Differential FBG sensor for simultaneous dual-measurement of pressure and temperature

A differential FBG sensor for simultaneous dual-measurement of pressure and temperature is designed. The bellows generate axial displacement under the action of osmotic pressure. Then the axial displacement passes to the free end of the equi-intensity cantilever beam, and the equi-intensity cantilever beam generates a deflection change. The deflection change makes the center wavelengths of the FBGs attached to the upper and lower surfaces of the cantilever beam shift. The osmotic pressure is obtained by detecting the difference between the center wavelengths of the two FBG; and the temperature is obtained by detecting the mean of the center wavelengths of the two FBG. Sensor test results show that the osmotic pressure sensitivity of the sensor is 1.982 nm/MPa, its linearity is about 0.97%, the repeatability is 3.5% FS; the temperature sensitivity of the sensor is 0.009 5 nm/°C, its linearity is about 3.4%. The sensor achieves the double parameter testing of osmotic pressure and temperature by using the differential structure and appropriate data processing method.