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SNR enhancement for FDM phase-sensitive OTDR using phase-frequency modulation method
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DOI：10.1016/j.optlastec.2025.112980.png)
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Abstract
En 中文
Frequency division multiplexing (FDM) is used for high frequency response in the phase-sensitive optical time domain reflectometer (Phi-OTDR) system. However, the redistribution of probe pulse energy into bilateral bands by the Mach-Zehnder modulator results in a deterioration of the signal-to-noise (SNR) in FDM Phi-OTDR systems. A phase-frequency modulation method for compensating for the energy loss of probe pulses is proposed. The maximum compensation of the probe pulse energy is achieved when the conjugated phase-frequency modulation signal is applied as the matched filter in the pulse compression process. Experimental results demonstrate the SNR of the restored sinusoidal acoustic signals with frequencies below 11 kHz can reach approximately 46 dB over 21.6 km optical fiber using a six-channel sensing system. Compared with the restored signals of conventional FDM Phi-OTDR system, the SNR of the restored 4.3 kHz sinusoidal acoustic signal is improved by 7.81 dB, enhancing the system's SNR effectively. This innovative approach presents a promising prospect for the practical engineering applications of fiber optic sensing technology in detecting weak signals at high frequencies.
Keywords:
Distributed acoustic sensors
Frequency division multiplexing
Pulse compression