Suppression of leading-fiber-induced noise in remotely fiber-optic interferometric sensor

Environmental disturbances in the leading fiber are a significant source of noise in remote fiber optic interferometric sensors (FOIS). Typical noise suppression methods mainly use additional reference interferometers, increasing the volume and cost of the system, and the difference between the reference and sensing interferometers results in limited noise suppression effect. This study proposes a new fiber optic interferometric sensor that utilizes dual-wavelength optical signals based on heterodyne demodulation. The contributions of leading-fiber-induced noises are shared by both the two wavelength optical signals and are further suppressed through heterodyne demodulation. The proposed FOIS is capable of suppressing the leading-fiber-induced noise by themselves without additional reference interferometer. In the proposed FOIS, the "sensing unit" and the "reference unit" are co-located in the same environment, enabling higher noise suppression while avoiding SNR degradation, increased volume, and higher costs associated with using reference interferometers. Experimental results demonstrate that the FOIS achieves an average leading-fiber-induced noise suppression of 41.36dB within the frequency range of 200Hz to 1800Hz. The remote FOIS show huge advantages for hydrophone shore based array and towed array.