| 摘要 |
PURPOSE:To enable to transmit the monitor-sessional signal without increasing the band of transmission line, by the pulse width modulation of monitoring and sessional signal, and transmitting it to the communication digital signal with superposition. CONSTITUTION:In the superposition circuit 3, the input digital signal (a) and the monitor-sessional signal (b) in pulse width modulation are outputted with superposition. The superposition signal (d) is inputted to the drive circuit 7 to emit the light emitting element 8 and it is transmitted with the transmission line 9 by optical fiber. The light is received with the photo detector 10, and the digital signal (a) is picked up from the superposition signal (d) after amplification, the content of the information is identified at the indentifying circuit 13 and the monitor and sessional signal (b') is demodulated with the low pass filter 15. Thus, without producing the interference between codes of digital signal for communication, the transmission of the monitoring and sessional signal can be transmitted. |
