Phase Measurement in Distributed Acoustic Sensing Using Wavelength-Multiplexed Vector Alignment
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Solution Overview
Problem
In distributed acoustic sensing (DAS) systems, noise from measuring devices, such as heat noise and shot noise, affects the accuracy of phase measurement of scattered light, leading to increased uncertainty and false recognition of physical forces applied to optical fibers, especially when the intensity of scattered light decreases due to fading.
Innovation Solution
A phase measurement method and signal processing device that utilize wavelength-multiplexed pulse light to align scattered light vectors in a two-dimensional plane, calculating the phase based on the arithmetic average of vectors from different wavelengths to reduce noise influence without increasing the peak intensity of the incident light pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the intensity of incident light pulse is increased to improve phase measurement precision, then measurement precision is improved, but non-linear effects occur in the optical fiber
Solution Approach 1:
The patent combines scattered light vectors from multiple wavelengths into a single synthesized vector through coherent addition. By merging the information from N different wavelengths, the measurement precision is improved without increasing the peak intensity of individual pulses, thus avoiding non-linear effects while achieving better phase measurement accuracy.
Solution Approach 2:
The patent changes the parameter of wavelength diversity by using N different wavelengths instead of a single wavelength. This parameter change allows the system to achieve improved measurement precision through multi-wavelength vector synthesis without requiring higher peak intensity, thereby avoiding non-linear effects in the optical fiber.
2Measurement precision
If wavelength-multiplexed pulse light is used to reduce noise influence, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex hardware-based phase extraction mechanisms with software-based signal processing. By using digital signal processing techniques to synthesize vectors from multiple wavelengths and calculate phases, the system achieves improved measurement precision while managing device complexity through computational methods rather than additional optical components.
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
This approach effectively reduces noise influence in phase measurement, enhancing the accuracy of vibration detection by minimizing the impact of fading and maintaining measurement precision without increasing the peak intensity of the incident light pulse.
Implementation Method 1
A method called distributed acoustic sensing (DAS) that causes test pulse light to be incident on a measurement target optical fiber and detects backscattered light due to Rayleigh scattering
Data Source
AI summary
It is intended to provide a phase measurement method and a signal processing device that are capable of reducing influence of noise of a measuring device without increasing the peak intensity of an incident light pulse when measuring the phase of scattered light in DAS-P.A phase measurement method according to the present invention causes wavelength-multiplexed pulse light to be incident on a measurement target optical fiber, produces a scattered light vector obtained by plotting scattered light from the measurement target optical fiber for each wavelength onto a two-dimensional plane having the in-phase component thereof on the horizontal axis and the orthogonal component thereof on the vertical axis, rotates the produced scattered light vector for each wavelength at each place in the measurement target optical fiber to align the directions of the vectors, generates a new vector by calculating the arithmetic average of the vectors having the aligned directions, and calculates the phase by using the values of the in-phase and orthogonal components of the generated new vector.