Self-suppression of leading-fiber-induced noise for remote fiber-optic interferometric sensor using a dual-wavelength optical signal.

Environmental disturbances in the leading fiber are a significant source of noise in remote fiber optic interferometric sensors (FOIS). As the two interrogation lightwaves propagate through the leading fiber, environmental disturbances can induce undesired demodulated phase noises, collectively referred to as leading-fiber-induced noise. This study proposes what we believe to be a novel method for leading-fiber-induced noises self-suppression, utilizing dual-wavelength optical signals as mutual reference signals, thereby eliminating the need for a reference interferometer. Furthermore, the FOIS doubles the amplitude of the measurement signal, providing a better signal-to-noise ratio (SNR) compared to the traditional reference interferometer method. Experimental results demonstrate that the FOIS achieves an average measurement signal enhancement of 5.93 dB and an average leading-fiber-induced noise suppression of 41.53 dB within the frequency range of 200 Hz to 1800 Hz. leading-fiber-induced noises are significantly suppressed over a 20 km bi-directional transmission, and the system's SNR is comparable to that of a conventional FOIS using identical performance devices. The remote FOIS shows huge advantages for hydrophone shore-based array and towed array applications.