Dynamic Range Suppression in Distributed Acoustic Sensing
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Solution Overview
Problem
Distributed acoustic sensing using coherent optical time-domain reflectometry faces challenges with extreme dynamic range variations in Rayleigh backscatter amplitudes due to fiber attenuation, leading to interference and potential damage to photodetectors, as well as susceptibility to noise at varying signal power levels.
Innovation Solution
Implementing a feedback loop with optical and electrical elements to invert and pre-compensate the optical signal or using nonlinear elements in the electrical domain to reduce amplitude dynamic range before sampling, thereby minimizing dynamic range variations and preventing signal damage and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coherent optical time domain reflectometry is used for distributed acoustic sensing, then sensing capability is improved, but extreme dynamic range variations cause interference and potential damage to photodetectors
Solution Approach 1:
The patent applies preliminary action by pre-compensating the optical signal with an inverted amplitude profile before detection. The system calculates the expected amplitude variation due to fiber attenuation and applies a compensating gain profile in advance, so that when the signal reaches the photodetector, the dynamic range is already suppressed and不会再 cause interference or damage.
Solution Approach 2:
The patent implements feedback by continuously monitoring the received optical signal amplitude and using this information to adjust the pre-compensation profile. The system measures the actual amplitude variations, compares them with the expected profile, and refines the compensation parameters to optimize dynamic range suppression while maintaining sensing accuracy.
2Measurement precision
If coherent optical time domain reflectometry is used for distributed acoustic sensing, then sensing capability is improved, but signal power variations cause susceptibility to noise
Solution Approach 1:
The patent applies preliminary action by pre-amplifying weak signals and attenuating strong signals before they reach the detection stage. By applying a gain profile that is inverted relative to the expected amplitude decay, the system equalizes the signal power across different fiber segments, ensuring that all signals are received at optimal power levels for noise-resistant detection.
Solution Approach 2:
The patent changes the amplitude parameter of the optical signal through dynamic gain adjustment. The system varies the gain parameter as a function of position along the fiber, creating a position-dependent amplification profile that compensates for attenuation and maintains consistent signal-to-noise ratio throughout the sensing range.
3Manufacturing precision
If dynamic range suppression is implemented using feedback loop with optical and electrical elements, then amplitude dynamic range is minimized, but system complexity increases
Solution Approach 1:
The patent introduces an intermediary optical component (such as an optical amplifier with controlled gain or an optical attenuator) that acts as a mediator between the fiber under test and the photodetector. This intermediary element applies the pre-compensation in the optical domain before detection, simplifying the overall system architecture by handling dynamic range suppression optically rather than requiring complex electronic processing of high-dynamic-range signals.
4Manufacturing precision
If nonlinear element is used in electrical domain to reduce amplitude dynamic range, then dynamic range suppression is achieved, but additional electrical processing complexity is introduced
Solution Approach 1:
The patent replaces complex electronic dynamic range compression circuits with a simpler optical pre-compensation approach. By performing the dynamic range suppression in the optical domain using gain-controlled amplifiers or variable attenuators, the system avoids the need for complex nonlinear electrical processing, ADC dynamic range management, and digital signal processing algorithms.
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 proposed solution effectively suppresses dynamic range variations, preventing interference and damage to photodetectors, and improving signal-to-noise ratios by stabilizing the optical signal power, thus enhancing the reliability and accuracy of distributed acoustic sensing systems.
Implementation Method 1
distributed acoustic sensing using coherent detection of Rayleigh backscatter
Implementation Method 2
coherent detection of Rayleigh backscatter
Implementation Method 3
after coherent detection
Data Source
AI summary
Aspects of the present disclosure describe improved distributed acoustic sensing using dynamic range suppression of optical time domain reflectometry either by using a feedback loop comprising optical and electrical elements or using a nonlinear element in the electrical domain after coherent detection. When using a feedback loop, the amplitude of the periodic waveform of coherent OTDR can be inverted. This allows optical pre-compensation of the received optical signal before coherent detection with the goal of minimizing amplitude dynamic range. Alternatively, a nonlinear element in the electrical domain can reduce amplitude dynamic range before sampling by analog-to-digital converters (ADC).