Noise analysis in direct detection and coherent detection phase-sensitive optical time-domain reflectometry systems

Area of Science:

• Optics and Photonics
• Sensing Technologies
• Signal Processing

Background:

• Distributed Acoustic Sensing (DAS) systems utilize Rayleigh-backscattered light for sensing.
• Phase-sensitive Optical Time-Domain Reflectometry (ΦOTDR) is a key technique in DAS.
• Comparing direct detection and coherent detection is crucial for optimizing DAS performance.

Purpose of the Study:

• To compare noise and signal-to-noise ratio (SNR) between direct and coherent detection in fiber-based DAS.
• To evaluate the impact of photodetection filter bandwidth and selectivity on SNR.
• To provide design guidelines for high-performance time-domain DAS.

Main Methods:

• Theoretical analysis of noise and SNR in both detection schemes.
• Experimental validation of the theoretical models.
• Dynamic analysis of Rayleigh-backscattered light in ΦOTDR systems.

Main Results:

• For narrow bandwidth photodetection filters, SNR performance is comparable between direct and coherent detection.
• Coherent detection demonstrates superior SNR performance when using filters with poor selectivity.
• The study quantifies the trade-offs in SNR based on filter characteristics.

Conclusions:

• Photodetection filter selectivity significantly impacts DAS performance.
• Coherent detection is advantageous in scenarios with less selective filtering.
• Findings offer critical insights for designing advanced time-domain DAS systems.