Demodulation Method of Identical Ultra-Weak Fiber Bragg Grating Array Based on Golay Code

Abstract

A noise-resilient demodulation technique is proposed and demonstrated with a Golay coded optical pulse source, for a quasi-distributed sensor array constructed by identical ultra-weak fiber Bragg gratings (UWFBGs). We set up a light source, which line width is over 20GHz, to avoid the interference between adjacent gratings as a result of wide optical pulses in coded pulse train. Attributed to the special autocorrelation property of Golay code, wavelength demodulation of the identical UWFBGs is achieved with improved noise resistance. With a 32-bit Golay coded pulse train, temperature sensing is achieved with 3-m spatial resolution over a 9.06-km UWFBG array. The signal-to-noise ratio (SNR) of the time-domain signal is increased by 6.9 dB, as compared to the case when an uncoded pulse train is adopted. The proposed decoding algorithm can remove the requirement for complex decoding hardware, leading to a greatly simplified experimental setup.