| 摘要 |
PURPOSE:To attain effective relay transmission by allowing an optical repeater to supplement a dummy signal and to send the result when an optical signal is in non- signal state on a transmission line in the relay transmission system of the optical signal. CONSTITUTION:An optical repeater 11 is provided with an optical signal detection signal detection circuit 4, a dummy signal generating circuit 3 and a signal changeover device 5 in addition to an optical receiver 1, a 3R circuit 2 and an optical transmitter 6. The signal changeover device 5 has a function of selectively switching an input to the optical transmitter 6 to an output of the 3R circuit 2 and the dummy signal generating circuit 3 and controlled by the optical signal detection circuit 4. The optical signal detection circuit 4 detects the presence of the optical signal inputted to the optical receiver 1 and outputs a control signal to the signal changeover device 5 so that the signal changeover device 5 is thrown to the position of the 3R circuit 2 when the optical signal is inputted and the signal changeover device 5 is thrown to the position of the dummy signal generating circuit 3 when the optical signal is not inputted. Thus, effective countermeasure such as complete extinct state of the output is attained and a system fault due to interruption of the optical signal is prevented. |
