Continuous distributed temperature monitoring of a long laser-cooled rare-earth-doped glass rod

This study presents the continuous measurement of the temperature distribution along a length of rod-shaped glass sample cooled by anti-Stokes fluorescence. The technique uses a Random Optical Grating by Ultraviolet or Ultrafast Laser Exposure (ROGUE) written in standard SMF-28, interrogated by optical frequency-domain reflectometry (OFDR). Milli-Kelvin resolution with millimeter spatial resolution is demonstrated over 15 cm of sensing length. Comparisons with an FLIR camera and a point fiber Bragg grating sensor show improved performance for monitoring long lengths of laser-cooled samples, and show its potential as a valuable tool for monitoring the temperature distribution in radiation balanced or high power fiber/rod lasers and amplifiers.