In-fiber Long-period Grating and Fiber Bragg Grating-based Sensor for Simultaneously Monitoring Remote Temperature and Stress

In this study, we experimentally demonstrated that a high-sensitivity fiber sensor can be used for the remote sensing of temperature and stress simultaneously. The proposed sensor includes several sensing heads, each of which is composed of a long-period grating (LPG) and a fiber Bragg grating (FBG). Moreover, the optical characteristics of both the FBG and LPG are different. On the basis of these different optical features and the sensing transfer matrix, temperature and stress can both be remotely measured simultaneously. The temperature sensitivities of the grating-wavelength shift and grating-reflection intensity are about 0.0082 nm/degrees C and 0.044 dBm/degrees C, respectively. The strain sensitivities of the grating wavelength shift and grating-reflection intensity are respectively around 0.0133 nm/g and 0.0089 dBm/g. Therefore, the fiber sensor can provide a simple method with excellent sensitivity for applications of structure-security monitoring and industrial engineering measurements.