Intensity-independent fiber coupled interrogation technique for fiber Bragg gratings by fiber Bragg gratings

A low cost, highly accurate and light intensity-independent sensor system for the analysis of fiber Bragg grating signals based on fiber Bragg gratings in the detection unit is presented. The setup is based on two fiber Bragg gratings used in reflection to analyse one sensing fiber Bragg grating. The Bragg gratings were inscribed in coated non-photosensitive standard telecommunication fibers using an infrared femtosecond laser and the point-by-point writing technique. The accuracy of this interrogation concept is presented by means of a temperature measurement with a resolution better than 0.12°C in a linear operation range of 20°C.