Dense temporal multiplexed fiber Bragg grating sensing based on single-photon detection

Temporal multiplexed fiber Bragg grating (FBG) sensing system for detecting physical parameters with a high spatial resolution is desirable for applications such as structure health monitoring, oil and gas exploration, geophysical research, etc. However, due to the trade-off between bandwidth and sensitivity of the linear photodetection, the wavelength resolution of dense temporal multiplexed FBG sensing system is severely affected under a spatial resolution of centimeters. In this paper, we propose and demonstrate a dense temporal multiplexed FBG sensing scheme with single-photon detection at 1.5 m. A proof-of-principle demonstration is implemented by using three FBG sensors spliced along a piece of fiber. The spatial resolution can reach 5.0 cm which is determined by a time jitter of superconducting nanowire single-photon detector and a pulse width of laser. In our experiment, by using the dual-wavelength differential detection method, a wavelength resolution of 0.5 pm over a range of 550 pm is obtained with a corresponding temperature resolution of 0.05, which could be further improved to 0.01 by increasing the repetition rate of laser pulse.