising an optical transmission circuit.

A tenth invention of the present application is the ninth invention of the present application, wherein the main device and the plurality of slave devices are transmitted in a single-core optical fiber in a directional multiplex bidirectional / wavelength time division multiplex multipoint transmission system. A saturating amplification / attenuation circuit, which is a semiconductor optical amplifier, wherein a coating having a higher reflectivity than a cleavage state is coated on an end face opposed to an incident end face of the downstream optical signal; This is a bidirectional optical transmission system that is characterized by a reflection-type configuration for transmission from an optical network.

An eleventh invention of the present application relates to a ninth invention of the present invention, which relates to a bidirectional optical transmission system in which a main device and a plurality of slave devices are transmitted in a direction multiplexed bidirectional / wavelength time division multiplexed multipoint using a single optical fiber. A bidirectional optical transmission system, characterized in that a wavelength-variable light source capable of changing a wavelength of an optical output to a wavelength of each slave device is used for the optical transmission circuit.

A twelfth invention of the present application is directed to an optical transmission system for transmitting a second optical signal, which is obtained by modulating a part of a received first optical signal with a second transmission signal by a saturation amplification / attenuation circuit, to an optical fiber. An optical transmission circuit for transmitting a first optical signal in which a bias component is superimposed on a signal component modulated by a first transmission signal to an optical transmitting and receiving apparatus having a circuit; and the second optical signal received through an optical fiber. An optical transmitting and receiving apparatus comprising: an optical receiving circuit that detects a signal component from a signal. A thirteenth invention of the present application is directed to an optical receiving circuit for receiving an optical signal obtained by superimposing a bias component on a signal component modulated by a signal through an optical fiber, and a part of the optical signal received by a saturation amplification / attenuation circuit. An optical transmitting and receiving apparatus comprising: an optical transmitting circuit that modulates a signal to be transmitted and transmits the modulated signal to an optical fiber.

The fourteenth invention of the present application is the optical transmission / reception device according to the twelfth invention, wherein the bias component is at least 50%, preferably at least 100% of the signal component. An optical transceiver.

The fifteenth invention of the present application is the optical transmission / reception device according to the thirteenth invention of the present application, wherein the saturation amplification / attenuation circuit modulates an optical signal with an amplification unit that controls an amplification degree by a control current and a signal to be transmitted. An optical transmitting and receiving apparatus characterized by being a semiconductor optical amplifier having a modulating unit for performing the operation.

The sixteenth invention of the present application is the optical transmission / reception device according to the thirteenth invention of the present application, wherein the saturation amplification / attenuation circuit includes an amplification unit that saturates with a control current and a modulation that absorbs an optical signal with a signal to be transmitted. And a semiconductor optical element having a portion.

Note that these configurations can be combined as much as possible.Here, the saturation amplification / attenuation circuit linearly amplifies in the range where the optical input is small. This is a circuit where the light output is constant regardless of the level. Further, the amplification degree is controllable, so that the amplification degree can be increased to perform saturation amplification, or conversely, the amplification degree can be suppressed and attenuated. Note that the attenuation in the saturation amplification / attenuation circuit includes that in which the degree of amplification is simply reduced.

Two-core optical fiber bidirectional transmission refers to a technology for bidirectional transmission using a first optical fiber for transmitting downstream optical signals and a second optical fiber for transmitting upstream optical signals. Single-core optical fiber direction multiplex bidirectional transmission means that the same optical fiber is used for transmission of downstream optical signals and upstream optical signals, and an optical multiplexing / branching circuit is used to join and branch downstream optical signals and upstream optical signals having the same wavelength. Profit Is a technology for bi-directional transmission.

Two-core optical fiber bidirectionalWavelength multiplexing multipoint transmission refers to a transmission method in which a main unit and a plurality of slave units are connected in a 1-to-N multipoint connection, and the first optical fiber is used to transmit downstream optical signals. The second optical fiber is used for transmission of the upstream optical signal, and different wavelengths are assigned to the upstream optical signal and the downstream optical signal for each slave device. This is a technology to perform bidirectional transmission by wavelength multiplex transmission between them. Single-core optical fiber direction multiplexing bidirectional / wavelength multiplexing multipoint transmission refers to the transmission of downstream optical signals and the transmission of upstream optical signals in a transmission system in which a main unit and a plurality of slave units are connected in a 1: N multipoint connection. The same optical fiber is used, the upstream optical signal and the downstream optical signal have the same wavelength, and different wavelengths are assigned to each slave device, and wavelength multiplex transmission is performed between the main device and the wavelength multiplexing circuit provided in the optical fiber. This is a technology for bidirectional transmission.

Two-way optical fiber bi-directional wavelength-division multiplexing multipoint transmission is a transmission method in which a master unit and a plurality of slave units are connected in a 1: N multipoint connection. The second optical fiber is used for transmission of the upstream optical signal, and a different wavelength and time domain are assigned to each of the slave optical devices for the upstream optical signal and the downstream optical signal. This is a technology that performs wavelength multiplex transmission between provided wavelength multiplexing circuits and bidirectional transmission. Single-core optical fiber direction multiplexing bidirectional · Wavelength time division multiplexing multipoint transmission refers to the transmission of downstream optical signals and upstream optical signals in a transmission system in which a master unit and multiple slave units are connected in a 1: N multipoint connection. The same optical fiber is used for transmission, the upstream optical signal and the downstream optical signal have the same wavelength, and a different wavelength and time domain are assigned to each slave device. This is a technology for bidirectional transmission by wavelength multiplex transmission between circuits.

Here, the term “down” refers to a signal flow from the master device to the slave device, and the term “up” refers to a signal flow from the slave device to the master device. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.

FIG. 2 is an operation diagram of the bidirectional optical transmission system of the present invention.

FIG. 3 is an operation diagram of the bidirectional optical transmission system of the present invention.

FIG. 4 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.

FIG. 5 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.

FIG. 6 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.

FIG. 7 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.

FIG. 8 is a schematic structural diagram of an output intensity saturated amplification modulator according to an embodiment of the present invention.

FIG. 9 is a schematic structural diagram of an output intensity saturated amplification modulator showing an embodiment of the present invention.

FIG. 10 is a schematic sectional view of an output-intensity-saturated amplification modulator with a reflective film according to an embodiment of the present invention.

FIG. 11 is a schematic sectional view of an output-intensity-saturated amplification modulator with a reflective film according to an embodiment of the present invention.

FIG. 12 is a configuration diagram of an optical transmitting and receiving apparatus including an output intensity saturated amplification modulator with a reflection film.

FIG. 13 is a schematic structural diagram of an output intensity saturated amplification modulator showing an embodiment of the present invention.

FIG. 14 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.

FIG. 15 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention. It is.

Figure 16 is a block diagram of a conventional bidirectional optical transmission system.

Figure 17 is an operation diagram of the conventional bidirectional optical transmission system.

FIG. 18 is a configuration diagram of a conventional bidirectional optical transmission system. The description of reference numerals in the figure is as follows. 1 1, 1 1 — 1, 1 1 1 2, 1 1 1 N is the optical transmission circuit of the main unit, 1 2, 1 2 — 1, 1 2 — 2, 1 2 1 N is the optical reception circuit of the main unit, 1 3, 1 3-1, 1 3 _ 2 are main unit wavelength multiplexing circuits, 14, 14-1, 14-2, 14 4 N are main unit optical coupling / branching circuits, 15, 1 5-1, 15-2 is an optical fiber, 16-16 is 1, 1-16 is a wavelength division multiplexing circuit, 17-17-1, 17-2, 17-1 N is a slave device Optical coupling / branching circuit, 18, 18-1, 18-2, 18 -N is the optical receiving circuit of the slave device, 19, 19-1, 19-2, 19-1 N is the slave device An optical transmission circuit, 21 is an optical branching circuit, 22 is an optical receiving unit, 23 is a driving unit, 24 is an output intensity saturated amplification modulator, 25 is an optical transmission circuit of the main unit, and 26 is a main unit. Optical receiving circuit, 3 1 is an output intensity saturated amplification modulator, 3 2 is an output intensity saturation amplification modulator, 3 3 is an amplification modulation section,

3 4 is an output port, 3 5 is an amplifying section, 3 is a modulating section, 3 7 is an output intensity saturated amplifying modulator with a reflective film, 3 8 is an output intensity saturated amplifying modulator with a reflective film, 3 9 Is the entrance / exit port, 40 is the reflective film, 41, 4 1-1, 41-2, 41-N is the optical transmission circuit of the main unit, 42, 42-1, 42-2, 4 2—N is the optical receiving circuit of the main unit, 43 is the optical receiving unit, 44 is the optical transmitting unit, 45-1, 45-2 is the wavelength multiplexing circuit of the main unit, 48, 48-1, 4 8—2, 48_N is the optical receiver circuit of the slave device, 49, 49−1, 49−2, 49−1 N is the optical transmitter circuit of the slave device, and 61 is the output intensity saturated amplifier The modulator, 62 is a saturation amplification section, 63 is a modulation section, 64 is a semiconductor active layer, and 65 is an absorption modulation layer. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not construed as being limited to these embodiments.

(Embodiment 1)

The present embodiment is a bidirectional optical transmission system for bidirectional transmission of a two-core optical fiber. FIG. 1 shows the configuration of the embodiment of the present invention. In FIG. 1, 11 is an optical transmission circuit of the main unit, 12 is an optical receiving circuit of the main unit, 15-1 and 15-2 are optical fibers, 18 is an optical receiving circuit of the slave unit, and 19 is an optical receiving circuit of the slave unit. 21 is an optical splitter / branch circuit, 22 is an optical receiver, 23 is a drive unit, and 24 is an output intensity saturated modulator as a saturation amplification / attenuation circuit. .

The configuration of the method for bidirectional transmission between the master device and the slave device will be described with reference to Fig. 1 (a). In FIG. 1 (a), the optical transmission circuit 11 of the main unit transmits a downstream optical signal through the optical fiber 15-1, and the optical reception circuit 18 of the slave unit receives the downstream optical signal. The optical transmission circuit 19 of the slave device transmits an upstream optical signal through the optical fiber 15-2, and the optical reception circuit 12 of the master device receives the upstream optical signal. Fig. 1 (b) shows the head-end configuration of the optical receiving circuit # 8 and the optical transmitting circuit 19 of the slave device. In FIG. 1B, in the optical receiving circuit 18 of the slave device, the downstream optical signal received via the optical fiber 15-1 is split into two by the optical splitting circuit 21. The branched downstream optical signal is detected by the optical receiving unit 22, and the detected downstream signal is subjected to signal processing in the optical receiving circuit 18. The output intensity saturated amplification modulator 24 saturates and attenuates a part of the branched down optical signal with the up signal from the drive unit 23, and modulates it into the up optical signal. The modulated upstream optical signal is transmitted via the optical finos I5-2.

Next, the operation in this configuration will be described. Figure 2 shows the transmission and reception operations of the downstream optical signal, and Figure 3 shows the transmission and reception operations of the upstream optical signal. In FIG. 2, in the optical transmission circuit of the main device, a bias component is superimposed on a signal component modulated by a downstream signal to obtain a drive current for a light emitting element (FIG. 2 (a)). The light output of the light-emitting element has a substantially linear relationship with the drive current ( Figure 2 (b)). As a result, the optical transmission circuit of the main unit transmits a downstream optical signal output close to the drive current waveform (Fig. 2 (c)). In the optical receiver circuit of the slave device, a threshold is set for the signal component of the optical receiver circuit input, and the signal component of the downstream signal is detected (Fig. 2 (d)). Here, an example is shown in which the downlink signal is transmitted and received after being intensity-modulated, but may be a modulation format such as phase modulation or frequency modulation. Even in these modulation formats, the optical transmission circuit of the main device transmits a signal component with a bias component superimposed thereon, and the optical reception circuit of the slave device detects a downstream optical signal component from the signal component.

In Fig. 3, a part of the downstream optical signal is branched and input to the output intensity saturated amplifier (Fig. 3 (a)). The output-saturation-type amplifying modulator performs linear amplification in the range where the optical input is small, but as the optical input increases, the amplification level saturates and the optical output becomes constant regardless of the optical input level (Fig. 3 (b)). . Furthermore, the output intensity saturation amplification modulator is an amplification modulator whose amplification degree can be controlled from the control terminal.It can increase the amplification degree and perform the saturation amplification, or conversely, suppress the amplification degree and attenuate it. (Fig. 3 (b)). When the downstream optical signal branched into the output intensity saturation type modulator is input, the bias component is amplified by the saturation amplification because the bias component is superimposed on the signal component of the downstream optical signal, and the signal component is compressed. (Fig. 3 (c)). Furthermore, when an upstream signal from the drive unit of the optical transmission circuit of the device is input to the control terminal of the output intensity saturation amplification modulator, the amplification degree is controlled according to the upstream signal. As a result, the bias component is generated during the saturation amplification. A high-output optical signal that is amplified and the signal component is compressed is output, and a low-output optical signal is output in which both the bias component and the signal component are compressed during attenuation when the amplification is suppressed (Fig. 3 ( c)). The optical receiver circuit of the main unit sets a threshold value for the signal component input to the optical receiver circuit and detects the signal component of the upstream optical signal (Fig. 3 (d)).

Here, if the bias component is 50% or more of the signal component, and if the mark rate of the intensity-modulated signal is 50% duty, the optical power of the bias component is equal to or more than the average optical power of the signal component. Become out It becomes easy to amplify the bias component by the power intensity saturation type amplification modulator. When the bias component is equal to or more than 100% of the signal component, the optical power of the bias component becomes equal to or higher than the peak optical power of the signal component, and the bias component is amplified by the output intensity saturated amplification modulator. Becomes easier. The same applies to the following embodiments.

As described above, the optical transmission circuit of the main device transmits the downstream optical signal in which the bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and the optical transmission circuit of the slave device receives one of the received downstream optical signals. By transmitting an upstream optical signal whose section is modulated by an upstream signal by a saturation amplification / attenuation circuit, the slave device was able to perform bidirectional transmission without using a light emitting element.

(Embodiment 2)

The present embodiment is a bidirectional optical transmission system in which directional multiplex bidirectional transmission is performed using a single-core optical fiber. FIG. 4 shows the configuration of the embodiment of the present invention. In FIG. 4, 11 is the optical transmission circuit of the main device, 12 is the optical receiving circuit of the main device, 14 is the optical coupling / branching circuit of the main device, 15 is an optical fiber, 17 is the optical coupling / branching circuit of the slave device, 18 is the optical receiver circuit of the slave device, 19 is the optical transmitter circuit of the slave device, 21 is the optical branching circuit, 22 is the optical receiver, 23 is the driver, 24 is the saturation amplification / attenuation circuit. This is an output intensity saturated amplification modulator.

Fig. 4 (a) shows the configuration of the bidirectional transmission method between the master device and the slave device. In FIG. 4 (a), the optical transmission circuit 11 of the main unit transmits a downstream optical signal through the optical coupling / branching circuit 14 of the main unit and the optical fiber 15, and the optical reception circuit 18 of the slave unit is connected to the slave unit. The downstream optical signal is received through the optical coupling / branching circuit 17. The optical transmission circuit 19 of the slave device transmits an upstream optical signal through the optical multiplexer / demultiplexer circuit 17 of the slave device and the optical fiber 15, and the optical receiver circuit 12 of the main device transmits the upstream optical signal through the optical multiplexer / demultiplexer circuit of the master device. Receive the signal. FIG. 4 (b) shows the head-end configuration of the optical receiving circuit 18 and the optical transmitting circuit 19 of the slave device. In Fig. 4 (b), In the optical receiving circuit 18 of the device, the downstream optical signal received by the optical branching circuit 21 via the optical combining / branching circuit 17 of the slave device is branched into two. The branched down optical signal is detected by the optical receiving unit 22, and the detected down signal is processed in the optical receiving circuit 18. The output-intensity-saturation-type amplifying modulator 24 amplifies and attenuates a part of the branched down optical signal with the up signal from the drive unit 23, attenuates it, and modulates the up light signal. The modulated upstream optical signal is transmitted via the optical multiplexing / branching circuit 17 of the slave device and the optical fiber 15. The optical branching circuit 17 and the optical branching circuit 21 may be integrally formed.

Next, the operation in this configuration will be described. The operation of transmitting and receiving downstream optical signals is the same as in Fig. 2, and the operation of transmitting and receiving upstream optical signals is the same as in Fig. 3. The difference is that the provision of the optical coupling / branching circuits 14 and 17 in the master device and the slave device respectively enables bidirectional transmission with a single-core optical fiber. These optical couplers separate the upstream optical signal from the downstream optical signal. A directional optical coupling circuit, an optical circuit, or the like can be applied to the optical coupling / branching circuit. The optical transmission circuit and the optical reception circuit of the main device, and the optical transmission circuit and the optical reception circuit of the slave device operate in the same manner as in the first embodiment.

In a bidirectional optical transmission system in which direction-division multiplex bidirectional transmission is performed using a single optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber at the same wavelength. Therefore, when the main unit receives an upstream signal, it may interfere with a downstream signal reflected in the middle of the optical fiber. In the present embodiment, since the driving current of the light emitting element is controlled and the signal component is superimposed on the downstream signal, the spectrum width of the downstream signal light can be widened. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.

Therefore, the optical transmission circuit of the master device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the optical transmission circuit of the slave device is saturated. Amplification / attenuation circuit By using a configuration in which the upstream optical signal modulated by the upstream signal is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.

In addition, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as the downstream optical signal by using the output intensity-saturated amplifying modulator, even if the characteristics of the optical multiplexing / demultiplexing circuit have wavelength dependence, the upstream optical signal is transmitted. It is no longer necessary to control and maintain the signal wavelength with high precision.

Furthermore, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths in the optical transmission circuit of the slave device, the type of slave device is not different for each wavelength, but the same type of slave device is optional. The present invention can be applied to a slave device. In other words, interoperability (interoperability) between slave devices has become possible.

(Embodiment 3)

The present embodiment is a bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength multiplex multipoint transmission is performed between a main device and a plurality of slave devices. FIG. 5 shows the configuration of the embodiment of the present invention. In FIG. 5, 1 1 _ 1 to 1 1 1 N are the optical transmission circuit of the main unit, 1 2 — 1 to 1 2 — N are the optical reception circuit of the main unit, and 13 1 and 1 3 2 are the main units. 15-1 and 15-2 are optical fibers, 16-1 and 16-2 are wavelength-division multiplexing circuits provided in the middle of the optical fiber, and 18-8 :! 1 18 —N is the optical receiving circuit of the slave, and 19 _ 1 to 19 — N is the optical transmitting circuit of the slave. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11 1 1 to 11 1 N represent two or more optical transmission circuits. In FIG. 5, the downward arrow indicates the downward transmission direction, and the upward arrow indicates the upward transmission direction. The configuration of a system for performing bidirectional transmission between a main device and a plurality of slave devices will be described. In FIG. 5, a plurality of optical transmission circuits 11 1 to 11 N of the main unit are configured to superimpose a bias component on a signal component modulated by the downstream signal and to transmit each downstream optical signal to the wavelength multiplexing circuit 1 of the main unit. 3—Send to 1. Optical transmission circuit 1 1-1 to 1 1 1 N (Λ ₁ λ ₂ , ·, λ _Ν ). The wavelength division multiplexing circuit 13-1 converts the downstream optical signals of different wavelengths (λ 丄 ~! ^) Transmitted from the plurality of optical transmission circuits 111-1-11 to the optical fiber 15-1. Multiplex. The wavelength multiplexing circuit 16 _ 1 provided in the middle of the optical fino 15-1 separates the wavelength of each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 18-1 to 18-Ν of each slave device detect signal components from the downstream optical signal received through the optical fiber 15-1. The optical transmission circuit of each slave device 1 9 1:! 1-19 transmits an upstream optical signal, which is obtained by modulating a part of the received downstream optical signal with an upstream signal by a saturation amplification / attenuation circuit, to an optical fiber 15-2. Since the downstream optical signal is saturated and amplified by the output intensity saturated amplification modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as the downstream optical signal. The wavelength multiplexing circuit 16-2 provided in the middle of the optical fiber 15-2 is composed of a plurality of optical transmission circuits 1 9

1 to 19 — Wavelength multiplexes upstream optical signals of different wavelengths (AiAw) transmitted from Ν toward the main unit. The wavelength division multiplexing circuit 1 3-2 of the main unit is transmitted from the optical transmission circuit of multiple slave units 1 9-:! ~ 1 9-N

The upstream optical signals of different wavelengths (λ i to λ Ν) are transmitted for each wavelength to the optical receiver circuit 1 2 of the main unit. 1 1 2 — Separate the wavelength toward Ν. The plurality of optical receiver circuits 12-1 to 12-2 in the main unit detect upstream signals from the received upstream optical signals.

Next, the operation in this configuration will be described. The operation of transmitting and receiving downstream optical signals is the same as in Fig. 2, and the operation of transmitting and receiving upstream optical signals is the same as in Fig. 3. The difference is that the main unit has wavelength multiplexing circuits 13-1 and 13-2, and the wavelength multiplexing circuits 16-1 and 16-2 in the middle of the optical fiber. Thus, wavelength multiplexing multipoint transmission has become possible. The upstream optical signal and the downstream optical signal are multiplexed and demultiplexed by the wavelength multiplexing circuits 16-1 and 16-2. The optical transmission circuit and the optical reception circuit of the main device, and the optical transmission circuit and the optical reception circuit of the slave device operate in the same manner as in the first embodiment. Therefore, the optical transmission circuit of the master device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the optical transmission circuit of the slave device is saturated. By employing a configuration in which an upstream optical signal modulated by an upstream signal is transmitted by the amplification / attenuation circuit, the slave device can perform bidirectional transmission without using a light emitting element.

Also, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as the downstream optical signal by the output intensity saturated amplification modulator, the transmission circuit of the slave device on the wavelength characteristic of the wavelength multiplexing circuit It is no longer necessary to match or maintain the wavelength of the upstream optical signal with high precision.

Furthermore, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths in the optical transmission circuit of the slave device, the type of slave device is not different for each wavelength, but the same type of slave device is optional. The present invention can be applied to a slave device. In other words, interoperability (interoperability) can be secured between slave devices.

(Embodiment 4)

The present embodiment is a bidirectional optical transmission system in which a master device and a plurality of slave devices transmit one-core optical fiber in a direction multiplex bidirectional / wavelength multiplex multipoint transmission. FIG. 6 shows the configuration of the embodiment of the present invention. In Fig. 6, 1 1-1-: 1 1-N is the optical transmission circuit of the main unit, 1 2 _ 1-12 _ N is the optical receiving circuit of the main unit, 1 3-1, 1 3-2 is the main unit Wavelength multiplexing circuit of the device, 14 is an optical multiplexing / branching circuit of the main device, 15 is an optical fiber, 16 is a wavelength multiplexing circuit provided in the middle of the optical fiber, and 17-:! ~ 1 7 — N is the optical coupling / branching circuit of the slave device, 1 8 —:! 1 18 —N is the optical receiver circuit of the slave device, and 19 — 1 to 19 _N is the optical transmitter circuit of the slave device. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11-1 to 11_N represent two or more optical transmission circuits. In FIG. 6, the downward arrow indicates the downward direction, the upward arrow indicates the upward direction, and the up and down directions indicate the upward and downward bidirectional transmission directions. The configuration of a system for performing bidirectional transmission between a main device and a plurality of slave devices will be described. In FIG. 6, a plurality of optical transmission circuits 1 1 1 1 to 1 1 1 N of the main unit transmit each downstream optical signal obtained by superimposing a bias component on a signal component modulated by a downstream signal, to a wavelength multiplexing circuit 1 of the main unit. 3—Send to 1. Optical transmitter circuit 1 1 - 1 to 1 1 _ wavelength of the downstream optical signal of N is previously assigned _{_{(λ 1 λ 2, · ·}} λ Ν). The wavelength multiplexing circuit 13-1 of the main unit wavelength-multiplexes downstream optical signals of different wavelengths (ぇ to! ^) Transmitted from the plurality of optical transmission circuits 11-1 to 11_Ν. The optical combining / branching circuit 14 of the main device combines these downstream optical signals with the optical fiber 15_1. The wavelength multiplexing circuit 16 provided in the middle of the optical fiber 15 separates each downstream optical signal toward each slave device according to the wavelength. Optical coupling / branching circuit of each slave device 1 7 —:! 1 1 7 — Ν is an optical receiving circuit that supports downstream optical signals 1 8 —:! ~ 1 8 — branch to Ν. The optical receiver circuit 18-1 to 18-detects the signal component from the received downstream optical signal.

The optical transmission circuit of each slave device 1 9 1:! In 1910, a part of the received optical signal is branched by an optical branching circuit (not shown), and an upstream optical signal modulated by an upstream signal by a saturation amplification / attenuation circuit is transmitted. The optical branching circuit 17 for branching a part of the downstream optical signal and the optical combining / branching circuit 17 may be integrally configured. Since the downstream optical signal is saturated and amplified by the output intensity saturation amplification modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as the downstream optical signal. Optical coupling / branching circuit of slave device 1 7 —:! 1 1 7 — Ν joins the upstream optical signal to the optical fiber 15. The wavelength division multiplexing circuit 16 provided in the middle of the optical fiber 15 is composed of a plurality of optical transmission circuits 19 1:! 1 1 9 — Wavelength multiplexes upstream optical signals of different wavelengths (丄 to! ^) Transmitted from Ν toward the main unit. The wavelength multiplexing circuits 13 1 and 12 of the main unit transmit upstream optical signals of different wavelengths (λ _{;! To} λ _毎 ) transmitted from the optical transmission circuits 19 _ 1 to 19 In the main unit, the wavelength is separated toward the optical receiver circuit 12-1-1 2-—. Multiple of main units The optical receiving circuits 1 2-1 to 1 2 -N respectively detect upstream signals from the received upstream optical signals.

Next, the operation in this configuration will be described. The operation of transmitting and receiving downstream optical signals is the same as in Fig. 2, and the operation of transmitting and receiving upstream optical signals is the same as in Fig. 3. The difference is that the wavelength division multiplexing circuits 13 _ 1 and 13 _ 2 and the optical multiplexing / branching circuit 14 are provided in the main unit, the wavelength multiplexing circuit 16 is provided in the middle of the optical fiber, and the optical multiplexing and branching circuit 17 is provided in a plurality of slave units. — 2 to 17 — N means that single-core optical fiber direction multiplexing bidirectional and wavelength multiplexing multipoint transmission is possible between the main unit and multiple slave units. A plurality of upstream optical signals and a plurality of downstream optical signals are multiplexed or demultiplexed by these wavelength multiplexing circuits and optical multiplexing / branching circuits. Optical transmission circuit and optical reception circuit of main unit

, And the optical transmission circuit and the optical reception circuit of the slave device operate in the same manner as in the first embodiment.

In a bidirectional optical transmission system in which direction-division multiplex bidirectional / wavelength multiplex multipoint transmission is performed using a single optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber with the same wavelength. Therefore, when an upstream signal is received by the main unit, it may interfere with a downstream signal reflected in the middle of an optical fiber. In the present embodiment, the drive current of the light emitting element is controlled so that the signal component is superimposed on the downstream signal, so that the spectrum width of the downstream signal light can be increased. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.

Therefore, the optical transmission circuit of the master device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the optical transmission circuit of the slave device is saturated. By using a configuration in which the upstream optical signal modulated with the upstream signal by the amplification / attenuation circuit is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.

In addition, the optical transmission circuit of the slave device is output-saturation type amplification modulator. In order to transmit the upstream optical signal with the same wavelength as the downstream optical signal, the transmission circuit on the slave device side matches or maintains the wavelength of the upstream optical signal with high accuracy with respect to the wavelength characteristics of the wavelength multiplexing circuit. The need is gone.

(Embodiment 5)

The present embodiment is a bidirectional optical transmission system in which a single device and a plurality of slave devices perform single-core optical fiber direction multiplex bidirectional / wavelength multiplex multipoint transmission. FIG. 7 shows the configuration of the embodiment of the present invention. In FIG. 7, 1 1 1 to 1 1 —N is the optical transmission circuit of the main unit, 1 2 — 1 to 1 2 —N is the optical receiving circuit of the main unit, 13 is the wavelength multiplexing circuit of the main unit, 1 41 :! ~ 14 1 N is the optical branching circuit of the main unit, 15 is the optical fiber, 16 is the wavelength multiplexing circuit provided in the middle of the optical fiber, 1 7-:! ~ 1 7 — N is the optical coupling / branching circuit of the slave, 1 8 —:! .About.18-N is an optical receiving circuit of the slave device, and 19-11-1-19-N is an optical transmitting circuit of the slave device. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11_1 to 11-N represent two or more optical transmission circuits. In FIG. 7, the downward arrow indicates the downward direction, the upward arrow indicates the upward direction, and the up and down directions indicate the upward and downward bidirectional transmission directions.

The configuration and operation of a system for performing bidirectional transmission between a master device and a plurality of slave devices will be described. In FIG. 7, the difference from Embodiment 4 is the arrangement of the optical multiplexing / branching circuit and the wavelength multiplexing circuit of the main device. That is, the connection between the wavelength multiplexing circuit and the optical multiplexing / branching circuit of the main device is reversed from that of the fourth embodiment. Since the optical multiplexing / branching circuit and the wavelength multiplexing circuit are both linear circuits, the same operation is performed even if the order of connection is changed. Either Embodiment 4 or Embodiment 5 depending on the optical loss and required number of optical coupling / branching circuits and wavelength division multiplexing circuits Is selected.

In a bidirectional optical transmission system in which direction-division multiplex bidirectional / wavelength multiplex multipoint transmission is performed using a single optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber with the same wavelength. Therefore, when the main unit receives an upstream signal, it may interfere with a downstream signal reflected in the middle of the optical fiber. In the present embodiment, the drive current of the light emitting element is controlled so that the signal component is superimposed on the downstream signal, so that the spectrum width of the downstream signal light can be increased. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.

(Embodiment 6)

An optical transmission / reception device including an output intensity saturated amplification modulator will be described. An ordinary semiconductor optical amplifier performs optical amplification using a region where output light is linearly amplified with respect to input light. On the other hand, the output intensity saturated amplification modulator In the semiconductor optical amplifier, a region where the intensity of output light is saturated and amplified with respect to input light is positively used and modulation is performed. Since the output intensity-saturated modulator only amplifies the input light, the wavelength of the output light follows the input light.

Fig. 8 shows the schematic structure of the output intensity saturated amplification modulator. In FIG. 8, reference numeral 31 denotes an output intensity saturated amplification modulator, reference numeral 33 denotes an amplification modulation section, and reference numeral 34 denotes an emission port. 8, the input light is subjected to saturation amplification and attenuation by an input signal from a control terminal (not shown) in an amplification modulation section 33. The output light that has been amplified and modulated by the saturation amplification and attenuation is output from the output port 34. In this way, it is possible to modulate with the input signal by the saturation amplification and attenuation.

The degree of amplification as an amplifier is determined by the magnitude of the input signal current to the electrodes provided in the amplification modulation section. Increasing the input signal current increases the amplification. In addition, the saturation point at which the intensity of the output light is saturated with respect to the input light also increases at the same time. When the input signal current is reduced, the amplification degree of the input light is reduced or attenuated. When the optical phase is modulated by the input signal current, phase modulation is performed, or when the optical frequency is modulated, frequency modulation is performed. Here, the wavelength of the output light that has been subjected to saturation amplification and modulation is the same as the wavelength of the input light to the output intensity saturation type amplification modulator.

FIG. 9 shows a schematic structure of another output intensity saturated amplification modulator. The output intensity saturation amplification modulator described above performed saturation amplification and modulation with one electrode. This output intensity-saturated amplification modulator separates the saturation amplification section from the modulation section. Therefore, the control terminal is also separated into an amplification control terminal and a modulation input terminal.

In FIG. 9, reference numeral 32 denotes an output intensity saturated amplification modulator, reference numeral 35 denotes an amplification unit, reference numeral 36 denotes a modulation unit, and reference numeral 34 denotes an output port. In FIG. 9, for the input light, the amplification section 35 performs saturation amplification by a control input signal from an amplification control terminal (not shown), and the modulation section 36 performs modulation amplification on a modulation input terminal (not shown). Modulation is performed by these modulation input signals. The output light that has been amplified and modulated is output from the output port 34. In this way, by separating the amplifying section and the modulating section, the amplifying and modulating actions can be performed independently of each other. The amplification degree of the amplifier is controlled by the control input signal current to the electrodes provided in the amplifying section. Determined by the size. Increasing the control input signal current increases the amplification. In addition, the saturation point at which the intensity of the output light saturates the input light also increases. By dividing the amplifying unit into a plurality of parts and increasing the degree of amplification in the first stage and decreasing the degree of amplification in the second stage, saturation amplification can be performed efficiently. The modulation section amplifies or attenuates the output light by the modulation input signal current to modulate the intensity. Modulation input Modulation of the optical phase by the signal current results in phase modulation, or modulation of the optical frequency results in frequency modulation. Here, the wavelength of the output light that has been saturated amplified and modulated is the same as the wavelength of the input light to the output intensity saturated amplification modulator.

Therefore, if the output intensity saturated amplification modulator 31 or 32 is applied to the optical transceiver of the slave device described in the embodiment, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal. This eliminates the need to precisely control and maintain the wavelength of the upstream optical signal in the equipment.

(Embodiment 7)

An optical transmission / reception device including an output intensity saturated amplification modulator with a reflection film will be described. An ordinary semiconductor optical amplifier performs optical amplification using a region where output light is linearly amplified with respect to input light. Further, the optical signal incident from the entrance of the incident end face is amplified and emitted from the exit of the exit end face facing the incident end face. On the other hand, the output-intensity-saturation-type modulator with a reflection film is a semiconductor optical amplifier in which the region where the intensity of the output light saturates and amplifies with respect to the input light is positively used and modulation is performed. In addition, the end face facing the incident end face has higher reflection than the cleavage state. A reflection type configuration in which a film having a refractive index is coated, an optical signal incident from the entrance of the entrance end face is saturated and attenuated, attenuated, reflected by the coated reflective film, and transmitted from the entrance end face of the downstream optical signal. It is.

FIG. 10 shows a schematic cross section of an output intensity saturated amplification modulator with a reflection film. In FIG. 10, 33 is an amplification modulation section, 37 is an output intensity saturated amplification modulator with a reflection film, 39 is an input / output port, and 40 is a reflection film.

In FIG. 10, the amplification and modulation section 33 performs saturation amplification and attenuation on the incident light from the input / output port 39 by the input signal. The optical signal amplified and modulated by the saturation amplification and the attenuation is reflected by the reflection film 40 and emitted from the input / output port 39. The emitted optical signal saturates and attenuates the incident light, and its wavelength is the same as that of the incident light. The degree of amplification as an amplifier is determined by the magnitude of the input signal current to the electrodes provided in the amplification modulation section. Increasing the input signal current increases the amplification. Further, the saturation point at which the intensity of the output light is saturated with respect to the input light also increases at the same time. When the input signal current is reduced, the amplification degree of the input light is reduced or attenuated. When the optical phase is modulated by the input signal current, phase modulation is performed, or when the optical frequency is modulated, frequency modulation is performed.

Fig. 11 shows a schematic cross section of another output intensity-saturated amplification modulator with a reflection film. The output intensity saturation-type amplification modulator described above performed saturation amplification and modulation with one electrode. This output intensity-saturated amplification modulator is one in which the saturation amplification section and the modulation section are separated. Therefore, the control terminal is also separated into an amplification control terminal and a modulation input terminal. In FIG. 11, reference numeral 35 denotes an amplifying unit, 36 denotes a modulating unit, 38 denotes an output intensity saturation type amplifying modulator with a reflective film, 39 denotes an input / output port, and 40 denotes a reflective film.

In FIG. 11, the amplification section 35 performs saturation amplification on the incident light from the input / output port 39 by a control input signal from an amplification control terminal (not shown), and modulates the modulation input terminal by a modulation section 36. Modulation is performed using a modulation input signal from a (not shown). The optical signal amplified and modulated by the saturation amplification and attenuation is reflected by the reflection film 40 and emitted from the input / output port 39. Outgoing The wavelength of the optical signal is the same as that of the incident light because the incident light is saturated and amplified and attenuated.

The degree of amplification as an amplifier is determined by the magnitude of the control input signal current to the electrodes provided in the amplifier. Increasing the control input signal current increases the amplification. In addition, the saturation point at which the intensity of the output light saturates the input light also increases. By dividing the amplifying unit into a plurality of parts and increasing the degree of amplification in the first stage and decreasing the degree of amplification in the second stage, saturation amplification can be performed efficiently. The modulation section amplifies or attenuates the output light by the modulation input signal current to modulate the intensity. Modulation input Modulation of the optical phase by the signal current results in phase modulation, or modulation of the optical frequency results in frequency modulation.

Therefore, the output-intensity-saturation-type amplifying modulator 37 or 38 with the reflection film is connected to the optical transmitting / receiving device of the slave device, particularly, the same optical fiber for transmission of the downstream optical signal and transmission of the upstream optical signal described in the embodiment. When applied to the optical transceiver of the slave device used for the bidirectional optical transmission system to be used, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal, and the wavelength of the upstream optical signal in the slave device can be accurately determined. It is no longer necessary to control or maintain the same.

(Embodiment 8)

The present embodiment relates to an optical transmitting / receiving device including an output intensity saturated amplification modulator with a reflection film, and a bidirectional optical transmission system using the optical transmitting / receiving device. Fig. 12 shows the configuration of an optical transmitting and receiving device equipped with an output intensity saturation type amplification modulator with a reflection film. In FIG. 12, 15 is an optical fiber, 17 is an optical coupling / branching circuit of a slave device, 18 is an optical receiving circuit of a slave device, 19 is an optical transmitting circuit of a slave device, 22 is an optical receiving unit, and 23 is an optical receiving unit. The driving unit 37 is an output intensity saturated type amplification modulator with a reflection film.

In FIG. 12, a downstream optical signal transmitted through the optical fiber 15 is partially received by the optical multiplexing / branching circuit 17 and is received by the optical receiving unit of the optical receiving circuit 18. The other downstream optical signals branched by the optical coupler 17 are reflected. The light enters the output-saturation-amplified modulator 37 with a film, and is subjected to saturation amplification and modulation. The returned optical signal propagates through the optical fiber 15 as an upstream optical signal. The wavelength of the returned optical signal is the same as the wavelength of the downstream optical signal. Here, the same effect can be obtained by replacing the output intensity saturated amplification modulator 37 with a reflection film with the output intensity saturation amplification modulator 38 with a reflection film.

The output intensity saturated amplifier with reflection film has a common input port and output port, so that the same optical fiber is used for transmission of the downstream optical signal and transmission of the upstream optical signal described in the embodiment. Effective for optical transmission systems. When an output intensity saturated type amplifying modulator with a reflection film is applied to these transmission systems, it is clear from a comparison between FIG. 12 and FIG. 4 (b) that FIG. 12 shows the present embodiment. The optical branch circuit 21 of 4 (b) becomes unnecessary. For this reason, optical loss due to branching is also reduced.

Therefore, the output intensity saturated amplification modulator with the reflection film is used as a slave optical transmission / reception device, in particular, a bidirectional transmission using the same optical fiber for transmission of the downstream optical signal and transmission of the upstream optical signal described in the embodiment. When applied to the optical transceiver of the slave device used in the optical transmission system, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal, and the wavelength of the upstream optical signal in the slave device can be controlled with high precision. And maintenance was no longer necessary. Furthermore, in single-core optical fiber direction multiplex bidirectional transmission and single-core optical fiber bidirectional single-wavelength multiplex multipoint transmission systems, it was possible to reduce the number of optical branch circuits and reduce optical loss.

(Embodiment 9)

An optical transmission / reception device including an output intensity saturation amplification modulator having a saturation amplification unit and a modulation unit will be described. As the saturation amplifying unit, semiconductor optical amplification using a region where the intensity of the output light is saturated and amplified with respect to the input light is used. The modulator uses a semiconductor absorption type modulator that can be driven with a small and low voltage. Absorption type modulation enables high-speed modulation.

Fig. 13 shows the schematic structure of the output intensity saturated amplification modulator. Figure 13 Here, 61 is an output intensity saturation type modulator having a saturation amplification section and a modulation section, 62 is a saturation amplification section, 63 is a modulation section, 64 is a semiconductor active layer for realizing semiconductor optical amplification, and 65 is a semiconductor active layer. Is an absorption modulation layer for realizing modulation.

In FIG. 13, the input signal is subjected to saturation amplification of the input signal in the saturation amplifier 62, the bias component is amplified, the signal component is compressed, and the signal is modulated in the modulator 63. The modulator 63 realizes absorption type modulation and is not limited by the carrier lifetime of the active layer, so that high-speed modulation is possible. In this modulator, the modulation efficiency does not depend on the wavelength of the input light because the absorption edge is set to a shorter wavelength than the wavelength used. /

Therefore, when the output intensity saturated amplification modulator 61- is applied to the optical transceiver of the slave device described in the embodiment, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal. It was not necessary to control or maintain the wavelength of the upstream optical signal with high precision.

(Embodiment 10)

The present embodiment is a bi-directional optical transmission system in which a main unit and a plurality of slave units have two cores. FIG. 14 shows the configuration of the embodiment of the present invention. In Fig. 14, 25 is the optical transmission circuit of the main unit, 26 is the optical receiving circuit of the main unit, 15-1 and 15-2 are optical fibers, 16-1 and 16-2 are optical fibers Wavelength division multiplexing circuit provided in the middle of 1 18 —N is the optical receiving circuit of the slave, and 19 1 1 to 19 NN is the optical transmitting circuit of the slave. Here, the symbol N is used to represent two or more. For example, optical transmission circuit 1 1 1:! 1 1 1 —N represents two or more optical transmission circuits. In FIG. 14, the configuration of a system for performing bidirectional transmission between a main device and a plurality of slave devices, in which a downward arrow indicates a downward direction and an upward arrow indicates an upward transmission direction, will be described. In Fig. 14, the optical transmission circuit 25 of the main unit is modulated with a downstream signal. The respective downstream optical signals obtained by superimposing the bias components on the signal components thus transmitted are transmitted to the slave devices. At this time, in the optical transmission circuit 25 of the main device, any one of _N wavelengths (λ to λ _N ) is assigned to the wavelength of the wavelength variable light source included therein by an external control signal. The assigned wavelength is λ for the optical signal transmitted to the optical receiver circuit 18 — N of the slave device.

_波長 wavelength. That is, the optical transmission circuit 25 of the main device transmits an optical signal in a different time domain and wavelength for each slave device.

The wavelength multiplexing circuit 16-1 provided in the middle of the optical fiber 15-1 separates each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 18-1 to 18-Ν of each slave device detect a signal component from the downstream optical signal received through the optical fiber 15-1. The optical transmission circuit 19-1 to 19-の of each slave device transmits an upstream optical signal, which is obtained by modulating a part of the received downstream optical signal with an upstream signal by a saturation amplification / attenuation circuit, to an optical fiber 15-2. Send to. The wavelength to be transmitted is the same as that of the downstream optical signal because the downstream optical signal is saturated and amplified by the output intensity saturation type amplification modulator of the optical transmission circuit of the slave unit. The wavelength division multiplexing circuit 16-2 provided in the middle of the optical fiber 15-2 is a plurality of optical transmission circuits 19-1 :! 1 1 9 — Wavelength multiplexes upstream optical signals of different wavelengths (A i to A _N ) transmitted from Ν toward the main unit. The optical receiving circuit 26 of the main device detects an upstream signal from the received upstream optical signal.

Next, the operation in this configuration will be described. For transmission of the downlink signal, the time domain is separated for each signal transmitted to the reception circuit of the slave device. Furthermore, the wavelength of the tunable laser is changed for each signal transmitted to the receiving circuit of the slave device. For example, when transmitting to the receiving circuit 18-1 of the slave device, the downstream optical signal is transmitted with the wavelength λ and the time domain t. The operation of modulating the light with the downstream signal is the same as in Fig. 2. In the time domain, the receiving circuit of the slave device that receives data may be changed for each dime slot, or may be for each block in which information of a fixed length is collected. The time domain of the optical signal transmitted to the receiving circuit of a given slave device and the time domain of the optical signal transmitted to the receiving circuit of another slave device The interval of the time domain may be adjusted in advance according to the distance to a plurality of slave devices, or may be set at a fixed interval. The wavelength- and time-division multiplexed optical signal is separated for each slave device by a wavelength multiplexing circuit 16-1, and the optical receiver circuit 18 for the slave device 18 ::! ~ 18-received by N. Optical receiving circuit 1 8 1:! The receiving operation of the downlink signal at ~ 18-N is the same as that in Fig. 2 (d). Optical receiving circuit 18-1 to 18-N receives optical signals separated for each wavelength, in other words, for each time domain.

The transmission operation of the upstream signal is the same as the saturation amplification and modulation operation shown in FIG. 3, but the transmission optical signal transmits the upstream optical signal when the downstream optical signal reaches each slave device. The upstream optical signal from each slave device is multiplexed by the wavelength multiplexing circuit 16-2 and received by the optical receiving circuit 26 of the master device. The time domain interval is set when transmitting from the master device to the slave device so that the upstream optical signals from the slave devices do not overlap when receiving by the optical receiving circuit 26. The downstream optical signal and the upstream optical signal are transmitted using different optical fibers. By operating in this manner, two-core optical fiber bidirectional • wavelength time division multiplex multipoint transmission is performed.

In the main apparatus, instead of the optical receiving circuit 25, as shown in FIG. 5, a wavelength multiplexing circuit 13-2 of the main apparatus and optical receiving circuits 12-1 to 12_N of a plurality of main apparatuses are used. Is also good. With such a configuration, the time of the optical signal transmitted to the receiving circuit of a given slave device is determined so that the upstream optical signals from each slave device do not overlap regardless of the distance difference from the master device to each slave device. It is not necessary to set the interval between the region and the time region of the optical signal transmitted to the receiving circuit of another slave device.

Here, it is not necessary to assign all of A i A w to the wavelength assigned to each time domain, and it can be changed according to the amount of information transmitted to each slave device. Furthermore, the length of the time domain is not fixed for each slave device, but can be changed according to the amount of information transmitted to each slave device.

Therefore, the optical transmission circuit of the main unit covers the signal component modulated by the downlink signal. The downstream optical signal with the bias component superimposed is transmitted to the optical fiber, and the upstream optical signal obtained by modulating a part of the downstream optical signal received by the optical transmission circuit of the slave device with the upstream signal by the saturation amplification / attenuation circuit is output to the optical fiber. Thus, the slave device can perform bidirectional transmission without using a light emitting element.

In addition, the optical transmission circuit of the slave device transmits the upstream optical signal having the same wavelength as the downstream optical signal by the output intensity saturation type amplifying modulator, so that the wavelength of the upstream optical signal can be accurately determined with respect to the wavelength multiplexing circuit. You no longer need to control or maintain.

(Embodiment 11)

In the present embodiment, a single-core optical fiber bidirectional

• It is a bidirectional optical transmission system for wavelength time division multiplex multipoint transmission

. FIG. 15 shows the configuration of the embodiment of the present invention. In Fig. 15, 25 is the optical transmission circuit of the main unit, 26 is the optical receiving circuit of the main unit, 15-1, 15-2 is the optical finos, 16-1, and 16-2 are the optical The wavelength multiplexing circuit provided in the middle of the fiber, 18_1 to 18-0, is the optical receiving circuit of the slave device, and 19_1 to 19-N is the optical transmitting circuit of the slave device. Here, the symbol N is used to represent two or more. For example, the optical transmission circuit 11-1 to 1 l_N represents two or more optical transmission circuits. In FIG. 15, a configuration of a method of performing bidirectional transmission between a main device and a plurality of slave devices, in which a downward arrow indicates a downward transmission direction and an upward arrow indicates an upward transmission direction, will be described. In FIG. 15, the optical transmission circuit 25 of the main unit follows each downstream optical signal obtained by superimposing a bias component on a signal component modulated by the downstream signal. Send to device. At that time, in the optical transmission circuit 25 of the main device, the wavelength of the tunable light source included therein is controlled by an external control signal.

One of the N wavelengths (λ to λ _N ) is assigned. The wavelength to be allocated is such that the optical signal transmitted to the optical receiving circuit 18-N of the slave device has a wavelength of λΝ. That is, the optical transmission circuit 25 of the main device transmits an optical signal in a different time domain and wavelength for each slave device.

The wavelength multiplexing circuit 16 provided in the middle of the optical fiber 15 separates the wavelength of each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 18-1 to 18-Ν of each slave device detect a signal component from the downstream optical signal received through the optical fiber 15-1. The optical transmission circuit of each slave device 1 9 1:! 1 1 9 — Ν transmits the upstream optical signal, which is obtained by modulating a part of the received downstream optical signal with the upstream signal by the saturation amplification / attenuation circuit, to the optical fiber 15. Since the downstream optical signal is saturated and amplified by the output intensity saturation amplification modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as the downstream optical signal. The wavelength division multiplexing circuit 16 provided in the middle of the optical fiber 15 is composed of a plurality of optical transmission circuits 19 1:! ~ 19 19 Wavelength multiplexing of upstream optical signals of different wavelengths (~ ^) transmitted from the receiver to the main unit. The optical receiving circuit 26 of the main device detects an upstream signal from the received upstream optical signal.

Next, the operation in this configuration will be described. For transmission of the downlink signal, the time domain is separated for each signal transmitted to the reception circuit of the slave device. Furthermore, the wavelength of the tunable laser is changed for each signal transmitted to the receiving circuit of the slave device. For example, when transmitting to the receiving circuit 18-1 of the slave device, the downstream optical signal is transmitted at the wavelength λi and the time domain is t. The operation of modulating the light with the downstream signal is the same as in Fig. 2. In the time domain, the receiving circuit of the slave device for receiving may be changed for each time slot, or may be a block in which information of a fixed length is collected. The interval between the time domain of the optical signal transmitted to the reception circuit of a predetermined slave device and the time domain of the optical signal transmitted to the reception circuit of another slave device may be adjusted in advance in accordance with the distance to a plurality of slave devices. Alternatively, they may be spaced at regular intervals. The wavelength-time-division multiplexed optical signal is separated for each slave device by the wavelength multiplexing circuit 16 and received by the optical receiving circuits 18-1 to 18-N of the slave device. The receiving operation of the downlink signal in the optical receiving circuits 18-1 to 18-N is the same as that in FIG. Optical receiving circuit 18 — 1 to 18 — N receives optical signals separated by wavelength, in other words, by time domain.

The transmission operation of the upstream signal is the same as the saturation amplification and modulation operation shown in FIG. 3, but the transmission optical signal transmits the upstream optical signal when the downstream optical signal reaches each slave device. The upstream optical signal from each slave device is multiplexed by the wavelength multiplexing circuit 16 and received by the optical receiving circuit 26 of the master device. The time domain interval is set when transmitting from the master device to the slave device so that the upstream optical signals from the slave devices do not overlap when receiving by the optical receiving circuit 26. The downstream optical signal and the upstream optical signal are transmitted using the same optical fiber. By operating in this manner, single-core optical fiber bidirectional / wavelength time division multiplex multipoint transmission is performed.

In the main unit, instead of the optical receiving circuit 25, as shown in FIG. 6, a wavelength multiplexing circuit 13-2 of the main unit and optical receiving circuits 12_1 to 12-N of a plurality of main units are used. Is also good. With such a configuration, the time of the optical signal transmitted to the receiving circuit of a given slave device is determined so that the upstream optical signals from each slave device do not overlap regardless of the distance difference from the master device to each slave device. It is not necessary to set the interval between the region and the time region of the optical signal transmitted to the receiving circuit of another slave device.

Here, it is not necessary to assign all of the wavelengths λ ₁ to λ _} to the wavelengths assigned to each time domain, and they can be changed according to the amount of information transmitted to each slave device. Furthermore, the length of the time domain is not fixed for each slave device, but can be changed according to the amount of information transmitted to each slave device.

Therefore, the optical transmission circuit of the master device transmits the downstream optical signal in which the bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and transmits the signal to the slave device. A light-emitting element is used on the slave device side by transmitting the upstream optical signal, which is obtained by modulating a part of the downstream optical signal received by the optical transmission circuit with the upstream signal by the saturation amplification / attenuation circuit, to the optical fiber. Bidirectional transmission could be performed without the need for communication.

In addition, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as the downstream optical signal by the output intensity saturated amplification modulator, the wavelength of the upstream optical signal is transmitted to the wavelength multiplexing circuit / optical coupling / branching circuit. There is no longer any need to control or maintain high precision.

Claims

The scope of the claims

A bidirectional optical transmission system in which a two-core optical fiber is bidirectionally transmitted between a master device and a slave device using a first optical fiber and a second optical fiber,

The main device comprises: an optical transmission circuit for transmitting a downstream optical signal in which a bias component is superimposed on a signal component modulated by the downstream signal to the first optical fiber; and an upstream optical signal received through the second optical fiber. An optical receiving circuit that detects an upstream signal from a signal, the slave device detects an optical receiving circuit that detects the signal component from the downstream optical signal received through the first optical fiber, and the received downstream light A bidirectional optical transmission system comprising: an optical transmission circuit that transmits the upstream optical signal, which is obtained by modulating a part of a signal with the upstream signal by a saturation amplification / attenuation circuit, toward the second optical fiber. . A bidirectional optical transmission system in which a single-core optical fiber transmits a multiplexed bidirectional transmission between a master device and a slave device.

The main device comprises: an optical transmission circuit for transmitting a downstream optical signal in which a bias component is superimposed on a signal component modulated by the downstream signal toward the optical fiber; and an upstream signal received from the optical fiber to receive an upstream signal. And a light receiving circuit for detecting,

The slave device modulates a portion of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit, and an optical receiving circuit that detects the signal component from the downstream optical signal received through the optical fiber. An optical transmission circuit for transmitting the upstream optical signal toward the optical fiber. 3. The bidirectional optical transmission system according to claim 2, wherein the main device and the slave device are transmitted in a directionally multiplexed bidirectional manner using a single-core optical fiber. A sum amplifying / attenuating circuit, which is a semiconductor optical amplifier, wherein a film having a higher reflectivity than a cleavage state is coated on an end surface facing the incident end surface of the downstream optical signal, and a film is formed from the incident end surface of the downstream optical signal. A bidirectional optical transmission system characterized by a reflection type configuration for transmitting. A bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength multiplex multipoint transmission is performed between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber.

The main device comprises: a plurality of optical transmission circuits for transmitting, toward the first optical fiber, respective downstream optical signals in which a bias component is superimposed on a signal component modulated by a downstream signal; and the second optical fiber. A plurality of optical receiving circuits for detecting an upstream signal from each upstream optical signal received through the

The plurality of slave devices each include: an optical receiving circuit that detects the signal component from the downstream optical signal received through the first optical fiber; and each saturates a part of the received downstream optical signal. A bidirectional optical transmission system, comprising: an optical transmission circuit that transmits the upstream optical signal modulated by the amplification / attenuation circuit with the upstream signal toward the second optical fiber. A bidirectional optical transmission system in which a master device and a plurality of slave devices are transmitted in a direction-multiplexed bidirectional and wavelength-division multiplexed multipoint using a single optical fiber.

The main device comprises: a plurality of optical transmission circuits for transmitting, to the optical fiber, respective downstream optical signals in which a bias component is superimposed on a signal component modulated by a downstream signal; and each upstream light received through the optical fiber. A plurality of optical receiving circuits for detecting an upstream signal from the signal,

The plurality of slave units each receive through the optical fiber. An optical receiving circuit that detects the signal component from the downstream optical signal, and an optical receiver that modulates a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit. A bidirectional optical transmission system, comprising: an optical transmission circuit that transmits the signal to a fiber.

6. A bidirectional optical transmission system in which a master device and a plurality of slave devices according to claim 5 are transmitted in a directionally multiplexed bidirectional / wavelength multiplexed multipoint manner using a single-core optical fiber. An amplifier having a reflection type configuration in which a film having a higher reflectivity than a cleavage state is coated on an end face facing the incident end face of the downstream optical signal and transmitted from the incident end face of the downstream optical signal. A bidirectional optical transmission system characterized by the following. 7 A bidirectional optical transmission system in which a two-core optical fiber bidirectional and wavelength-division multiplexed multipoint transmission is performed between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber.

The master unit separates each downstream optical signal obtained by superimposing a bias component on a signal component modulated by a downstream signal into a wavelength and a time domain for each slave device, and transmits the separated optical signal toward the first optical fiber. Path, and at least one optical receiving circuit for detecting an upstream signal from each upstream optical signal received through the second optical fiber,

The plurality of slave devices each include: an optical receiving circuit that detects the signal component from the downstream optical signal received through the first optical fiber; and each saturates a part of the received downstream optical signal. A bidirectional optical transmission system, comprising: an optical transmission circuit that transmits the upstream optical signal modulated by the amplification / attenuation circuit with the upstream signal toward the second optical fiber. A two-way optical transmission system comprising a first optical fiber and a second optical fiber for bidirectional transmission of a two-core optical fiber and wavelength-division multiplexing multipoint transmission between the master device and a plurality of slave devices according to claim 7. A bidirectional optical transmission system, characterized in that a wavelength tunable light source capable of changing the wavelength of optical output to the wavelength of each slave device is used in the optical transmission circuit. A bidirectional optical transmission system in which a master device and a plurality of slave devices are multiplexed in one direction using a single optical fiber.

An optical transmission circuit that separates each downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal into a wavelength and a time domain for each slave device and transmits the separated optical signal toward the optical fiber; At least one optical receiving circuit for detecting an upstream signal from each upstream optical signal received through the optical fiber, wherein each of the plurality of slave devices is configured to detect the upstream signal from the downstream optical signal received through the optical fiber. An optical receiving circuit that detects a signal component; anda light that transmits the upstream optical signal, which is obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit, toward the optical fiber. A bidirectional optical transmission system comprising a transmission circuit. 10. The bidirectional optical transmission system according to claim 9, wherein the master device and the plurality of slave devices are transmitted in a single-core optical fiber in a direction multiplexed bidirectional / wavelength time division multiplexed multipoint transmission. An optical amplifier, wherein a coating having a higher reflectivity than the cleavage state is coated on an end face opposite to the incident end face of the downstream optical signal, and a reflection type light is transmitted from the incident end face of the downstream optical signal. A bidirectional optical transmission system characterized by having a configuration. 10. A bidirectional optical transmission system in which a master device and a plurality of slave devices according to claim 9 are directionally multiplexed bidirectionally and wavelength time division multiplexed multipoint transmitted by a single optical fiber. A bidirectional optical transmission system characterized by using a wavelength tunable light source whose length can be varied to the wavelength of each slave device. An optical transmitter / receiver having an optical transmission circuit for transmitting a second optical signal, which is obtained by modulating a part of the received first optical signal with a second transmission signal by a saturation amplification / attenuation circuit, toward an optical fiber, An optical transmission circuit for transmitting a first optical signal in which a bias component is superimposed on a signal component modulated by the first transmission signal;

An optical transmitting and receiving device comprising: an optical receiving circuit that detects a signal component from the second optical signal received through an optical fiber. An optical receiving circuit that receives an optical signal obtained by superimposing a bias component on a signal component modulated by a signal through an optical fiber; and an optical fiber that modulates a part of the received optical signal with a signal that is transmitted by a saturation amplification / attenuation circuit. An optical transmitting and receiving device comprising: an optical transmitting circuit that transmits the signal to the optical transmitter. 13. The optical transceiver according to claim 12, wherein the bias component is at least 50%, preferably at least 100% of the signal component. 14. The optical transmitting and receiving apparatus according to claim 13, wherein the saturation amplification / attenuation circuit is a semiconductor optical amplifier including: an amplification unit that controls an amplification degree by a control current; and a modulation unit that modulates an optical signal by a signal to be transmitted. An optical transmission / reception device characterized by the above-mentioned. 14. The optical transmitting and receiving device according to claim 13, wherein the saturation amplification / attenuation circuit is a semiconductor optical device having an amplification unit that saturates by a control current and a modulation unit that absorbs an optical signal by a signal to be transmitted. An optical transceiver.