Sensoriamento utilizando interferômetros do Sagnac em fibra na região do infravermelho e terahertz
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Data
2025-12-12
Autores
Pizzaia, João Paulo Lebarck
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Universidade Federal do Espírito Santo
Resumo
Optical sensors stand out for their high sensitivity, reduced dimensions and weight, immunity to electromagnetic interference, and safety in potentially explosive environments. Among the various existing configurations, the Sagnac interferometer is widely recognized for its use in high-precision optical gyroscopes, but it has been increasingly employed in sensing applications of different physical quantities due to its high sensitivity. However, as occurs in other fiber-optic systems, its practical implementation may be limited by the cost associated with optical components and analysis instruments, such as the optical spectrum analyzer (OSA). In this Thesis, the mathematical modeling and the numerical and experimental development of different Sagnac interferometer configurations are presented, ranging from simple setups to arrangements with multiple optical elements in the loop. The focus of the work is on reducing the implementation and maintenance costs of Sagnac optical interferometers without compromising sensitivity, as well as on proposing new applications operating in the terahertz spectral region. In one of the proposed configurations, a force sensor based on a simple Sagnac interferometer setup was developed, using standard single-mode fiber as the sensing element in place of the polarization maintaining fiber usually employed. This modification enabled reliable measurements with a sensitivity of–0.116 nm/N, in addition to significantly reducing maintenance costs, since fiber replacement is low-cost in the event of rupture due to overload. For vibration monitoring, a simplified configuration capable of operating over a wide frequency range (50–22,000 Hz) was implemented, achieving a correlation coefficient (R2 = 0.9696) for frequency detection. In the terahertz region, a refractive index sensor based on photonic crystal fiber was modeled and simulated, yielding correlation coefficients of 0.999 and 0.987 for third- and second-order polynomial fits, respectively. The results demonstrate that the proposed configurations maintain high levels of sensitivity while employing less complex sensing systems. Thus, this work contributes to advances in the research and development of optical sensors based on Sagnac interferometers, making them simpler, more accessible, and more viable alternatives for scientific applications.
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Interferômetro de Sagnac , Sensor , Fibra óptica , Palavra-chave , Palavra-chave