Investigation on Orbital Angular Momentum Mode-Based Beam Shaping for Indoor Optical Wireless Communications

In this paper, we report a novel indoor optical wireless communications system employing orbital angular momentum (OAM) mode-based beam shaping. Different shapes of transmitted beams with various power distribution can be obtained by superposing different OAM modes incoherently with different power ratios. The bit-error-rate (BER) performance of the proposed system has been numerically and experimentally investigated. The results show that the effective coverage (BER<3.8 × 10⁻³) can be expanded significantly by employing OAM mode-based beam shaping scheme at certain power ratios between OAM₀ mode and higher-order OAM mode, compared to conventional OWC systems without OAM mode-based beam shaping scheme and the optimal performance for symbol rate of 10 Gbaud can be obtained when the power ratio of OAM₀/OAM₁ and OAM₀/OAM₂ is 0.3 and 0.33, respectively. Furthermore, the BER performance distribution in different directions within the optical cell has also been evaluated. It has been shown that less variation in the performance can be achieved in the system employing OAM₀ with OAM₂ based-beam shaping compared with that in the system employing OAM₀ with OAM₁ modes.