Frequency Response Enhancement of DAS Based on Space-Time Division Multiplexing of MCF

The trade-off between the frequency response and the sensing distance limits the ultrasonic detection ability of distributed acoustic sensors (DAS) over long distances. This work proposes a space-time division multiplexing (STDM) method based on multi-core fiber (MCF) to enhance the frequency response of DAS. The frequency response of STDM can be enhanced by 7 times, which depends on the number of cores used. By injecting probe pulses with various time delays into different cores in MCF, the back Rayleigh scattering signals with different time delays can be obtained without crosstalk. The feasibility of STDM has been well-verified in experiments with the frequency response enhanced by 1.5 times.