Fault location for optical transmission line by signal multiplexing method

Two signal multiplexing schemes have been proposed and experimentally demonstrated in optical time domain reflectometry (OTDR) for fault location of fibre optical transmission line to obtain high measurement efficiency. The backscattered Rayleigh light of the multiplexing probe signals is transferred to corresponding heterodyne intermediate frequency (IF) through heterodyning with single frequency local oscillator (LO). Then the detected signals are demultiplexed and finally extracted by digital signal processing method. Experimental results show that by use of the multiplexing method, the measurement efficiency of OTDR can be enhanced by nearly 16 times.