Ultra-high-speed demodulation system of the weak FBG sensor based on multi-wavelength REC-DFB laser array

We propose an ultra-high-speed demodulation system of the weak fiber Bragg grating (wFBG) sensor utilizing an 8-channel multi-wavelength reconstruction-equivalent-chirp distributed feedback (REC-DFB) laser array in conjunction with integrated switching semiconductor optical amplifiers (SOAs). The REC technique not only simplifies the fabrication process of the DFB lasers' gratings, but it also guarantees superior single-mode performance, crucial for effective sensing applications. By utilizing the laser array along with on-chip integrated switching SOAs, this system can generate a cyclic pulsed laser output. This enables accurate retrieval of both location and wavelength data for the wFBG from the reflection spectra during each pulse cycle. The proposed system achieves an ultra-fast wavelength demodulation rate of 2.5MHz when measuring the wFBG sensor, significantly improving the demodulation speed for traditional wavelength-swept time-division multiplexing (TDM) sensing networks. Experimental results indicate that the demodulation error remains below ±5pm over 500 periods.