JPH08274719A - Optical output control circuit of optical communication system - Google Patents

Abstract

PURPOSE: To provide the optical output control circuit of a transmitter which can control the photodetection level when a master station photodetects signals sent by respective slave stations to a constant value. CONSTITUTION: A slave station receives an optical signal from the master station by a PD 201 and detects its reception level, compares the reception level with the previously set transmission level of the master station by an output control circuit 300 to calculate the loss of the optical transmission line, and adds the loss to the previously set reception level of the master station, thereby outputting an optical output control signal. This optical output control signal is outputted to an LD drive circuit 102 to control the optical output level of an LD 103 for transmission from the slave station to the master station. Through this control, the loss of the optical transmission line between the master station and slave station is canceled and even when the distances of transmission lines between the master station and plural slave stations are different, the master station can perform reception with the constant level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission circuit used in a passive double star optical communication system (hereinafter referred to as PDS optical communication system) and the like, and more particularly to a control circuit for controlling an optical transmission output. .

[0002]

2. Description of the Related Art FIG. 4 shows the configuration of an optical transmitter used in a conventional PDS optical communication system. Buffer circuit 401
Receives the clock C1 and the data D1 as input, and generates the waveform-shaped transmission data D2. The LD drive circuit 402 receives the transmission data D2 and the LD output control signal D4 as input, and generates an LD drive signal D3 for driving the laser diode (LD). The LD 403 receives the LD drive signal D3 as an input and generates an optical transmission signal S1. At that time, a part of the optical signal S1 is detected by the photodiode (PD) 404, and a part of the optical signal is current-converted to generate an optical transmission signal monitor current I2. The optical output automatic control (APC) 405 receives the optical transmission signal monitor current I2 as an input and generates the above-mentioned LD output control signal D4 for controlling the LD bias with a signal obtained by current-current conversion to keep the optical output constant. To do.

[0003]

The optical transmitter having such a structure is effective in keeping the optical output in each of them constant, but a plurality of terminal stations that constitute the PDS optical communication system use this transmitter. , When used for multiple slave stations,
In the master station, since the distances of the optical transmission lines from the plurality of slave stations connected by the optical transmission line are different from each other, the loss in the optical transmission line is also different. The optical receiver is required to support various light levels from each slave station. In particular, in the case of optical burst signal transmission, the master station needs to respond to the optical burst signal at high speed, but it is necessary to secure a wide dynamic range and realize a high-speed automatic output amplitude control (AGC) circuit at the same time. Was technically difficult.

Further, when the optical output level at the slave station is fixed to a constant value as described above, the distance from the master station is short and the light receiving level at the optical receiver of the master station is the maximum allowable light receiving level. If it exceeds the limit, it is necessary to reduce the optical transmission level of the slave station, and for this reason, the configuration is complicated, such as mounting an optical attenuator on the slave station, and complicated adjustment work is required. Problem arises.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical output control circuit in a transmitter capable of controlling a light receiving level when a signal transmitted from each child station is received in a parent station. It is in.

[0006]

According to the optical output control circuit of the present invention, the slave station is preset with the means for receiving the optical signal from the master station and detecting the reception level of the optical signal. Means for calculating the loss in the optical transmission line by comparing with the transmission level of the master station, and adding this loss to the preset reception level of the master station to output an optical output control signal, and from the slave station Means for transmitting an optical signal to the master station and controlling the optical transmission level thereof by the optical output control means.

For example, the slave station receives a photodiode that outputs a received light current according to the received optical signal from the parent station, an I / V conversion circuit that converts the received light current into a received light voltage, and the received light voltage. , Calculate the transmission line loss voltage in the optical transmission line by comparing this with the voltage value obtained by converting the preset optical transmission level of the master station into a voltage value, and use this transmission line loss voltage in the optical reception level at the opposite station. Output control circuit that outputs a light output control signal in addition to the received light level voltage that is converted into a voltage, a laser diode drive circuit that inputs this light output control signal and outputs a corresponding laser diode drive current, and this laser A laser diode is provided which inputs a diode drive current and outputs an optical output signal corresponding to the optical output control signal.

[0008]

The slave station receives the optical signal from the master station and compares it with the output level of the master station to calculate the loss in the optical transmission line. Then, by transmitting an optical signal with an output obtained by adding this loss amount to the reception level of the master station, the loss of the optical transmission line between the master station and the slave station is offset, and the master station and multiple slave stations are Even if the distances of the optical transmission paths between the two are different, the master station can receive at a constant level.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a PDS optical communication system to which the present invention is applied. One master station 1 and N (N is an integer of 1 or more) slave stations 21 to 2N are optical star couplers as optical transmission lines. 3, a 1: N configuration is adopted, and the master station 1 and the N slave stations 21 to 2N mutually perform signal transmission by optical burst signals. Therefore, the master station and each slave station are provided with an optical receiver and an optical transmitter, respectively.

FIG. 2 is a block diagram showing the configuration of the optical transmitter 100 and the optical receiver 200 provided in each slave station 21-2N. The optical transmitter 100 inputs the input clock C1 and data D1 into the buffer circuit 101, and the communication data D
Generates 2. Then, this communication data D2 is input to the LD drive circuit 102 to generate an LD drive current IS as an LD drive signal, and the LD 103 is driven by this LD drive current IS to output the optical output signal S1 to the optical transmission line 3. To send. Further, the optical receiver 200 receives the optical signal S2 transmitted from the optical transmission line 3 at the PD 201 and receives the received current I1.
Is converted into a reception voltage V1 in the I / V conversion circuit 202. Then, the buffer circuit 203 is configured to output the reception data D5 from the reception voltage V1.

An output control circuit 300 is inserted between the output side of the I / V conversion circuit 202 of the optical receiver 200 and the LD drive circuit 102 of the optical transmitter 100, and
The LD drive circuit 102 is controlled based on the received light voltage V1 output from the / V conversion circuit 202 and the preset master station transmission level voltage V2, and the LD drive current IS that is the output thereof is controlled. Composed. Here, the output control circuit 300 calculates the transmission line loss voltage V3 (= V2-V1) in the optical transmission line by taking the difference between the received light voltage V1 and the master station transmission level voltage V2. Furthermore, the output control circuit 300 uses the preset light reception level voltage VA at the master station and the obtained transmission line loss voltage V3,
The light output control signal VS (= VA + V3) is calculated, and this light output control signal VS is output to the LD drive circuit 102.

Next, the operation of the optical transmitter and the optical receiver having the above configurations will be described. In the optical receiver 200, PD2
01 receives the optical signal S1 as an input and outputs a light receiving current I1 corresponding to the optical level of the optical signal S1. The I / V conversion circuit 202 receives the received light current I1 as an input and converts the voltage into a received light voltage V1 corresponding to the received light current I1.
Is output. The buffer circuit 203 receives the received light voltage V1 and outputs the received data D5.

The received voltage V1 is output to the output control circuit 3
It is also input to 00. In the output control circuit 300, as shown in the flow chart of FIG. 3, information of the master station transmission level voltage V2 obtained by converting the optical transmission level of the master station 1 into voltage is set in advance. By comparing V1 with each other, the transmission line loss voltage V3 = V2-V1 corresponding to the loss of the optical transmission line between the master station 1 and the own station is calculated. Further, the light reception levels from the respective slave stations 21 to 2N in the master station 1 are converted into a voltage and set as the light reception level voltage VA, and the light reception level voltage VA of the receiver of the master station corresponds to the transmission line loss. The optical output control signal VS (= VA + V3) added with the transmission line loss voltage V3 is output.

Therefore, the LD drive circuit 102 receives the optical output control signal VS from the output control circuit 300,
The LD drive current IS corresponding to VS is output. LD10
The LD drive current IS is input to the optical fiber 3 and outputs an optical output signal S1 with an optical output corresponding to the LD drive current IS. This optical output signal S1 is an output to which only the loss voltage V3 is added in advance, even when the optical transmission line 3 receives a loss corresponding to the loss voltage V3 when transmitted to the master station 1. When it is received by the optical receiver of the master station 1, it is in a state of being attenuated by the transmission loss voltage V3, and in the optical receiver of the master station, the set light reception level voltage VA is set.
It is possible to receive light.

As a result, when the distances of the optical transmission lines between the master station and the N slave stations are different, the loss voltage V3 in the optical transmission lines between the slave stations and the master station is different. As a result, each slave station has different output levels corresponding to the loss voltage V3. Therefore, the master station can receive the optical signal transmitted from each individual station at a constant light reception level, and the master station can respond to the optical burst signal at high speed even in the case of optical burst signal transmission. Therefore, the dynamic range can be narrowed, which makes it possible to realize a high-speed AGC circuit.

Further, when the optical transmission path between the master station and the slave station is short, the optical transmission level of the slave station is reduced, so that the light receiving level of the optical receiver of the master station exceeds the maximum allowable light receiving level. Of course, the work of mounting the optical attenuator on the slave station and adjusting the amount of attenuation becomes unnecessary.

[0017]

As described above, in the optical output control circuit according to the present invention, the slave station receives the optical signal from the master station and detects its reception level, and the detected reception level in advance. A means for calculating the loss in the optical transmission line by comparing with the set transmission level of the master station, and adding this loss to the preset reception level of the master station, and outputting an optical output control signal, And a means for transmitting an optical signal from the slave station to the master station according to the transmission level controlled by the optical output control means, so that the optical reception level of the optical signal from each slave station in the optical receiver of the master station Can be made constant, the dynamic range of the master station optical receiver can be narrowed, and the high-speed AGC circuit can be easily designed. Further, since the optical output is automatically controlled, it is not necessary to attach an optical attenuator when installing the slave station.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a PDS optical communication system to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of an optical output control circuit of a slave station.

FIG. 3 is a flowchart for explaining the operation of the output control circuit.

FIG. 4 is a block diagram showing a configuration of a conventional light output control circuit.

[Explanation of symbols]

 1 Master Station 21 to 2N Slave Station 3 Optical Star Coupler (Transmission Line) 100 Optical Transmitter 101 Buffer Circuit 102 LD Drive Circuit 103 LD (Laser Diode) 200 Optical Receiver 201 PD (Photodiode) 202 I / V Conversion Circuit 203 Buffer circuit 300 Output control circuit

Claims (3)

[Claims] 1. An optical communication system for performing optical signal communication between a master station and a plurality of slave stations, wherein the slave station receives an optical signal from the master station and detects its reception level. And, the loss in the optical transmission path is calculated by comparing the detected reception level with the preset transmission level of the master station,
And a means for outputting an optical output control signal by adding this loss to the preset reception level of the master station, and transmitting an optical signal from the slave station to the master station, and the optical transmission level of which is the optical output. An optical output control circuit in an optical communication system, comprising: a unit controlled by a control unit. 2. The slave station receives a photodiode that outputs a received light current according to the received optical signal from the parent station, an I / V conversion circuit that converts the received light current into a received light voltage, and the received light voltage. , Calculate the transmission line loss voltage in the optical transmission line by comparing this with the voltage value obtained by converting the preset optical transmission level of the master station into a voltage value, and use this transmission line loss voltage in the optical reception level at the opposite station. Output control circuit that outputs a light output control signal in addition to the received light level voltage that is converted into a voltage, a laser diode drive circuit that inputs this light output control signal and outputs a corresponding laser diode drive current, and this laser 2. An optical output control circuit in an optical communication system according to claim 1, further comprising a laser diode which inputs a diode drive current and outputs an optical output signal corresponding to the optical output control signal. 3. The slave station includes an optical receiver that receives an optical signal from the master station and outputs a received signal, and an optical transmitter that transmits the transmission signal as an optical signal toward the master station, Output control inserted between the photodiode and I / V conversion circuit of the optical receiver, the laser diode drive circuit and laser diode of the optical transmitter, and the I / V conversion circuit and laser diode drive circuit And a circuit.
Output control circuit in the optical communication system of the above.