Orthogonal phase-maintained three-wavelength demodulation-type optical fiber acoustic sensing system and method

Abstract

The invention belongs to the technical field of optical fiber sensing, and discloses an orthogonal phase-maintained three-wavelength demodulation-type optical fiber acoustic sensing system and method.A wavelength control and synchronous sampling module realizes synchronous acquisition and transmission of laser output wavelength drive and photodetector data. A wide tunable laser realizes a wavelength switching speed in the order of nanoseconds, an interference spectrum of a Fabry-Perot interference optical fiber acoustic sensor is obtained through wavelength linear scanning, an initial cavitylength is calculated, and three orthogonal wavelengths are further selected for fast dynamic cavity length demodulation. The DC component of the real-time cavity length is used to calculate the amountof orthogonal phase deviation, three-wavelength orthogonal phase lock is realized, and the problem that the existing three-wavelength demodulation technology cannot adapt to large amplitude cavity length change to result in orthogonal phase deviation can thus be solved. Thus, the defects of the existing optical fiber acoustic sensing system can be solved, and by adopting the three-wavelength demodulation mode, high-speed, large-dynamic range, high-resolution, and high-stability demodulation can be realized.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and for the first time proposes a quadrature phase-maintained common optical path three-wavelength cavity length demodulation scheme to realize high-speed, high-resolution, and high-stability cavity length demodulation of optical fiber acoustic sensors. Background technique [0002] High-performance dynamic sensing of acoustic signals has been widely used in nondestructive testing, photoacoustic imaging, and structural condition monitoring. Due to its compact structure, high sensitivity, anti-electromagnetic interference, remote monitoring and multiplexing capabilities, the interferometric fiber-optic acoustic sensor is an acoustic sensing technology with great potential, especially in extreme temperatures, strong electromagnetic interference, etc. And other usage scenarios where traditional electro-acoustic sensors cannot be used. Usually based on four basic structures: fiber Mach...

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Problems solved by technology

[0003] However, the premise of the three-wavelength quadrature phase demodulation method is to meet the quadrature phase condition. When the cavity length of the Fabry–Perot acoustic sensor changes greatly due to changes in the external environment temperature or pressure, the original quadrature phase The conditions will not be satisfied, and the data obtained by continuing to demodulate in the original way will have non-negligible errors

In practical engineering applications, due to the harsh environment or the need for long-term monitoring, there is a high possibility of large cavity length changes, which brings great challenges to the effectiveness of the three-wavelength quadrature demodulation method

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