Enhanced Sensitivity for Dynamic Pressure Measurements Using a Fiber-Optic FPE Sensor via Programmable Vernier Envelope Acquisition

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Owing to its diaphragm-free structure, the fiber-optic Fabry-Perot etalon (FPE) sensor exhibits an exceptionally large dynamic range and rapid response characteristics for dynamic pressure sensing. However, its practical application is significantly impeded by its inherently low sensitivity. The optical Vernier effect has been demonstrated as an effective tool for enhancing the sensitivity of fiber-optic interferometric sensors. Previous studies have primarily focused on the design of Vernier-effect-based sensors via various cascaded interferometer configurations for sensitivity enhancement. In practical implementations, an interrogation system comprising a broadband light source and an optical spectrum analyzer (OSA) is typically employed to capture the Vernier spectrum. However, the fixed cavity length of the reference interferometer inherently restricts the flexible adjustment of sensitivity for such sensors. Furthermore, the low sampling rate of conventional OSAs fundamentally limits the dynamic sensing performance of Vernier-effect-based sensors. In this study, we propose a programmable Vernier envelope acquisition (PVEA) technique based on a modulated grating Y-branch (MG-Y) laser for enhancing the sensitivity of FPE sensors. The MG-Y laser performs wavelength scanning over the range of 1527–1567 nm with a sampling interval (SI) of 8 pm, thus enabling the acquisition of the transmission spectrum of the FPE sensor and its corresponding free spectral range (FSR). Benefiting from the flexible wavelength tuning capability of the MG-Y laser, the Vernier envelope was acquired by programmatically adjusting the laser's wavelength sampling interval, ultimately enabling different levels of sensitivity amplification for the FPE sensor without relying on an OSA. The technique was validated using an FPE sensor with a cavity length of 1500 μm, achieving sensitivity enhancement factors of 11.10 and 17.69. Dynamic pressure sensing was successfully demonstrated, exhibiting a measured response time of 320 ms. Furthermore, this technique is adaptable to other types of interferometric sensors.

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