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Sensors 2018, 18(12), 4279; https://doi.org/10.3390/s18124279

Reference Phase Stabilizer for Distributed Underwater Sonar Systems

The Institute of Marine Electronic and Intelligent System, Ocean College, Zhejiang University, Zhoushan 316021, China
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Received: 30 September 2018 / Revised: 12 November 2018 / Accepted: 30 November 2018 / Published: 5 December 2018
(This article belongs to the Special Issue Underwater Sensing, Communication, Networking and Systems)
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Abstract

An optical fiber is a promising approach for data and clock transmission in distributed underwater sonar systems. However, synchronization is a critical challenge in distributed sonar systems, which mandates accurate clock synchronization down to a sub degree. Potential phase misalignment is caused by fiber length variations. In this paper, we propose a fiber-based phase stabilizer method to achieve accurate clock synchronization among sensor nodes. We use fiber-based feedback loop between sensor nodes and central station unit to monitor phase variations. Subsequently, we leverage phase shifters symmetrically arranged on the forward lane and feedback lane to compensate real-time phase variation and maintain high-precision synchronization. Besides, an ambiguity eliminator circuit is designed to remove the clock’s cyclic ambiguity. Both analysis and experimental results suggest that the proposed phase stabilizer can achieve 10 MHz reference clock synchronization within 0.4 degree. We also analyze the impact of the reference clock’s phase error on the system range detection accuracy, which indicates that the proposed phase stabilizer can greatly improve detection accuracy of sonar systems. View Full-Text
Keywords: distributed sonar systems; reference dissemination; phase synchronization distributed sonar systems; reference dissemination; phase synchronization
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Yang, L.; Dang, R.; Song, C.; Xu, Z. Reference Phase Stabilizer for Distributed Underwater Sonar Systems. Sensors 2018, 18, 4279.

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