Characterization of Bragg grating with optical fibers

We report characterization of fiber Bragg grating spectra, subjected to ext ernal changes of temperature and strain. Pie applied the basic theory of di electric thin him layers to describe the behaviour of gratings under such c hanges. This characterisation suggests a quasi-distributed temperature or s tarin sensor. In addition, this characterization allows to measure the firs t and second order thermal-optic coefficient; and the first order elast-opt ical coefficient, representing an alternative technique for its determinati on.