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Low-noise φ-OTDR employing nonlinear optical preamplification for distributed acoustic sensing.
Applied Optics
|September 14, 2023
Summary
This study introduces a new optical time domain reflectometry method to eliminate blind spots in distributed acoustic sensing. The enhanced system improves signal-to-noise ratio and measurement resolution for accurate strain monitoring.
Area of Science:
- Optoelectronics
- Fiber Optic Sensing
- Acoustic Monitoring
Background:
- Distributed acoustic sensing (DAS) using Rayleigh scattering suffers from blind spot effects and limited resolution.
- Improving signal-to-noise ratio (SNR) is crucial for accurate strain measurements in DAS.
Purpose of the Study:
- To propose and validate a phase-sensitive optical time domain reflectometry (OTDR) sensing scheme.
- To mitigate the blind spot effect in Rayleigh scattering-based DAS.
- To enhance measurement resolution and SNR in low-backscatter regions.
Main Methods:
- Development of a two-stage nonlinear optical preamplification system.
- Implementation of a phase-sensitive OTDR scheme.
- In-laboratory characterization and in-field testing on a survey well.
Main Results:
- Successfully reduced the blind spot effect by optimizing optical power distribution.
- Achieved enhanced resolution at locations with low backscatter intensity.
- Demonstrated strain noise levels below 1 nɛ at a 10 kHz sampling rate.
- Validated the system's performance in both laboratory and field environments.
Conclusions:
- The proposed phase-sensitive OTDR with nonlinear optical preamplification effectively overcomes limitations of traditional DAS.
- The system offers superior performance for distributed acoustic measurements, particularly in challenging low-backscatter scenarios.
- This advancement enables more precise and reliable strain monitoring in various applications.
