Simultaneous Measurement of Gas Pressure and Temperature Based on MZI Cascaded with FBG

An optical fiber sensor based on Mach-Zehnder interferometer (MZI) cascaded with a fiber Bragg grating (FBG) for simultaneous measurement of temperature and gas pressure is proposed and demonstrated. The MZI is fabricated by inserting a piece of tapered SMF in between two sections of MMF, which performs as the gas pressure sensing element. A FBG is cascaded with the MZI to eliminate the temperature induced wavelength shift of the MZI due to the thermal optic and thermal expansion effect of silica. Experimental results show that the MZI with gas pressure and temperature responses of -8.82 nm/MPa and 33.1 pm/℃ respectively. The FBG exhibits a temperature response of 12.3 pm/℃ and shows insensitive to gas pressure. By tracing the transmission dips of the MZI and FBG simultaneously, gas pressure and temperature variation can be monitored at the same time.