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摘要:
相比于传统基于声纳、光缆的水下频率传递技术,水下激光频率传递技术具有更高的灵活性。本文首先介绍了水下激光频率传递技术的背景与意义,同时简要展示了国内外科研机构在水下激光频率传递方面的成果。然后,从理论上描述了水下链路特性的时域和频域特性,前者基于水体折射率微扰,后者基于柯尔莫哥洛夫大气湍流模型。接着,重点报道了电子科技大学在该领域的研究进展,包括电学相位补偿技术、光学相位补偿技术和多址频率分发技术。最后总结了这三类水下频率传递实验,对课题组在水下激光频率传递方面将要进行的工作进行了展望。作为具有较大潜力的水下频率传递技术,未来水下激光频率传递技术将在相关应用中发挥重要作用。
Abstract:Inspired by underwater wireless optical communication, laser-based underwater frequency transfer technology extends frequency transfer and dissemination from fiber links and free-space links to underwater links and shows greater potential for applications. Compared with traditional underwater frequency transfer technologies (sonar, fiber links), laser-based underwater frequency transfer technology is more flexible and avoids the multipath effect and high latency. In the future, this technology is expected to contribute to the applications of underwater navigation and sensing, distributed observation networks, tracking and positioning systems, etc. This paper first introduces the background and significance of the underwater laser-based frequency transfer technique, and briefly shows the achievements of domestic and foreign scientific research institutions in underwater laser-based frequency transfer. Next, the paper presents the time domain and frequency domain descriptions of underwater link properties, in which the former is based on the refractive index perturbation of the water column and the latter is based on the Kolmogorov atmospheric turbulence model. Then, the research results of the University of Electronic Science and Technology in laser-based underwater frequency transfer are reported, including the electrical phase compensation technique, the optical phase compensation technique, and the multiple-access frequency dissemination technique. Finally, the three laser-based underwater frequency transfer experiments are summarized, and the future works of our group in laser-based underwater frequency transfer have been prospected. As a promising underwater frequency transfer technology, laser-based underwater frequency transfer technology will play a crucial role in relevant applications in the future.
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图 4 定时抖动曲线[49]。(a) 链路长度为3 m;(b) 链路长度为6 m;(c) 链路长度为9 m;(d) 测量本底
Figure 4. Timing fluctuation curves [49]. (a) Timing fluctuation of the underwater transmission link of 3 m; (b) Timing fluctuation of the underwater transmission link of 6 m; (c) Timing fluctuation of the underwater transmission link of 9 m; (d) Measurement floor for a short link
图 5 基于电学相位补偿技术的水下激光频率传递[50]。PS: 移相器;CW: 连续波;PD:光电探测器;PI:比例-积分控制器;HM:半反射镜
Figure 5. Laser-based underwater frequency transfer based on electronic phase compensation technique [50]. PS: phase shifter; CW: continuous wave; PD: photodetector; PI: proportion–integration controller; HM: half reflected mirror
图 6 实验结果[50]。(a) 定时抖动曲线:(i)-无补偿;(ii)-有补偿;(iii)-测量本底;(b) 阿伦方差曲线:(i)-无补偿;(ii)-有补偿;(iii)-测量本底
Figure 6. Experimental results [50]. (a) Timing fluctuation curves: (i)-without compensation; (ii)-with compensation; (iii)-measurement floor; (b) Allan deviation curves: (i)-without compensation; (ii)-with compensation; (iii)-measurement floor
图 7 基于光学相位补偿技术的水下激光频率传递[51]。CW: 连续波;λ/2:半波片;PBS: 偏振分束器;λ/4:四分之一波片;PD:光电探测器;PI:比例-积分控制器;HM:半反射镜
Figure 7. Laser-based underwater frequency transfer based on optical phase compensation technique [51]. CW: continuous wave; λ/2: half-wave plate; PBS: polarization beam splitter; λ/4: quarter-wave plate; PD: photodetector; PI: proportion–integration controller; HM: half reflected mirror
图 8 实验结果[51]。(a) 定时抖动曲线:(i)-无补偿;(ii)-有补偿;(iii)-测量本底;(b) 阿伦方差曲线:(i)-无补偿;(ii)-有补偿;(iii)-测量本底
Figure 8. Experimental results [51]. (a) Timing fluctuation curves: (i)-without compensation; (ii)-with compensation; (iii)-measurement floor; (b) Allan deviation curves: (i)-without compensation; (ii)-with compensation; (iii)-measurement floor
图 9 基于终端相位补偿技术的水下多址激光频率传递[56]。TX: 发送端;RX: 接收端;VCO: 压控振荡器;λ/2:半波片;PBS: 偏振分束器;λ/4:四分之一波片;PD:光电探测器;PI:比例-积分控制器
Figure 9. Laser-based multiple-access underwater frequency transfer based on terminal phase compensation technique [56]. TX: transmitting site; RX: receiving site; VCO: voltage-controlled oscillator; M1: mirror 1; M2: mirror 2; Mn: mirror n; λ/2: half-wave plate; PBS: polarization beam splitter; λ/4: quarter-wave plate; PD: photodiode; PI: proportion–integration controller
图 10 实验结果[56]。(a) 定时抖动曲线:(i)-无补偿;(ii)-有补偿;(b) 阿伦方差曲线:(i)-自由运转的VCO B;(ii)-无补偿;(iii)-有补偿;(iv)-商用铯原子钟Microsemi-5071A
Figure 10. Experimental results [56]. (a) Timing fluctuation curves: (i)-without compensation; (ii)-with compensation; (b) Allan deviation curves: (i)-free running VCO B; (ii)-without compensation; (iii)-with compensation; (iv)-commercial Cs clock Microsemi-5071A
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