Ultra long single span distributed sensing distance over 200km based on the phase-sensitive OTDR with bidirectional high-order Raman amplification

An ultra-long phase-sensitive optical time domain reflectometry(Φ -OTDR) that can achieve sensing distance 205.46km single fiber with spatial resolution of 15m is presented to solve the problem of long-distance fiber optic cable monitoring, which use dual-coherent optic source and bidirectional high-order Raman amplification. To the best of our knowledge, this is the record sensing distance using a commercial Raman-line Φ -OTDR system.