Interference-fading-free phase-demodulated OTDR system

Abstract

A phase-shifted double pulse method is proposed to reduce the influence of inner-pulse interference induced fading on phase demodulation of the Φ-OTDR. The feasibility of the technique is experimentally verified and the measurement resolution of the Φ-OTDR is minimized to as low as 0.1rad by using this technique. The experimental system demonstrates a distributed phase monitoring capability over 4km range with SNR of >20 and detection bandwidth of >360Hz.