A dual-parameter sensor for strain and temperature measurement featuring cascaded LPFG-FP structure

A dual-parameter sensor for strain and temperature measurement featuring cascaded long period fiber grating and Fabry-Perot (LPFG-FP) structure has been proposed and realized both theoretically and experimentally. The sensor structure is theoretically proved to be efficient, where the LPFG serves as a passive filter. The direct point-by-point method of CO2 laser system is used for LPFG fabrication. The FP structure is fabricated by splicing the chemically etched SMF and the end of LPFG. The total sensor length is 3.6 cm, and three dips at 1544.18 nm, 1556.27 nm, and 1566.92 nm are chosen for following analysis. The strain experimental results show that in the range of 0-450με, the strain sensitivities are 1.7 pm/με, −8.2 pm/με, and 1.5 pm/με of three dips, respectively. The temperature experimental results show that in the range of 40-70℃, the temperature sensitivities are 6.8 pm/℃, 21.0 pm/℃, and 7.1 pm/℃ of three dips, respectively. By analyzing wavelength shifts and parameter response characterization of the resonant wavelengths, the sensitivity matrix can be determined. The experimental results demonstrated the satisfactory performance of strain and temperature measurement.