This paper aims to solve the problem of the fiber optic cable sensitivity measurement. A fiber optic cable sensitivity measurement method is proposed based on distributed acoustic sensor (DAS) system, and an experimental device is implemented. Five different optical cables are connected to the DAS system, and the acoustic pressure sensitivity of different optical cables at different frequencies is measured through the DAS system. The results show that the cable G654 has the maximum sensitivity of -148.84 dB(rad/μPa) at 120 Hz, GYTA53T has the maximum sensitivity of -160.68 dB(rad/μPa) at 140 Hz, and G657A2 has the maximum sensitivity of -166.07 dB(rad/μPa) at 160 Hz.
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.
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 corrugated diaphragm is developed. The measured medium is isolated from the fiber F-P cavity by corrugated diaphragm which can transmit pressure simultaneously. The probe of the sensor is fabricated by hydrogen and oxygen flame thermal bonding in high temperature technique, and the change of the senor’s cavity length is compensated in temperature changing with cascading fiber bragg grating, and 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 0~69MPa, the repeatability is 0.01% F·S, the hysteresis is less than 0.01% F·S, the long term stability is less than 0.02MPa/y, and the sensor can satisfy the requirement of the measurement in the oil and gas well.
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