A High-Speed Distributed Ultra-Weak FBG Sensing System With High Resolution

Abstract

A high-speed high-resolution distributed sensing system with ultra-weak fiber Bragg grating (FBG) array is presented. The scheme uses a narrow bandwidth filter to translate wavelength shift measurement to a simple intensity measurement. By introducing a reference channel into the system to compensate for the intensity fluctuation from the light source or optical fiber bending loss, we can realize high-resolution and high-speed distributed static and dynamic strain measurement using 342 ultra-weak FBGs with reflectivity of 0.01% and spatial resolution of 2.5 m along 855-m optical fiber. The wavelength variation of all gratings was measured as 0.22 pm at a sampling rate of 100 kHz. Experimental results show that the resolution of strain measurement can achieve 222 $\text{n}\varepsilon $ , and dynamic frequency of 2000 Hz is achieved.