ABSTRACT
Fiber sensors can be designed such that the measurand interacts with one or several optical parameters of the guided light (intensity, phase, polarization, and wavelength). Independent of the sensor type, the light modulation must be processed into an optical intensity signal at the receiver, which subsequently performs a conversion into an electric signal. In general, the main interest in this type of sensors comes from the fact that the optical ber itself oers numerous operational benets. It is electromagnetically passive, so it can operate in high and variable electric eld environments (like those typical of the electric power industry) and where there is explosion risk; it is chemically and biologically inert since the basic transduction material (silica) is resistant to most chemical and biological agents; its packaging can be physically small and lightweight. Considering the intrinsic low optical attenuation of the ber (around 0.2 dB/km), it is possible to attain distributed sensing, that is, determine the measurand as a function of the position along the length of the ber interrogating from only one end. Also, the optical ber can be operated over very long transmission lengths, so the sensor can easily be placed kilometers away from the monitoring station. In addition to this, it is also possible to perform multiplexed measurements using large arrays of remote sensors, operated from a single optical source and detection unit, with no active optoelectronic components located in the measurement area, thereby retaining electromagnetic passiveness and environmental resistance (Ansari and Libo 1998, Tao et al. 2000, LópezHiguera 2002, Wan and Leung 2007, Gagliardi et al. 2010, Cusano et al. 2011, Pevec and Donlagic 2011, Yang et al. 2007).
