Breaking through the bandwidth barrier in distributed fiber vibration sensing by sub-Nyquist randomized sampling

The round trip time of the light pulse limits the maximum detectable frequency response range of vibration in phasesensitive optical time domain reflectometry (phi-OTDR). We propose a method to break the frequency response range restriction of phi-OTDR system by modulating the light pulse interval randomly which enables a random sampling for every vibration point in a long sensing fiber. This sub-Nyquist randomized sampling method is suits for detecting sparsewideband- frequency vibration signals. Up to MHz resonance vibration signal with over dozens of frequency components and 1.153MHz single frequency vibration signal are clearly identified for a sensing range of 9.6km with 10kHz maximum sampling rate.