| 摘要 |
PURPOSE:To realize detection for a fault of a connection box or an optical fiber of the front stage in an optical cable transmission system, by sending back the signals of different frequencies of oscillation by a connection box and an optical repeater that detected a fault and via a metallic conductor. CONSTITUTION:When the code rule of the input signal is disturbed, a code rule monitoring circuit 30 monitoring the code rule under transmission produces the pulse to oscillate a proper signal of oscillating frequency fn+2 for each optical repeater 4'. This signal is sent back to a transmission end office 1' via an intermediate paired metallic conductors 14. Thus a faulty repeater can be decided at the office 1'. In case an optical fiber cable 13 is broken, the frequency fn+1 is oscillated at every repeater 4' by a large change of the voltage to be supplied to a photoelectric converting circuit 22 in an AGC circuit 27 and then sent back to the office 1' via the conductors 14. As a result, the office 1' can decide a fault of the cable 13 at the front stage of the repeater 4'. |
