A Miniaturized, Low-Cost Interrogator via Intrapulse Wavelength Demodulation for Operando Fiber-Optic Sensing in Batteries

Fiber optic sensing shows great promise in battery monitoring due to its versatile sensing capability, compact size, flexibility, and electromagnetic immunity. However, the high cost of optical interrogators limits large-scale commercialization. Herein, we develop a low-cost, miniaturized interrogator utilizing off-the-shelf distributed feedback lasers in pulse mode to induce frequency chirping. This design maintains environmental immunity while partially replacing costly spectrum analyzers. Compared to other commercial interrogators, our device excels in cost and scanning rate, achieving a MHz scanning rate with accuracy and repeatability. We demonstrate its successful application in commercial 18650 lithium-ion batteries (LiNi_0.8Co_0.1Mn_0.1O₂/C) by implanting the fiber Bragg grating sensor, and it features time-division multiplexing for monitoring multiple sensing points. Additionally, the techno-economic analysis corroborates the considerable added value of the novel interrogator in diverse application scenarios. Collectively, the development of new interrogation devices will not only advance smarter energy storage systems but also provide insights into next-generation optical sensing devices.