Abstract
A self-referenced fibre optic intensity sensor supported by a multiple beam Sagnac configuration is investigated. Sensor linearity and sensitivity are analysed. Theoretical and experimental results are compared, being considered the sensor design and its optimisation.

Abstract
An investigation is performed on the characteristics of two self-referencing resonant fiber optic intensity sensors supported by a Michelson topology. The sensors are based in transmissive and reflective configurations respectively. Via the definition of the measurement parameter (R parameter) the sensitivity and Linearity of the sensors are analyzed. The problem of sensor design and optimization is considered and the features of the two configurations are addressed.

Abstract
A closed loop technique for measuring Bragg wavelength shifts based on active wavelength tuning of a WDM coupler is presented. By stretching the coupling region of a fused biconical WDM, the 3 dB point is set by the feedback loop to always match the reflected Bragg wavelength. With this scheme, sensitivities usually associated with highly selective WDM can be obtained without compromising the measurement range.

Abstract
A technique for the demodulation of fiber Bragg grating (FBG) sensors based on the use of a second wavelength-matched FBG receiver to track wavelength shifts from the FBG sensor is analyzed, particularly regarding its sensitivity as determined by primary noise sources. Numerical and experimental results show that there is an optimum Bragg wavelength difference between the two FBG's that maximizes the sensitivity for this demodulation technique. (C) 1997 Optical Society of America

Abstract
A passive self-referencing all-fibre technique for Bragg wavelength detection using a biconical fibre filter is described. This filter, basically a tapered depressed-cladding fibre, exhibits a periodic spectral power dependence which permits direct tracking of wavelength shifts in a 20nm unambiguous range. Dynamic strain resolution of 1.5 mu strain/root Hz has been achieved.

Abstract
Progressive ladder topology is studied by consideration of its properties of power budget and coupler tailoring. Optimization criteria are addressed for lossless and real systems, and their basic characteristics are compared with other topologies. Numerical results are presented, and an experiment is described for the case in which the network supports interferometric and intensity (with referentiation) fiber-optic-based sensors.