Non-uniform Sampling for Interferometric Sensor Dynamic Range
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Solution Overview
Problem
Conventional demodulation techniques for interferometric sensors require high computational resources and are inefficient in handling high fringe rates, especially in applications like ocean bottom seismic surveys where large dynamic ranges are needed, due to the high bandwidth of fringe signals which exceeds the sensor signal bandwidth.
Innovation Solution
The method involves transmitting non-uniform sequences of optical signals to interferometric sensors and sampling interference signals with non-uniform intervals, allowing for the reconstruction of fringe phasors and extraction of sensor parameters, which reduces the bandwidth of the fringe signal and thereby reduces computational demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional demodulation techniques are used to handle high fringe rates, then the sensor signal can be demodulated, but the bandwidth of the fringe signal becomes excessively large, requiring considerable computational resources
Solution Approach 1:
The patent changes the temporal sampling parameters from uniform to non-uniform intervals. By using non-uniform sampling, the system captures the essential signal characteristics while reducing the overall data rate and bandwidth requirements for fringe signal processing, thereby lowering computational resource demands while maintaining demodulation accuracy
Solution Approach 2:
The patent employs periodic modulation of the interrogation signal with a subcarrier frequency. This periodic action allows the fringe signal to be shifted to a higher frequency band, enabling efficient sampling and processing by concentrating the signal energy at specific frequencies, thus reducing the bandwidth requirements compared to direct demodulation of the baseband fringe signal
2Ease of operation
If uniform sampling is used for fringe signal processing, then the sampling process is simple, but the bandwidth of the fringe signal exceeds the sensor signal bandwidth, making demodulation inefficient
Solution Approach 1:
The patent transforms the sampling regime from uniform to non-uniform by introducing variable time intervals between samples. This parameter change allows the system to adapt the sampling rate to the instantaneous fringe rate, capturing critical signal features during high-rate periods while reducing sampling during low-rate periods, thereby improving processing efficiency without sacrificing measurement capability
Solution Approach 2:
The patent introduces dynamic adaptation in the sampling process by adjusting sampling intervals based on the instantaneous frequency content of the fringe signal. This dynamic approach allows the system to optimize the trade-off between sampling simplicity and processing efficiency, maintaining ease of operation while significantly improving overall signal processing productivity through adaptive resource allocation
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 the bandwidth of the fringe signal, enabling a large dynamic range in demodulated sensor phases and minimizing computational resource allocation, thus enhancing the efficiency of signal processing in interferometric sensors.
Implementation Method 1
extracting the phase of the interference (optically detected as a fringe signal) between the interrogation signal that has propagated the two sensor pathways
Data Source
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AI summary
Methods and apparatus for interrogating optical sensors with high slew rates using non-uniform sampling are provided. The transmission of optical signals in a non-uniform pattern is employed to allow for demodulation of fringe rates exceeding the commonly understood Nyquist frequency limit given as one half of the mean sampling frequency. By monitoring the time dependent fringe frequency and assuming that the fringe frequency has a limited bandwidth, only a limited bandwidth smaller than the Nyquist bandwidth around the instantaneous fringe frequency needs to be reconstructed at any time.