Design of fiber optic F-P cavity pressure sensor based on bellows

To meet the need of the measurement in high temperature and high pressure in oil and gas well, an optical fiber extrinsic Fabry Perot (F-P) cavity pressure sensor based on bellows is developed. The probe of the sensor is fabricated by CO2 laser thermal bonding in high temperature technique, and is fixed and sealed by high temperature hot melt of low melting point glass solder and adhesive. The measured medium is isolated from the fiber F-P cavity by corrugated diaphragm which can transmit pressure simultaneously, and the change of the length of F-P cavity is compensated in temperature changing with cascading fiber bragg grating.The sensor has characteristics of large dynamic range, high resolution, high repeatability, long term operation stability and high temperature resistance. The pressure measuring range is 0~71MPa, the repeatability is 0.02% F·S, the hysteresis is less than 0.02% F·S, the long term stability is less than 0.03MPa/y, and the sensor can satisfy the requirement of the measurement in the oil and gas well.