| 摘要 |
PURPOSE: To form a main signal system and a MODEM circuit for auxiliary signals independently of each other by multiplexing the optical signal which is modulated by an auxiliary signal having a satisfactorily low transmission speed to another optical signal which is modulated by the main digital signal and transmitting those multiplexed signals. CONSTITUTION:A main digital signal 101 undergoes code conversion via a main signal optical transmitter 11 and is converted into an optical signal after elimination of the low frequency component. This optical signal is sent to a multiplexer 13. While an auxiliary digital signal 102 of a low speed is converted into an optical signal by an auxiliary signal optical transmitter 12 and outputted to the multiplexer 13. These optical signals multiplexed by the multiplexer 13 are sent to the receiver side. At the receiver side, a demultiplexer 14 branches the received optical signals in a proper ratio and converts them into electric signals via a main signal optical transmitter 15 and an auxiliary signal optical receiver 16 with operations adverse to those carried out at the transmitter side. |
