LDPC-coded orbital angular momentum (OAM) modulation for free-space optical communication

TLDR

The paper proposes an orbital angular momentum (OAM) based LDPC‑coded modulation scheme for free‑space optical communication. The scheme employs both binary and nonbinary LDPC coding on OAM modes to achieve high‑speed transmission. It delivers 100 Gb/s optical transmission under strong turbulence, a 9.3 dB coding gain at 10⁻⁸ BER, reduced decoder complexity, and outperforms equal‑gain combining by about 2.5 dB.

Abstract

An orbital angular momentum (OAM) based LDPC-coded modulation scheme suitable for use in FSO communication is proposed. We demonstrate that the proposed scheme can operate under strong atmospheric turbulence regime and enable 100 Gb/s optical transmission while employing 10 Gb/s components. Both binary and nonbinary LDPC-coded OAM modulations are studied. In addition to providing better BER performance, the nonbinary LDPC-coded modulation reduces overall decoder complexity and latency. The nonbinary LDPC-coded OAM modulation provides a net coding gain of 9.3 dB at the BER of 10(-8). The maximum-ratio combining scheme outperforms the corresponding equal-gain combining scheme by almost 2.5 dB.