Optical Fiber DAS Measurand Separation Using Multi-Frequency Sensing
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Solution Overview
Problem
Conventional Distributed Acoustic Sensing (DAS) systems struggle to discriminate between multiple measurands such as strain, temperature, and pressure in optical fibers due to non-vanishing sensitivity, leading to cross-sensitivity errors.
Innovation Solution
The proposed solution involves performing multiple DAS measurements using different optical frequencies and a single spatial fiber mode to exploit the difference in optical frequency dependence of sensitivities, allowing discrimination of measurands through techniques like matched filtering and phase differentiation, and using a sensitivity matrix to determine the measurand vector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DAS measurements are performed using a single optical frequency, then the measurement system is simple, but multiple measurands (strain, temperature, pressure) cannot be discriminated due to cross-sensitivity errors
Solution Approach 1:
The patent applies parameter changes by performing DAS measurements at multiple different optical frequencies. Each frequency provides a measurement signal with different sensitivity characteristics to the various measurands (strain, temperature, pressure). By changing the optical frequency parameter and collecting measurements across multiple frequencies, the system can mathematically discriminate between different measurands and eliminate cross-sensitivity errors, thereby improving measurement precision without requiring additional physical sensors.
2Measurement precision
If multiple DAS measurements are performed using different optical frequencies, then cross-sensitivity errors are reduced, but the measurement time and processing complexity increase
Solution Approach 1:
The patent implements periodic action by systematically cycling through multiple optical frequencies in a structured measurement sequence. The system performs DAS measurements at each frequency in turn, collecting a set of measurement signals that collectively provide the information needed to discriminate measurands. This periodic approach to frequency sampling allows for efficient data collection and mathematical processing to achieve accurate measurand determination while managing measurement time.
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 enables precise discrimination of measurands like strain, temperature, and pressure with reduced cross-sensitivity errors, providing more accurate measurements.
Implementation Method 1
backscattering may result from elastic scatterers in the optical fiber, such as, e.g., at least one of Rayleigh scattering
Implementation Method 2
backscattering may result from inelastic scattering, such as, e.g., at least one of Raman based distributed temperature sensing (DTS)
Implementation Method 3
backscattering may result from inelastic scattering, such as, e.g., at least one of Brillouin based distributed sensing (e.g. BOTDR)
Data Source
AI summary
An apparatus for processing data associated with an optical fiber, the apparatus comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to: perform a plurality of measurements applying a distributed acoustic sensing technique to the optical fiber to obtain a plurality of measurement signals, each of the plurality of measurements using a different optical frequency and a single spatial fiber mode of the optical fiber, determine at least one measurand of a plurality of measurands associated with the optical fiber based on the plurality of measurement signals.