Wavelength design and optical axis correction for bidirectional underwater laser communication with ATP

This paper addresses the issues of wavelength selection and isolation for underwater full-duplex laser communication automatic tracking of beacon light signals. A method for four-wavelength reception and transmission isolation in the blue-green light band is proposed, which utilizes watt-level semiconductor lasers to achieve beacon light signals with orders of magnitude divergence angles, aiding in rapid acquisition and alignment. The underwater transmission distance of beacon light is close to that of signal light with small divergence angles. Additionally, the hemispherical dome used for waterproof sealing in the underwater laser communication ATP device has a significant impact on the alignment consistency of beacon light and signal light axes. This paper simulates the non-parallelism of underwater optical axes using ray tracing and corrects the non-parallelism of underwater optical axes by presetting a reverse bias angle, addressing the feasibility issue of independent beacon light application in underwater ATP devices and improving the performance of underwater laser communication.