Name: JOAO PAULO LEBARCK PIZZAIA
Publication date: 12/12/2025
Examining board:
Name |
Role |
|---|---|
| ARNALDO GOMES LEAL JUNIOR | Coorientador |
| CAMILO ARTURO RODRIGUEZ DIAZ | Examinador Interno |
| CARLOS ALBERTO FERREIRA MARQUES | Examinador Externo |
| CARLOS EDUARDO SCHMIDT CASTELLANI | Presidente |
| MARCELO MARTINS WERNECK | Examinador Externo |
Pages
Summary: Optical sensors stand out for their high sensitivity, reduced size 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 has been
increasingly employed for sensing different physical quantities due to its high sensitivity. However, as in
other fiber-optic systems, the main obstacle to its widespread implementation remains the high cost
associated with complex and expensive optical components. This Thesis presents the mathematical modeling
and experimental development of different Sagnac interferometer configurations, ranging from simple
setups to more complex arrangements with multiple optical elements in the loop. The main focus of this
work is to reduce implementation and maintenance costs without compromising sensitivity, while also
exploring new applications operating in the terahertz spectral region. In one of the proposed configurations,
a force sensor was developed based on a simple Sagnac interferometer setup using standard single-mode
fiber as the sensing element, replacing the polarization-maintaining fiber commonly employed. This
modification enabled reliable measurements with a sensitivity of –0.116 nm/N while significantly reducing
maintenance costs, since fiber replacement is inexpensive in the event of breakage due to overload. For
vibration monitoring, a simplified configuration was implemented, achieving a wide operational frequency
range (50–22,000 Hz) with high precision and repeatability. In the terahertz region, a refractive index sensor
based on a 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 sensitivity levels while substantially reducing implementation and maintenance
costs. Therefore, this work contributes to the advancement of research and development of optical sensors
based on Sagnac interferometers, making them simpler, more cost-effective, and viable alternatives for
scientific and industrial applications.
