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.