| 摘要 |
PURPOSE:To improve the S/N in the reception of a monitor reply signal at a terminal station by sending the monitor reply signal to a transmission line directed by a control instruction from the terminal station via a monitor reply signal exclusive 2-way reproduction section. CONSTITUTION:A reply signal as a result of the monitor activity is led to a monitor reproduction repeater circuit unit 21 independent of a unit for communication via a modulation circuit 17, modulation is applied to a signal received via a monitor reply signal exclusive optical fiber transmission line 10 to generate a monitor reply signal. A control instruction signal being a direction command sent from a terminal station representing the transmission direction of the monitor reply signal is received by a communication reproduction repeater circuit unit 14a, demodulated by a demodulation circuit 15 and sent to a switch control circuit 23. The switch control circuit controls optical signal switches 22a, 22b in response to an instruction signal to form a monitor signal reply channel in matching with the instruction signal via optical demultiplexer/ multiplexers 24a, 24b. Thus, the S/N of the monitor reply signal at the reception side of terminal station is improved. |
