Hybrid-enhancement synthesis of dual-interference signals and multiplexing structure optimization for push-pull...

This paper addresses the dual challenges of inter-channel response mismatch and noise floor constraint in inline interferometric fiber Bragg grating (FBG) accelerometers. Although push-pull configurations have been proven to double sensitivity, such FBG implementations require signal synthesis. This necessity arises because 'push' and 'pull' constitute independent interference channels, not dual arms of an interferometer. Crucially, minor structural asymmetry degrades synthesis fidelity, directly reducing sensitivity and elevating the intrinsic noise floor. By establishing a quantitative correlation model, we reveal that a minute 1 mm asymmetry induces a 7 rad response deviation in the dual-channel amplitudes. Herein, we propose an asymmetry-compensated dual-interference-channel synthesis scheme. This scheme employs a dynamic scaling factor (r > 1) to amplify the weaker response, enabling precise channel matching. Owing to the inherent noise incoherence in dual-channel systems, signal synthesis inevitably elevates the noise floor, an effect determined by the multiplexing method. We systematically investigate noise coupling mechanisms across wavelength-division multiplexing (WDM), time-division multiplexing (TDM), and space-division multiplexing (SDM) systems. Quantitative comparisons show that WDM is superior, exhibiting 2.6 dB and 5.6 dB lower noise floor elevation than TDM and SDM, respectively. Building on these insights, we develop a WDM-based push-pull interferometric FBG accelerometer. The optimized sensor attains a high sensitivity of 53.18 dB (re: rad/g) with a low minimum detectable acceleration of 6.43×10 ^{- 8}g/Hz, featuring a simplified optical structure requiring only two pairs of FBGs. The proposed scheme offers a universal solution for asymmetry-induced mismatches, regardless of their origin. Concurrently, through detailed analysis of noise characteristics, the critical design criteria for high-performance sensor multiplexing structures are established.