Time-delay compensation to reduce the influence on laser-introduced phase noise suppression in an optical fiber sensing array

In a fiber sensing array, the time delay between channels significantly impacts the suppression of laser-introduced phase noise (LPN) through the reference interferometer scheme. A method for suppressing the impact of time delay, which includes the measurement and compensation, is proposed. Time delay in the entire 5-element sensor array is determined by calculating the phase difference between the calibrated signals, while compensating for the time delays between the sensing signals and the reference signal is achieved through temporal shifting of digital signal sequences. The experimental results show that the time-delay effect is suppressed in four channels of delay-sensing signals, with the suppression effect of 23.1-26.8 dB. Additionally, the compensated sensing signal exhibits a background noise ratio that differs by 5-8 dB compared to the non-delayed sensing signal. The correlation between time-delay residual and sampling rate is verified by theoretical analysis and experiments. If time-delay residual can be effectively reduced, the compensation effect can be optimized whether the sampling rate is increased or decreased. The proposed method effectively compensates for inter-channel time delay and introduces an optimization approach to enhance the compensation effect, thereby facilitating effective suppression on the influence of LPN in the sensing array.