Optical Time Delay Interferometry Noise Management
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Solution Overview
Problem
Fiber optic sensing systems face challenges in managing noise, particularly in reducing acoustic signals that contribute to the signal noise floor, which hampers the detection and demodulation of acoustic pressure waves in distributed acoustic sensing applications such as remote downhole monitoring of oil wells and physical security.
Innovation Solution
A distributed fiber optic sensing system with an integrated fiber optic interrogator and embedded controller, utilizing time-domain reflectometry to mitigate acoustic noise and enhance noise floor management, allowing for longer sensing lengths and improved detection of acoustic wave signals up to 40.0 km with increased flexibility and utility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fiber optic sensing systems are used for distributed acoustic sensing, then detection capability is improved, but acoustic noise interference increases the signal noise floor
Solution Approach 1:
The patent extracts and removes acoustic noise components from the received optical signal through signal processing techniques. The system separates the desired acoustic wave signals from the noise floor by identifying and eliminating noise characteristics, thereby improving the signal-to-noise ratio and enabling detection over extended fiber lengths.
Solution Approach 2:
The patent introduces intermediate signal processing stages including reference signal generation, correlation processing, and filtering mechanisms. These intermediary components act as mediators between the raw optical signal and the final detected acoustic waves, enabling noise mitigation while preserving the desired signal characteristics.
2Length of stationary object
If sensing length is extended to 40.0 km, then coverage area is improved, but noise accumulation increases
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors the signal quality and noise levels along the fiber span. Based on this feedback, the signal processing algorithms dynamically adjust filtering parameters and processing gains to compensate for noise accumulation over extended sensing lengths, enabling stable operation at 40.0 km.
Solution Approach 2:
The patent applies preliminary noise characterization and mitigation strategies before the actual acoustic sensing measurement. The system performs reference measurements and establishes noise profiles in advance, then uses this pre-acquired information to subtract or filter noise from the subsequent sensing measurements, enabling extended range operation.
3Measurement precision
If acoustic noise is reduced, then signal noise floor is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex physical noise isolation mechanisms with computational signal processing approaches. Instead of using elaborate mechanical damping, vibration isolation, or acoustic shielding hardware, the system uses digital signal processing algorithms to filter and remove noise from the optical signal, achieving noise reduction with simpler physical hardware but more computational processing.
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 system effectively reduces noise interference, enabling the detection and demodulation of acoustic wave signals over extended lengths, thereby enhancing the utility and flexibility of fiber optic sensing systems for various applications, including remote monitoring and security.
Implementation Method 1
utilizing time-domain reflectometry to mitigate acoustic noise and enhance noise floor management
Implementation Method 2
light is sent through an optical fiber and the returning backscattered light is analyzed
Implementation Method 3
Phase differencing the reflected signal with a reference signal, minute changes can be detected; these relate directly to the event that is causing the laser signals to be reflected
Implementation Method 4
acoustic pressure waves in the vicinity of a fiber cable will impart micro strains on the fiber. These micro strains are proportional to the acoustic pressure waves, essentially imparting the frequency of the acoustic pressure wave into the back reflected signal
Data Source
AI summary
An integrated fiber interferometry interrogator for generating superimposed waves is disclosed. The system is optimized for efficiency and vibration attenuation. The system comprises an optical light source for generating a first signal, a first signal splitter which splits the first signal into a reference signal and an interrogation signal, optical modulators for modulating the signals, a fiber coupler connected to a fiber under test, an isolator, a circulator with a plurality of connections for directing the signals, a signal mixer for mixing the signals into superimposed waves, and photo diodes for receiving the superimposed waves.