Simultaneous measurement of gas pressure and temperature based on Fabry–Pérot cavity cascading fiber Bragg grating

A novel optical fiber sensor with the ability to simultaneously measure gas pressure and temperature is proposed and experimentally demonstrated. The sensor comprises a fiber Bragg grating (FBG) and Fabry–Pérot interferometer (FPI) cascading; the FPI consists of two sections of single mode fiber splicing a short quartz capillary with a gas channel prepared by femtosecond laser micromachining that circulates the Fabry–Pérot cavity with external gas. Because the open cavity FPI is only sensitive to gas pressure and extremely less sensitive to temperature, while FBG is only sensitive to temperature and insensitive to gas pressure, an extremely simple diagonal matrix of sensitivity is obtained. The diagonal matrix elements are temperature and gas pressure sensitivity, corresponding to 0.012 nm/°C and 4.14 nm/MPa, respectively. Experimental results show that the sensor structure can realize the simultaneous measurement of gas pressure and temperature and eliminate the cross sensitivity between the gas pressure and temperature. The proposed sensor has the advantages of compact structure, simple fabrication, and convenient packaging and has a wide application prospect in the field of simultaneous measurement of gas pressure and temperature.