Frequency-domain equalization technology for a vortex optical multiplexing system

Orbital angular momentum multiplexing communication, as an emerging multiplexing technology, provides a new way to improve channel capacity and spectral efficiency. However, factors such as atmospheric turbulence can lead to signal fading and mode crosstalk, which, in turn, affects the system performance. In this paper, a dual-mode switching constant mode-least mean square (CMA-LMS) frequency-domain equalization scheme is applied to a four-channel orbital angular momentum multiplexed communication system with the aim of suppressing crosstalk in the system, and the performance of the algorithm is evaluated by means of the constellation diagrams, bit error rate, computational complexity, and convergence speed. The results show that the CMA-LMS frequency-domain equalization can effectively reduce the system bit error rate and suppress the system crosstalk. Compared with the time-domain CMA-LMS equalization algorithm, its computational complexity is significantly reduced, the convergence speed of the algorithm is faster, the bit error rate is reduced by 0.3 orders of magnitude, and the error vector magnitude value decreased by 3.6%.