Phase Based Sensing Overscaling Correction
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Solution Overview
Problem
Fibre optic sensors used in seismic surveying experience signal distortion and failure due to overscaling, particularly with high-amplitude inputs like the direct arrival of the incident pulse, leading to phase-based sensed information becoming distorted and causing demodulation failures.
Innovation Solution
A method involving the use of a pulse train with delayed and undelayed pulses to determine the rate of change of phase, allowing for low-sensitivity derivative measurements that are less affected by overscaling, and combining these with direct phase measurements to reconstruct the sensed parameter, while employing adaptive systems to switch between direct and derivative measurements based on amplitude thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-based sensing is used to achieve high sensitivity measurements, then measurement precision is improved, but signal distortion occurs due to overscaling with high-amplitude inputs
Solution Approach 1:
The patent changes the measurement parameter from direct phase measurement to measurement of the derivative of phase with respect to time. This parameter transformation allows the system to measure high-amplitude signals without the overscaling distortion that affects direct phase measurements, while still maintaining measurement precision through the derivative relationship.
Solution Approach 2:
Instead of directly measuring the phase signal that becomes distorted at high amplitudes, the patent measures the derivative of the phase signal. This inverted approach of measuring the rate of change rather than the absolute value allows accurate measurement of high-amplitude inputs by avoiding the nonlinear distortion that occurs in direct phase-based sensing.
2Quantity of substance
If direct phase measurement is used to capture high-amplitude signals, then signal amplitude is recorded, but phase information becomes distorted and demodulation fails
Solution Approach 1:
The patent transforms the measurement from direct phase to derivative of phase, enabling the system to capture high-amplitude signal information without losing phase data. The derivative measurement remains linear even when the original phase signal would overscale, thus preserving phase information that can be used to reconstruct the original signal.
Solution Approach 2:
The system uses the derivative measurement as feedback to reconstruct the original phase signal. By integrating the derivative information and using it to correct or reconstruct the phase data, the system recovers phase information that would otherwise be lost due to overscaling in direct measurement approaches.
3Reliability
If derivative measurement is used to avoid overscaling, then signal distortion is reduced, but signal-to-noise ratio decreases
Solution Approach 1:
The patent combines both direct phase measurement and derivative phase measurement into a unified system. By merging these two measurement approaches, the system can use the derivative measurement to avoid overscaling distortion while simultaneously using the direct measurement to maintain signal-to-noise ratio, achieving both goals through combination rather than choosing one over the other.
Solution Approach 2:
The patent creates a composite measurement approach that integrates direct phase sensing and derivative phase sensing. This composite measurement system leverages the advantages of both methods: the direct measurement provides high signal-to-noise ratio while the derivative measurement prevents overscaling distortion, resulting in a measurement system that achieves both reliability and precision.
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 reduces signal distortion and improves signal-to-noise ratio (SNR) by using derivative measurements to correct for overscaling effects, enabling accurate recording of high-amplitude inputs without phase distortion, thereby enhancing the reliability of seismic data acquisition.
Implementation Method 1
interfering a pulse representing the state of the transducer at a first time, and a pulse representing the state of the transducer at a second time, the two pulses having undergone the same optical path at different times
Data Source
Figure 1
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AI summary
Interrogation of a phase based transducer is performed by comparing the state of the transducer at two points in time to determine the rate of change with time of the measurand represented as a phase change. The rate of change, or derivative of the phase change typically has a much smaller amplitude than the signal itself, and the derivative measurement can therefore be thought of as a low sensitivity measurement to be used instead of or in combination with the normal signal measurement having higher sensitivity. In this way, large amplitude signals which might otherwise be subject to overscaling effects can be measured more effectively. For a signal with the majority of its energy centred at approximately 800Hz, for example, the derivative of that signal will typically be attenuated by 60dB with a period between the two measurement times of 200ns.