Performance Analysis of OAM-Based Advanced Symbol Modulation Schemes for OFDM Over FSO System

Abstract

Previous orthogonal frequency division multiplexing over free space optics (OFDM-FSO) systems relied on signal strength, wavelength, and polarisation to multiplex data streams in order to improve signal quality and feasible connection range. Alternatively, this work leverages on orbital angular momentum (OAM) mode division multiplexing with multiple OAM modes (OAM + 1, OAM +2, OAM +3, OAM +4) encountering different modal coupling effects under atmospheric turbulence. Advanced modulation and coding schemes (QPSK, 16QAM, and 64QAM) are deployed to improve the bit-error rate (BER), packet error rate (PER), and achieve a connection range of 1000 m in a free space optical link. OAM +1 was shown to achieve average BER and PER of 10 -3 at SNR equals to 22 dB and 30 dB respectively.