Estudo sobre interferômetro de Fabry-Perot em fibras ópticas para aplicação em sensores

Abstract

This work presents the development and experimental characterization of a fiber-optic Fabry-Perot Interferometer (FPI), aiming for its consolidation as a versatile platform to enhance the detection capabilities of sensing systems. The research initially focuses on the fundamental analysis of the device's interferometric properties, subsequently validating its efficacy through hybridization with a refractive index sensor based on Multimode Interference (MMI). The methodology involved characterizing two extrinsic FPI architectures: a micrometrically adjustable air-gap cavity and a solid-state cavity composed of a sodium polystyrene sulfonate (PSSH) thin film. Experimental results confirmed the precision of Free Spectral Range (FSR) control as a function of cavity length, allowing for the fine-tuning of interference fringes. In the application stage, the FPI was integrated into a refractive index sensor based on MMI fabricated using a singlemode-multimode-singlemode (SMS) structure. The hybrid system was tested with water and glycerin solutions (0% to 40%). The hybridization allowed the high-frequency fringes of the FPI to modulate the broad envelope of the MMI, acting as fine spectral markers. This configuration significantly optimized the ability to identify spectral shifts and detect refractive index variations with greater precision and visual clarity. The use of the PSSH film, with an estimated thickness of 387,12𝜇𝑚, provided the device with increased compactness and stability, establishing a versatile platform for real-time monitoring.