Dual-comb-enhanced spectroscopic fiber Bragg grating sensing with over 100-dB dynamic range and nanostrain sensitivity

Achieving ultra-high sensitivity simultaneously with a large dynamic range remains a fundamental challenge in fiber Bragg grating (FBG) sensing. Conventional interrogation methods, such as continuous-wave edge detection, are inherently constrained by a rigid trade-off between the linear tracking range and detection sensitivity. Here, we overcome this limitation by demonstrating a spectroscopically enhanced interrogation scheme based on electro-optic dual-comb interferometry. Unlike prior approaches focused primarily on spectral resolution, we exploit the full-spectrum access of dual-comb spectroscopy to perform a phase-aligned vector summation of the response across multiple comb lines within the FBG resonance. This coherent aggregation strategy, combined with balanced detection, effectively suppresses common-mode laser noise and yields a theoretical √N signal-to-noise ratio (SNR) improvement. Experimentally, we achieve a 15 dB sensitivity enhancement over conventional methods, demonstrating a noise-limited strain resolution of 0.9 nε/√Hz at 1 kHz and a dynamic range exceeding 105 dB. By fundamentally resolving the conflict between precision and measurement bandwidth, this architecture offers a robust pathway for next-generation vibro-acoustic detection in applications ranging from underwater acoustics to structural health monitoring.