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Phase drift noise suppression for coherent-OTDR sensing based on heterogeneous dual-sideband LFM pulse

A distributed acoustic sensing with digital differential coherent optical time-domain reflectometry based on heterogeneous dual-sideband linear frequency-modulated (LFM) pulse is proposed. The positive and negative LFM signals are loaded on the upper and lower optical sidebands respectively. The loaded signals with the same spectrum width but opposite slope chirps will result in an opposite interference pattern movement. By performing the digital difference on the phase demodulation results of the two sidebands, the sensitivity at 1 kHz is doubled at least and the suppression of 27.26 dB in the low-frequency common-mode phase drift noise is obtained at 10 Hz.