Fig. 1. (a) Schematic diagram and (b) practical picture of a fiber temperature and pressure sensor probe; (c) microscope image of the FP cavity.

Fig. 2. Demodulation process of the FBG and FP cavity cascaded fiber sensor.

Fig. 3. Reflection spectrum of the FBG and FP cavity cascaded fiber sensor (with experiment setup in the inset).

Fig. 4. Response curve of the FBG wavelength to temperature variation.

Fig. 5. Dependence of FP cavity original length and linear cavity length pressure coefficient on temperature.

Fig. 6. Response curves of FP cavity length to ambient pressure at different temperatures.

Fig. 7. FP cavity length stability of the sensor.

Fig. 8. Logging profiling achieved through the sensor probe in the depth range of 2850–3050 m.