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High-Speed Interrogation System for Fiber Bragg Gratings With Buffered Fourier Domain Mode-Locked Laser

2021; IEEE Sensors Council; Volume: 21; Issue: 15 Linguagem: Inglês

10.1109/jsen.2021.3079191

1558-1748

Tatsuya Yamaguchi, Wataru Endo, Yukitaka Shinoda,

Photonic and Optical Devices

We develop a high-speed interrogation system with a wavelength-swept laser for sensing multiplexed fiber Bragg gratings (FBGs). High-speed and multipoint sensing is achieved by means of a buffered Fourier domain mode-locked (FDML) laser, a recently proposed high-speed wavelength-swept laser. This laser increases the measurement rate several times by tailoring the laser output with a buffer stage. The developed buffered FDML laser successfully achieves a measurement rate of 202.8 kHz using a general FDML laser driven at a sweep rate of 50.7 kHz. In order to detect reflection signals of FBGs at the high measurement rate, the measurement system introduces digital signal processing using a field programmable gate array (FPGA). However, FBG measurements with wavelength-swept lasers are affected by the propagation time (delay) in the optical fiber connecting from the laser to the FBG sensor, which reduces measurement accuracy. To overcome this limitation, the developed system uses a delay correction method with bidirectional sweep of the buffered FDML laser. The interrogation system with the buffered FDML laser achieves a time resolution of 4.9 μs without being affected by the delay.