Optical Fiber DAS IQ Demodulation for Phase Drift Correction
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Solution Overview
Problem
Optical fiber Distributed Acoustic Sensing (DAS) data demodulation is affected by phase drift due to nonlinear effects and frequency drift, leading to inaccurate phase information and high noise levels, which existing methods fail to adequately address.
Innovation Solution
A method for global phase IQ Demodulation of optical fiber DAS data involving multiple correction operations: interrogation pulse phase correction, initial phase correction at the receiving point, linear phase correction with respect to the interrogation pulse, and linear phase correction at the receiving point, followed by phase unwrapping and de-near DC component processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase differencing and local averaging within the gauge length are used to overcome nonlinear effects, then signal-to-noise ratio is improved, but low-wavenumber wavefield information is lost and noise level cannot be reduced to ideal level
Solution Approach 1:
The patent segments the phase correction process into multiple distinct stages: interrogation pulse phase correction, initial phase correction at receiving point, linear phase correction with respect to interrogation pulse, and linear phase correction at receiving point. Each stage addresses specific phase error components separately, preventing information loss that occurs when using a single aggregated correction method.
Solution Approach 2:
The patent applies preliminary phase correction operations before final phase unwrapping and de-noising processing. By correcting phase errors at multiple stages in advance, the method preserves low-wavenumber wavefield information that would otherwise be lost during subsequent processing.
2Measurement precision
If phase differencing and local averaging are applied to improve signal-to-noise ratio, then nonlinear effects are overcome, but noise level cannot be reduced to ideal level
Solution Approach 1:
The patent divides noise reduction into separate stages: initial phase correction removes systematic phase errors, followed by linear phase correction that addresses remaining linear drift components. This segmented approach achieves ideal noise level reduction that single-stage methods cannot accomplish.
Solution Approach 2:
The patent implements iterative feedback processing where phase correction results are fed back through multiple correction stages. Each stage uses the output of previous stages as input, continuously refining the signal to achieve optimal noise reduction and reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method significantly improves the accuracy of optical fiber DAS data by mitigating the effects of nonlinear phase shifts and noise, providing reliable data for subsequent analysis.
Implementation Method 1
The optical fiber DAS technology is a detection technology based on Rayleigh backscattering (RBS) effect of optical fiber
Implementation Method 2
The receiver includes at least one fiber optic coupler that receives backscattered light and that produces optical interferometry signals from the backscattered light
Implementation Method 3
The receiver also includes photo-detectors that produce an electrical signal for each of said optical interferometry signals
Data Source
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AI summary
A global phase quadrature demodulation method and apparatus for optical fiber sensing data. The method comprises : acquiring initial optical fiber sensing IQ data; determining a corresponding direct phase value on the basis of the initial optical fiber sensing IQ data, and executing a light source phase correction operation on a direct phase to obtain first processed data; executing a reception point initial phase correction operation on the first processed data to obtain second processed data; performing a light source linear phase correction operation on the second processed data to obtain third processed data; executing a reception point linear phase correction operation on the third processed data to obtain fourth processed data; and performing phase unwrapping processing and near-direct current component removal processing on the fourth processed data to obtain global phase demodulated data. According to the present solution, various influence factors of initial optical fiber sensing data are analyzed, a corresponding data optimization processing method is employed, the problems existing during the acquisition process of optical fiber sensing data are solved, and the accuracy of the optical fiber sensing data is improved.