High-speed multiplexed fiber laser acoustic emission sensing system using 3x3 coupler and FPGA parallel processing algorithm

This paper proposes a wavelength-division multiplexing fiber laser acoustic emission sensing technique based on 3x3 coupler type interrogation method and a FPGA parallel processing algorithm. Narrow- linewidth (about 3 kHz) single-frequency distributed feedback fiber lasers are used for acoustic emission probes. A NI FlexRIO device is used to acquire the original signals from the photodetectors. A symmetric demodulation algorithm is executed in the FPGA using parallel data processing structure. The acoustic emission sensing system with four parallel channels and 2 MHz sampling rate achieves a wavelength resolution of 2 x10(-7) pm/vHz @ 100 kHz.