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Channel-multiplexing for quasi-distributed acoustic sensing with orthogonal codes.
Optics Express
|November 23, 2021
Summary
Researchers developed new orthogonal codes to enhance quasi-distributed acoustic sensing (QDAS) performance. This advancement significantly expands sensing bandwidth in optical fiber systems for improved acoustic monitoring.
Area of Science:
- Optical Fiber Sensing
- Acoustic Sensing Technology
- Signal Processing
Background:
- Distributed Acoustic Sensing (DAS) is crucial for large-scale acoustic monitoring (e.g., hydrophones, vehicle tracking, pipeline monitoring).
- Quasi-Distributed Acoustic Sensing (QDAS) using single-mode fiber with enhanced point arrays improves signal-to-noise ratio and mitigates interference-fading issues inherent in DAS.
- Both DAS and QDAS performance are constrained by limited frequency domain resources, creating a trade-off between sensing bandwidth and distance.
Purpose of the Study:
- To overcome the limitations of finite frequency domain resources in QDAS.
- To develop a method for multiplexing QDAS channels by expanding frequency domain resources.
- To generate novel orthogonal codes for enhanced QDAS channel multiplexing with improved signal characteristics.
Main Methods:
- Modification of the iteration constraint condition for orthogonal codes.
- Development of a generation method for highly orthogonal codes with consistent suppression ratios.
- Implementation of Multiple-Input Multiple-Output (MIMO) coding technology using orthogonal probe waves within the same frequency band.
Main Results:
- Successful generation of 5 new orthogonal codes with high and consistent suppression ratios.
- Demonstration of a 5-fold sensing bandwidth expansion in QDAS over a 5.19 km fiber.
- Achieved 5 m spatial resolution and a strain noise level of 10 µε/√Hz using the new codes.
Conclusions:
- The developed orthogonal codes effectively enable QDAS channel multiplexing within the same frequency band.
- The proposed method breaks the trade-off between sensing bandwidth and distance, significantly enhancing QDAS capabilities.
- This advancement offers a promising solution for large-scale acoustic sensing applications requiring high resolution and sensitivity.
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