Theoretical modeling and performance evaluation of the optical wedge pair for laser communication receiver

In free-space optical (FSO) communication systems, efficiently coupling incident light into single-mode fibers at the receiver is crucial for high-quality transmission. A receiver equipped with focusing capability not only enhances environmental adaptability but also reduces the tolerance requirements for optical fabrication and assembly. Thus, the study of adjustable focusing mechanisms for FSO receivers is of significant research interest and practical value. To address the stringent optical axis stability required for fiber coupling, this paper proposes a high-stability focusing mechanism based on an optical wedge pair structure. Geometric and physical optics models, coupled with an air gap compensation mechanism, are developed and validated through both simulation and experiment. The results demonstrate that the system achieves high-precision focusing, excellent optical axis robustness, and low sensitivity to actuator errors. Under conditions of identical actuator errors (10 µm straightness error and 150 µrad angular wobble), the maximum optical axis offset in the optical wedge pair system is only about 1/27 that of the conventional axial translation mechanism. This demonstrates a significant advantage in maintaining optical axis stability. The optical wedge pair approach effectively improves system adaptability, supporting the practical application of FSO communication systems.