Optical Interferometer Sensing for Fast Distributed Acoustic Detection
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Solution Overview
Problem
Current distributed optical fibre sensors have slow response times and limited sensitivity, making them unsuitable for applications requiring fast and high-resolution measurements, such as acoustic sensing, while multiplexed point sensors lack the ability for full coverage and are bulky and expensive.
Innovation Solution
A novel interferometer apparatus using non-reciprocal devices like Faraday rotator mirrors and optical circulators allows for fast and sensitive measurement of phase, frequency, and amplitude of light along an optical fibre, enabling detection of acoustic perturbations with fine spatial resolution, applicable to both distributed and multiplexed sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If distributed optical fibre sensors are used, then continuous sensing along the entire length of fibre is achieved, but the response time is slow (seconds to hours)
Solution Approach 1:
The patent changes the measurement parameter from intensity-based (slow) to phase-based (fast) detection. By using phase modulation and interferometric detection, the system achieves fast response times while maintaining distributed sensing capability along the entire fibre length.
Solution Approach 2:
The patent replaces the traditional intensity-based detection mechanism with a phase-based interferometric detection system. This substitution enables faster response by using phase modulation and demodulation techniques rather than relying on slow intensity measurements.
2Ease of operation
If distributed optical fibre sensors are used, then flexibility and simplicity are achieved, but sensitivity and measurement speed are limited
Solution Approach 1:
The patent introduces phase modulation as an intermediary mechanism to enhance sensitivity. By modulating the optical phase and using interferometric detection, the system achieves high sensitivity measurements while maintaining the simplicity of distributed fibre sensing architecture.
3Measurement precision
If multiplexed point sensors are used, then fast measurements with high sensitivity are achieved, but full coverage is not possible and the system is bulky and expensive
Solution Approach 1:
The patent creates a universal sensing system that combines the advantages of both distributed and point sensors. The phase-based interferometric detection method can detect acoustic perturbations at any location along the fibre, providing full coverage like distributed sensors while achieving fast response and high sensitivity like point sensors, all using standard optical fibre infrastructure.
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 solution dramatically enhances the speed and sensitivity of acoustic sensing, enabling applications like monitoring oil and gas wells, seismic imaging, and security, with the ability to detect acoustic perturbations along the fibre length with high spatial resolution and dynamic range.
Implementation Method 1
an optical interferometer apparatus which provides multiple path differences between optical signals and provides interference signals between different optical paths with fixed and/or variable phase shifts
Implementation Method 2
The optical interferometer may use optical fibre components such as an m × m fused optical fibre coupler that is connected to an optical fibre circulator at one of its ports; Faraday-rotator mirrors that reflect and, at the same time, provide polarisation compensation for the light propagating through the different paths of the interferometer
Data Source
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AI summary
The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.