Long-distance remote simultaneous measurement of strain and temperature based on a Raman fiber laser with a single FBG embedded in a quartz plate

We propose and experimentally demonstrate long-distance, simultaneous measurement of strain and temperature based on a Raman fiber laser with a single FBG embedded on a quartz plate. Most of all, FBG based sensing technology has attracted considerable attention in the field of optical sensors since FBG based sensing probe can provide the most simple and attractive methods to monitor the external perturbation change like temperature, strain, and pressure due to its high sensitivity, electro-magnetic immunity, compactness, and ease of fabrication. In order to enhance the measurement resolution of sensing systems, fiber lasers based sensor schemes with narrow bandwidth and high extinction ratio have been considered as promising technologies. A novel and practical Raman laser based long-distance sensing scheme for simultaneous measurement of strain and temperature using FBGs is investigated. High-quality Raman laser output with a high extinction ratio of more than 50 dB is obtained at a long distance of over 50 km. Lasing wavelength shift and separation occur as the temperature and strain increase, respectively. To induce these phenomena, half of the FBG is fixed steadily on the quartz plate to respond to temperature only, while the other half of the FBG is free to respond to both temperature and strain. The temperature and strain sensitivities are measured to be 8.96 pm/⁰C and 1.47 pm/με, respectively. This allows simultaneous measurement of strain and temperature for long-distance sensing applications of more than 50 km.