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Revolutionizing Underwater Sensor Performance: Tackling Rayleigh Scattering Challenges by Pseudo Random Noise.
Qihao Hu1, Fan Shang1, Lina Ma1
1College of Meteorology and Oceanography, National University of Defense Technology, Changsha, Hunan, 410073, China.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|December 5, 2024
Summary
Rayleigh scattering significantly impacts fiber optic interferometric sensors (FOIS) even with shorter fiber lengths due to Rayleigh backward scattering (RBS) interactions. A novel pseudorandom noise (PRN) phase modulation method effectively suppresses this background noise, enhancing underwater sensing capabilities.
Area of Science:
- Optical Physics
- Fiber Optic Sensing
- Signal Processing
Background:
- Rayleigh scattering traditionally considered negligible in fiber sensing below 10 km.
- Rayleigh backward scattering (RBS) interaction with returning interference signals in FOIS is often overlooked.
- Existing FOIS systems may be limited by unaddressed background noise.
Purpose of the Study:
- To theoretically and experimentally demonstrate the impact of RBS on FOIS performance with shorter leading fibers.
- To elucidate the interaction mechanism between RBS and FOIS interference signals.
- To develop and validate a novel method for mitigating RBS-induced noise in FOIS.
Main Methods:
- Development of a conceptual framework to analyze RBS-FOIS interference.
- Investigation of laser pulse characteristics (monochromacity, self-correction) influence on coherent superposition.
- Proposal and implementation of a phase modulation method using pseudorandom noise (PRN) codes.
- Experimental validation of the PRN method in a 3.3 km FOIS system.
Main Results:
- Demonstrated that RBS significantly affects FOIS performance even with hundreds of meters of leading fiber.
- Identified laser pulse self-correction as a factor influencing coherent superposition.
- Achieved a 21.3 dB suppression of background phase noise using the PRN phase modulation method.
- Preserved high laser monochromacity while mitigating RBS stacking.
Conclusions:
- Rayleigh scattering is a critical factor in FOIS performance, irrespective of fiber length, due to RBS.
- The proposed PRN phase modulation technique effectively suppresses coherent RBS stacking.
- This research enhances understanding of Rayleigh scattering in leading fibers, improving underwater sensing applications.
