JPH04223727A - Light transmitter-receiver - Google Patents

Abstract

PURPOSE:To set the reception levels of light signals to be constant in the signals of respective slave devices by providing light signal level control circuits and outputting a light signal level which is in inverse proportion to received optical power. CONSTITUTION:The light signal level which is light-emitted from a center device is transmitted to the respective slave devices. At that time, the light signal levels which the light-receiving elements 7 of receivers 13 in the light transmitter-receivers 12 in the slave devices differ by the loss of a transmission line. Thus, the light signal level control circuits 10 of the transmitter in respective slave devices set the light signal levels which are in inverse proportion to the light signal level detected in the light signal level detection circuit 9 of the receiver 13 and transmit the light signal. Since the circuits 10 control the setting of the light signal level, the light signal levels from the respective slave devices, which the center device 5 light-receives, become constant in respective slave devices and the destruction of the light-emitting element 7 is prevented.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This field relates to one-to-many bidirectional optical communication.

0002

[Prior Art] Published Patent Publication (A) Hei 1-502470
As shown in Figure 2, in order to keep the optical power from each child device constant at the central device, the central device measures the optical power from each child device, multiplexes that information with the signal of the opposing device, and sends the information to the child device. The child device then controlled the optical output power based on the information.

0003

[Problems to be Solved by the Invention] In the above conventional technology, the central device measures the optical power of each child device, converts the measured value into A/D, and the child device converts the signal from the central device into a D/A converter. There is a problem that it is necessary to perform conversion and control, making the circuit and control sequence complicated.

An object of the present invention is to easily and inexpensively control the optical transmission power of slave devices (without being controlled by a central device).

[0005]

[Means for Solving the Problems] The above object is to detect the received optical signal level at the receiver of the slave device, and send to the transmitter an optical signal with a level inversely proportional to the optical signal level detected at the receiver. This is achieved by

[0006]

[Operation] In general, in single-fiber two-way communication, the transmission loss for uplink and downlink is almost equal, so information about the level of the optical signal received by the receiver of the child device equipped with a transmitter/receiver is detected, and the detected optical signal is By controlling the optical signal to be sent out at a level inversely proportional to the level, the level of the received light signal from each child device received by the central device remains constant even if there is a difference in the distance between the central device and each child device. You can keep it. Since only the slave devices are controlled without being controlled by the central device, the optical transmission power of the slave devices can be controlled easily and inexpensively.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the optical transceiver 15. The optical transceiver 15 is composed of a receiver 13 and a transmitter 14. The receiver 13 includes a light receiving element 7, a decoding circuit 8 for decoding an optical signal, and an optical signal level detection circuit 9 for detecting the level of the received light signal. The optical signal entering the optical coupler/splitter 6 is received by the light receiving element 7 of the receiver 13, and the level of the received light signal of the light receiving element 7 can be detected by the optical signal level detection circuit 9. The transmitter 14 includes an optical signal level control circuit 10, a drive circuit 11, and a light emitting element 12. The optical signal level control circuit 10 sets an optical transmission signal level that is inversely proportional to the optical signal level detected by the optical signal level detection circuit 9 of the receiver 15. The set optical transmission signal level is then output to the drive circuit 11, and the light emitting element 12 emits light.

FIGS. 2 and 3 show the configuration of an optical communication system to which the optical transceiver 15 described in FIG. 1 is applied. Figure 2, Figure 3
The level of the optical signal emitted from the central device 5 in is transmitted to each child device 4a to 4n, but the level of the light signal received by the light receiving element 7 of the receiver 13 of the optical transceiver 12 of each child device 4a to 4n is as follows. Since the transmission path loss to each child device 4a to 4n is different, it differs depending on each child device 4a to 4n. The optical signal level control circuit 10 of the transmitter 14 of each child device 4a to 4n sets an optical signal level inversely proportional to the optical signal level detected by the optical signal level detection circuit 9 of the receiver 14, and transmits the optical signal. . Each child device 4a to 4n receives light at the central device 5 by performing the above control.
The level of the optical signal from is constant among the child devices 4a to 4n.

The above operation is shown in FIG. Figure 5 (1) is
The respective light reception signal levels 17a to 17n received by the child devices 4a to 4n are shown. Transmitter 1 of each child device 4a to 4n
The optical signal level control circuit 10 of No. 4 sets and transmits optical transmission signal levels 18a to 18n that are inversely proportional to the respective received light signal levels 17a to 17n. The optical transmission signal levels 18a to 18n sent out by the transmitter 10 are shown in FIG.
2). FIG. 5(3) shows the light reception signal level 19 from each child device 4a to 4n that is received by the central device 5.
a to 19n are shown. By setting and transmitting optical transmission signal levels 18a to 18n that are inversely proportional to the light reception signal levels 17a to 17n received by each of the child devices 4a to 4n, the light from each of the child devices 4a to 4n received by the central device 5 is reduced. The light reception signal levels 19a to 19n are constant among the optical signals of each child device 4a to 4n.

FIG. 4 shows the optical transceiver 1 described in FIG.
5 shows the configuration of an optical transceiver equipped with an optical output limiting circuit 16 to prevent the transmitter 14 of the optical transceiver 15 from emitting excessive light and destroying the light emitting element 12. The optical signal entering the optical coupler/splitter 6 is received by the light receiving element 7. The light reception signal level at the light emitting element 7 is detected by the optical signal level detection circuit 9. When the level detected by the optical signal level detection circuit 9 falls below a certain level, the optical output limiting circuit 16 of the transmitter 14 limits the optical transmission level set in the optical signal level control circuit 10, To prevent the light emitting element 7 from being destroyed by causing the light emitting element 7 to emit excessive light.

FIG. 6 shows the configuration of an optical transceiver having a function of completely stopping the optical transmission signal when the received signal cannot be received normally. The optical signal received by the light receiving element 7 in FIG. 6 is converted into an electrical signal by a decoding circuit 8, and a monitoring circuit 20 monitors the error rate such as frame synchronization. When the monitoring circuit 20 detects an abnormality in the received signal, it notifies the optical output limiting circuit 16 of the abnormality,
The optical transmission signal will be completely stopped. When one of the child devices 4a to 4n of the optical communication system shown in FIGS. 2 and 3 cannot receive a received signal normally, the optical transmission signal is completely stopped, and an abnormal signal is sent out. prevent interference with optical signals sent by child devices.

[0013]

Effects of the Invention By performing optical transmission power control in the slave devices 4a to 4n in the embodiment, even if the transmission path loss between the central device 5 and each slave device is different, the slave devices 4a to 4n
The optical signal level at which the central device 5 receives the optical signal emitted from the transmitter 11 of n can be made constant among the child devices. In addition, even if the light receiving power of the slave device becomes abnormally small or an error is detected in the light receiving signal, the provision of the light output limiting circuit 16 prevents the light emitting device from being emitted with excessive light and destroying the light emitting element. It is possible to prevent the signal from being transmitted and interfering with the upstream signals of other child devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical transmission power control method in a child device according to the present invention.

FIG. 2 shows a schematic configuration diagram of an optical communication system targeted by the present invention.

FIG. 3 shows a schematic diagram of an optical communication system targeted by the present invention.

FIG. 4 shows a method for limiting optical transmission power in a child device according to the present invention.

FIG. 5 shows optical transmission and reception signal levels in an optical communication system targeted by the present invention.

FIG. 6 shows a method for stopping optical transmission power in a slave device according to the present invention.

[Explanation of symbols] 1...Transmission line 1, 2...Transmission line 2, 3, 3a, 3b, ~3n
...Passive optical splitter, 4a, 4b to 4n... Child device, 5... Central device, 6... Optical coupler/splitter, 7... Light receiving element, 8... Decoding circuit, 9... Optical signal level detection circuit, 10... Optical signal Level control circuit, 11... Drive circuit, 12... Light emitting element, 13... Receiver, 14... Transmitter, 15... Optical transceiver, 16... Optical output limiting circuit, 17a to 17n... Light reception signal level of each child device, 1
8a-18n...Each child device optical transmission signal level, 19a-1
9n...Central unit light reception signal level, 20...Monitoring circuit.

Claims (5)

[Claims] Claim 1: In an optical transceiver capable of single-fiber bidirectional transmission, which includes an optical transmitter and an optical receiver in the same device, the optical signal level is controlled so as to output an optical signal level inversely proportional to the received optical power. Featured optical transceiver. [Claim 2] Transmission line 1 connecting the central device and the optical passive splitter.
In a single-fiber bidirectional optical transmission network consisting of a transmission line 2 connecting a passive optical splitter and multiple slave devices, the purpose is to make the optical signal level from each slave device constant at the optical receiver of the central device. The optical transceiver according to claim 1. 3. In a bus-type single-fiber bidirectional optical transmission network comprising a transmission line 1 having a central unit and a plurality of passive optical splitters, and a transmission line 2 connecting the optical passive splitter and child devices, the central unit 2. The optical transceiver according to claim 1, wherein the optical signal level from each child device in the optical receiver is made constant. 4. The optical transceiver according to claim 1, further comprising an optical output limiting circuit to prevent the transmitter from emitting excessive light and destroying the light emitting element when the received optical power falls below a certain level. 5. The optical transceiver according to claim 1, further comprising a function of completely stopping the upstream optical signal when the received signal cannot be received normally.