Abstract
A sensor based on a Sagnac topology in reflection is described. The sensor uses the properties of its frequency response in order to obtain a self-referenced signal proportional to the measured signal. The sensor is a versatile structure for the monitoring of static and dynamic physical parameters, which require a small number of optical components and simple signal processing.

Abstract
Dither demodulation of fibre Bragg grating sensors illuminated with multimode light from cheap compact disc laser diodes is investigated. Quasi-static temperature and strain sensitivities of 0.09 degrees C/root Hz and 0.6 mu epsilon/root Hz are obtained. It is shown that small ac signals outside the loop bandwidth can be measured using synchronous detection at double the dither frequency.

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

Abstract
We report on the integration of optical fiber containing Bragg gratings in the structure of both optical and power cables. It is shown that fiber Bragg gratings provide an efficient method to monitor quasi-distributed mechanical strength along optical cables. This technology is also applied to the monitoring of temperature in power cables for transmission/distribution infrastructures. We show that there are no losses introduced during the cabling process, and the temperature sensitivity of the fiber Bragg grating was found to be only slightly affected by the extrusion process. Results are presented for cable operation in real environment.