Tip/tilt aberration compensation based on a pre-correction model for free space optical communication

Free space optical communication (FSOC) is a promising technology for 6G wireless networks with the advantages of high bandwidth and low cost. However, atmospheric turbulence severely degrades receiver coupling efficiency, especially in small-aperture MIMO systems. These systems simplify the correction of high-order atmospheric aberrations by decomposing them into low-order tip/tilt aberration using concatenated small-aperture receivers. However, current correction strategies without any consideration for device delays and the random, time-varying nature of turbulence limit their effectiveness. In this paper, we propose a neural network-based pre-correction model that utilizes LSTM to anticipate the evolving characteristics of tip/tilt aberration induced by atmospheric turbulence, thereby allowing valuable response time for the correction device to execute precise adjustments. Testing under five turbulence conditions demonstrated an average improvement of 4.54 dB in coupling power (CP), with bit error rates reduced from 0.068 to near zero, achieving telecom-grade performance. This work offers a cost-effective solution for enhancing FSOC systems and provides insights for aberration correction in dynamic environments.