Simulation of a Chirped FBG and EFPI-Based EC-PCF Sensor for Multi-Parameter Monitoring in Lithium Ion Batteries

The growing need for efficient and safe high-energy lithium-ion batteries in electric cars and grid storage requires sophisticated internal monitoring solutions. This work demonstrates the first integrated ethylene carbonate-filled photonic crystal fiber (EC-PCF) sensor with a chirped Fiber Bragg Grating (FBG) and an Extrinsic Fab-ry-Pérot Interferometer (EFPI) for multifunctional Refractive Index (RI), temperature, strain, and pressure measurement in one multiplexed platform for Lithium-Ion Batter-ies(LIBs). By making the refractive index of the PCF cladding the same as that of the battery electrolyte with ethylene carbonate, the sensor is maximized in light–matter interaction for its RI sensitivity, and the cascaded EFPI maximizes detection of mechanical deformation over conventional FBG arrays. The model applies Transfer Matrix Method with Gaussian apodization for FBG reflectivity in steady-state conditions and Airy formula for high-precision EFPI spectra such as stress-induced birefringence, TE/TM polarization modes, and dispersion dependent on the wavelength in a 1540–1560 nm range. Fabrication variation and environmental noise robustness is analyzed by Monte Carlo simulations with Sobol sequences with resulting temperature sensitivities of ∼12 pm/°C, strain sensitivities of ∼1.10 pm/µε, and RI sensitivities of ∼1200 nm/RIU. Corroborated with a simulated Li-ion cell, this system is a reliable foundation for real-time battery monitoring and opens the door to experimental applications and advanced battery management systems.