Abstract
A theoretical and experimental study of the self-referencing resonant fiber optic intensity sensors based respectively on Michelson and Mach-Zehnder configurations is conducted. Sensor linearity and sensitivity are addressed, being also considered sensors design and optimization.

Abstract

Abstract

Abstract
We present a closed-loop technique for measuring wavelength shifts associated with fiber Bragg gratings by using a fused biconical wavelength division multiplexer (WDM). The spectral response of the WDM is actively tuned by stretching of the coupling region to maintain a fixed coupling ratio at the reflected Bragg wavelength. The closed-loop operation allows sensitivities usually associated with a highly selective WDM to be obtained without compromising the measurement range. A simple theoretical model is presented together with experimental results for temperature and strain measurements. (C) 1998 Optical Society of America.

Abstract
A digital signal processing technique for interferometric peak localization in white Light sensing systems is presented. The procedure is based on computational processing of the acquired interferometric signal using Fourier mathematical operations for fringe visibility improvement. Tests are made by computer simulations. (C) 1998 American Institute of Physics. [S0034-6748(98)03807-6]

Abstract
A demodulation scheme for fiber Bragg grating (FBG) sensors is presented. It is based on the generation of an electrical carrier by using a modulated multimode laser diode to illuminate the fiber grating. The change in Bragg wavelength is measured by tracking the phase of the carrier at the detector output in either an open- or a closed-loop scheme. A theoretical analysis of the interrogation technique in terms of linearity and dynamic range is presented. Experimental data were obtained for both strain and temperature measurements. Sensitivities of 0.7 mu epsilon/root Hz and 0.05 degrees C/root Hz were obtained over a dynamic range of approximate to 60 dB, The application of this demodulation scheme to a multiplexed sensing system is also demonstrated.