All-fiber monostatic pulsed laser Doppler vibrometer: A digital signal processing method to eliminate cochannel interference

Abstract

A 1.55 μm all-fiber monostatic pulsed laser Doppler vibrometer is developed to overcome demodulation failures caused by cochannel interference. We discussed the waveform design guidelines and proposed a digital range gated signal processing method to avoid the “Narcissus” effects. The resulting phase-modulated intermediate frequency (IF) of 40 MHz, which carries the information of target vibration, is demodulated down to the baseband using a specific in-phase and quadrature (I&Q) demodulator. An experiment is carried out at a 23 m standoff with pulse repetition interval of 50 ns, single pulse energy of 0.25 nJ, and pulse repetition frequency of 1 MHz to verify the performance of the prototype. The experimental results show that the pulsed LDV system has the ability to demodulate the acoustic vibration at a stand-off about several dozens of meters using an ultra-low output laser power.