We propose a wavelength-division multiplexing (WDM) fiber Bragg grating (FBG) array designed to mitigate the spectral shadow effect, thereby enhancing multiplexing capacity. The array comprises 7560 FBGs, which are periodically arranged across 21 distinct wavelength channels. Each FBG has an average reflectivity of 5.5‰ and a bandwidth of 0.113 nm. We employ an optical frequency-domain reflectometry (OFDR) system for interrogation, which enables high-density array demodulation and large-strain measurement. A convolutional localization algorithm is proposed to achieve fast and accurate addressing of each FBG. The sensing system achieves a maximum sensing-fiber length of 120 m and spatial resolution of 16 mm, along with a demonstrated strain range of 10000 με and wavelength accuracy of 1.2 pm. Furthermore, a 21-fold enhancement in spectral demodulation speed is realized over identical FBG arrays. Consequently, the average demodulation time per FBG is substantially reduced from 11.25 ms to 0.53 ms. These results affirm the exceptional suitability of our system for applications demanding high precision, an extensive strain range, and substantial sensor capacity.

We have numerically and experimentally investigated the flow rate measurement of the pipeline based on the optical fiber. Employing the large eddy simulation (LES) model, we have quantitatively analyzed the pressure fluctuation of the pipe wall caused by the turbulent flow in the pipeline. The simulation results have shown that the standard deviation of pressure fluctuation was quadratic with the flow rate. We have verified the theoretical model by using a distributed optical fiber acoustic sensing (DAS) system in the flow rate range from 0.61 m/s to 2.42 m/s. The experimental results were consistent with the simulation results very well. Furthermore, to improve the measuring error at the low flow rate, we have employed the composite adaptive denoising algorithm to eliminate the background noise and system noise. The final results have shown that the minimum goodness of fit was improved from 0.962 to 0.997, and the variation of the quadratic coefficient significantly decreased by 93.25%. The measured flow rate difference was only 0.84% between different sensing points in repeated experiments.