Bragg grating tuned fiber laser system for measurement of wider range temperature and strain

Abstract

A Bragg grating-tuned fiber laser-based sensor system has been developed to measure over a wide range of temperatures (22–500 °C) and strain (0–1200 με) using both a normal grating and a chirped grating as optical feedback elements and Er3+-doped fiber as the active gain medium. A high reflectivity normal Bragg grating was written into a specially fabricated high temperature sustaining Sb–Ge co-doped photosensitive fiber and a chirped grating was inscribed into a commercial B-Ge co-doped fiber, due to its higher photosensitivity. The shift in the laser wavelength was monitored in this system when the normal grating was temperature or strain-tuned, with it also forming the active element of the sensor head of the system. The root mean square (RMS) error values of the active sensor system were found to be 2.6 °C and 28.3 με over the above measured ranges of temperature and strain, respectively.