Chirped-FBG-Assisted Weak-FBG Demodulation Method and Its Application in Quasi-Distributed Temperature Sensing and Battery Monitoring

Thermal runaway of the power battery can pose serious security risks. Therefore, it is imperative to monitor and control battery temperature in real time. To address the shortcomings of existing fiber Bragg grating (FBG) based temperature demodulation methods on efficiency, accuracy, and cost, a chirped-FBG (CFBG) slope-assisted weak-FBG (wFBG) demodulation method is proposed in this paper. The core mechanism of this method involves using the rising edge of the CFBG transmission spectrum as a wavelength-selective filter for wavelength-addressing series-connected identical wFBGs. In the proposed system, all optical components are fiber-coupled, thereby providing advantages such as low cost and compact size. The experimental results reveal that the system can operate stably at a demodulation rate of 1 Hz within 33°C to 107°C, with a demodulation standard error of 0.0831°C. The temperature demodulation resolution is 1.73×10-4°C, equivalent to a spectrometer demodulation resolution of 1.6 fm. By deploying the system on battery cells, online monitoring of global temperature in power batteries with high sensing density can be realized, providing a feasible technical solution to enhance monitoring precision, real-time performance, economic efficiency, and implementation convenience for the temperature monitoring requirements of battery management systems and thermal management systems.