Programmable Filter for Swept-Wavelength Interferometry Signal Aliasing
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Solution Overview
Problem
Current swept-wavelength interferometry systems in oil exploration face challenges in preventing signal aliasing due to changing signal frequencies, which constrains system utility and reduces data fidelity, especially when using fixed cut-off frequency anti-aliasing filters.
Innovation Solution
A method and apparatus that utilize a programmable filter in conjunction with a variable frequency light source and detector to filter signals from fiber optic sensors deployed in a wellbore, allowing for the selection of appropriate cut-off frequencies based on the light source's frequency, thereby reducing aliasing effects and improving data fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed cut-off frequency anti-aliasing filters are used in swept-wavelength systems, then signal aliasing is prevented at a specific frequency, but data fidelity is reduced when signal frequency changes
Solution Approach 1:
The patent applies the dynamics principle by transitioning from fixed cut-off frequency filters to programmable filters that can dynamically adjust their cut-off frequency based on the instantaneous frequency of the swept-wavelength light source. This allows the filter to track and adapt to changing signal frequencies throughout the wavelength sweep, preventing aliasing at all frequency points while maintaining data fidelity.
Solution Approach 2:
The patent implements parameter changes by modifying the cut-off frequency parameter of the anti-aliasing filter to match the varying frequency of the swept-wavelength system. The programmable filter's cut-off frequency is adjusted in real-time according to the light source frequency, ensuring optimal filtering performance across the entire frequency range rather than being optimized for a single frequency point.
2Measurement precision
If sampling frequency is increased to prevent aliasing in swept-wavelength systems, then signal reconstruction accuracy is improved, but system complexity and constraints increase
Solution Approach 1:
The patent applies preliminary action by performing anti-aliasing filtering before the sampling process. By removing high-frequency components that could cause aliasing through the programmable filter, the system enables accurate signal reconstruction at lower sampling rates, thereby reducing system complexity and constraints while maintaining reconstruction accuracy.
3Reliability
If fixed frequency filtering is applied, then anti-aliasing is effective at a specific frequency, but adaptability to changing signal frequencies is lost
Solution Approach 1:
The patent resolves this contradiction by making the filter dynamics-capable through programmable control. The cut-off frequency of the filter is dynamically adjusted to follow the swept-wavelength light source frequency, ensuring that anti-aliasing effectiveness is maintained across the entire frequency range while fully adapting to changing signal frequencies throughout the wavelength sweep.
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
The solution effectively moderates constraints related to signal aliasing, enhancing data fidelity by dynamically adjusting the filtering process to match the variable frequency of the light source, ensuring accurate reconstruction of signals and improved parameter measurement accuracy.
Implementation Method 1
filtering the received signals using a programmable filter
Implementation Method 2
propagating light having variable frequency within a range of frequencies along the fiber optic cable
Implementation Method 3
receiving signals responsive to interaction of the propagated light with the plurality of sensors
Data Source
AI summary
A method, system and apparatus for obtaining a parameter of interest from a plurality of sensors in a fiber optic cable deployed in a wellbore are disclosed. Light having variable frequency within a range of frequencies is propagated along the fiber optic cable. Signals are received that are responsive to interaction of the propagated light with the plurality of sensors. The received signals are filtered using a programmable filter. The parameter of interest is obtained from the filtered signals. In one aspect, the fiber optic cable is coupled to a member deployed in the wellbore and the parameter of interest is related to the member.