Desenvolvimento de sensores baseados em fibra óptica afunilada para monitoramento ambiental

Abstract

The monitoring of environmental parameters is important in preserving the environment. The development of technologically advanced systems for measuring physical parameters allows the early detection of harmful environmental factors. For example, refractive index and temperature measurement systems can detect thermal and chemical pollution in rivers water. Curvature or tilt measurement is important in predicting natural phenomena that may cause damage to human beings, such as landslides and earthquakes. This thesis investigates sensors based on tapered optical fiber for monitoring environmental parameters. The investigated technology is based on standard single-mode optical fiber with tapered section that makes use of the evanescent field to detect changes in the external environment, such as refractive index, temperature and curvature. This type of device is analyzed through numerical simulations and experimental measurements. The numerical modeling is performed using finite difference beam propagation method (FD-BPM). It is numerically and experimentally demonstrated that once tapered optical fiber Michelson interferometer is subjected to bending the sensitivity to refractive index change is enhanced in comparison with the not bent device. Experimental measurements indicate that this type of device has great potential as a temperature sensor. Numerical results, based on FD-BPM, indicate that it is possible to optimize the taper parameters in optical fiber to improve its sensitivity to bending in terms of transmitted power.