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Performance enhancement of free-space optical communications under atmospheric turbulence using modes diversity coherent receipt

Donghao Zheng, Yan Li, Honghang Zhou, Yiming Bian, Chen Yang, Wei Li, Jifang Qiu, Hongxiang Guo, Xiaobin Hong, Yong Zuo,

Optics Express · 2018 · 64 citations · 22 references

DOI Full text

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TL;DR

The larger the D/r0, the stronger the turbulence is, and vice versa. The study numerically and experimentally evaluates a free‑space optical receiver employing mode‑diversity coherent detection under moderate‑to‑strong turbulence. By utilizing a three‑mode photonic lantern with digital maximum‑ratio combining, a 40 Gbps QPSK signal is received, with turbulence quantified by the beam diameter to atmospheric coherence length ratio D/r0. Compared with conventional single‑mode fiber reception, the required transmitted power is reduced by 4.6 dB and 4 dB at 10 % interruption probability for D/r0 = 8 and 16, and by 4.2 dB and 5 dB at a BER of 2.2 × 10⁻² under the same turbulence strengths.

Abstract

This paper numerically and experimentally investigates the performance of free-space optical receiver using modes diversity coherent receipt under moderate-to-strong turbulence. By utilizing a three-mode photonic lantern with digital maximum ratio combining, a 40 Gbps QPSK optical signal is received. The turbulence strength is measured by the ratio of beam diameter to atmospheric coherence length, D/r0. The larger the D/r0, the stronger the turbulence is, and vice versa. Compared with conventional single mode fiber based receipt, the required transmitted power can reduce by 4.6 dB and 4 dB at 10% interruption probability under turbulence strength D/r0 = 8 and 16. The required transmitted power at bit error ratio of 2.2 × 10-2 can relax by 4.2 dB and 5 dB under turbulence strength D/r0 = 8 and 16.