A Mode Coding System for Communication Based on Orbital Angular Momentum

This article describes an encoding method for the orbital angular momentum(OAM) mode used in communication. Based on the mutual orthogonal characteristics between different mode OAM beams and the principle of electric field superposition, the OAM beams of different modes are superimposed. The number of OAM modes corresponds to a binary sequence of the same length, and each mode represents a data bit, thereby achieving OAM mode encoding. This article designs an 8-element uniform circular array(UCA) that can generate -3 to +3 OAM modes, encoding a 6-bit binary sequence. The coaxial transmission of seven representative multimodal OAM beams is simulated using the parabolic equation(PE) method, and mode analysis is performed to verify the correctness of the scheme.Adding Gaussian white noise to the OAM beam can make the bit error rate(EBR) as low as 0 even when the signal-to-noise ratio(SNR) is -10dB and an appropriate decision threshold is adopted. It reflects the excellent anti-noise performance of the encoding system.