Robust and high-efficiency demodulation of ultra-weak FBG arrays in OFDR-based distributed sensing

A robust and high-efficiency demodulation scheme for optical frequency domain reflectometry (OFDR) based ultra-weak fiber Bragg grating (UWFBG) array detection system, originating from the Buneman frequency estimation (BFE) algorithm, is proposed and experimentally demonstrated. Due to the current limitations and imperfections of FBG inscription technology, the quasi-continuous inscription approach, along with its less-than-ideal outcomes, gives rise to problems of grating spectrum splitting and spectral distortion during the grating demodulation process. This renders the traditional approach of directly applying the BFE algorithm for grating demodulation ineffective, despite its significant enhancement of demodulation efficiency. To address this issue, we propose utilizing the BFE algorithm for the demodulation of rough cross-correlation spectra of FBGs. This approach leverages the inherent noise resistance of the cross correlation algorithm while also capitalizing on the efficiency improvements offered by the BFE algorithm, ultimately achieving a simultaneous enhancement in demodulation efficiency while ensuring robust demodulation performance. In the demonstration experiments, by employing the proposed algorithm, we achieved demodulation results that were virtually indistinguishable from those of traditional demodulation methods, while simultaneously enhancing the demodulation efficiency by 15.3 times (10-m measurement range). This algorithm facilitates the progress of OFDR-based UWFBG sensing towards practical applications.