Performance analysis of coherent optical communication based on hybrid algorithm

The performance of coherent free-space optical communication (FSOC) is often affected by atmospheric turbulence. Sensorless adaptive optics are widely used in coherent FSOC to mitigate the effect of atmospheric turbulence. However, the control algorithm for sensorless adaptive optics systems remains weak. To enhance the various performance indicators of coherent FSOC, we propose a hybrid algorithm to improve the coupling efficiency and mixing efficiency (ME) of the system while reducing the bit error rate (BER). This algorithm combines the fast convergence rate of the simulated annealing (SA) algorithm at the initial cooling stage and the beneficial convergence effect of the stochastic parallel gradient descent (SPGD) algorithm, avoiding the algorithm's need for more iterations and its tendency to enter local optimisation. The simulation results show that the performance of the proposed hybrid algorithm outperforms that of the traditional SPGD algorithm, regardless of the intensity of the atmospheric turbulence. The SA and hybrid algorithms display similar performances in strong atmospheric turbulence, while the hybrid algorithm shows better performance than that of the SA algorithm in weak atmospheric turbulence.