A Weak Reflection Bragg Grating Accelerometer and Its Sensing Method

Abstract

The invention discloses a weak-reflection Bragg grating accelerometer and a sensing method thereof. First, second and third gratings which are distributed at equal intervals are graved in a polarization-maintaining sensing optical fiber; two pulses which are mutually independent in a time domain return after sequentially going through the first, second and third gratings to generate two interference pulses carrying outside vibration information, phase of the interference pulses carrying the outside vibration information is demodulated and then reduced so as to acquire outside vibration information inhibiting common-mode noise, and phase difference is proportional to outside vibration signals. Noise suppression level is elevated, common-mode noise introduced by a laser device and an acoustic optical modulator can be eliminated, environment noise introduced to the accelerometer itself by perturbation of outside environment can be eliminated, phase sensitivity is improved, transverse crosstalk is inhibited, cost of a sensing system is saved while size of the same is reduced, and this advantage is obviously demonstrated especially in a quasi-distributed multi-motif sensing network.

Description

technical field [0001] The invention relates to an optical fiber accelerometer, in particular to a weak reflection Bragg grating accelerometer and a sensing method thereof. Background technique [0002] Fiber optic accelerometers have been widely used in sound and vibration measurement in industrial fields, such as submarine oil and gas reservoir monitoring, microseismic monitoring, and downhole monitoring. Compared with traditional electronic sensors, fiber optic accelerometers have the advantages of high sensitivity, anti-electromagnetic interference, and easy to form distributed sensor networks. Among all types of fiber optic accelerometers, the interferometric accelerometer based on the conformable cylindrical structure is the mainstream application. By coiling the fiber around the elastic cylinder, when the external vibration causes the deformation of the elastic cylinder, the optical fiber wound around the elastic cylinder will Expansion or compression is produced, an...

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Problems solved by technology

[0004] The traditional method of using a reference accelerometer to eliminate common-mode noise has several disadvantages: (1) The common-mode noise generated by the active optical device can be eliminated by phase subtraction, but it cannot eliminate the noise caused by the external environment acting on the sensing accelerometer. (2) The reference accelerometer still has a certain sensitivity, that is, it can still perceive certain external vibration information, so while eliminating the common mode noise, it will still filter out some useful external vibration signals; (3) The reference accelerometer The presence increases the size and cost of the sensing system

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