Atmospheric Turbulence-Immune Free Space Optical Communication System based on Discrete-Time Analog Transmission

TL;DR

This paper introduces a discrete-time analog transmission scheme for free-space optical communication that automatically adapts to atmospheric turbulence, improving image transmission quality and receiver sensitivity without complex modulation adjustments.

Contribution

The proposed DTAT-FSO scheme is a novel approach that directly maps source information to analog symbols, automatically adapting to channel variations and outperforming traditional digital schemes in turbulent conditions.

Findings

Improved receiver sensitivity by 2.5 dB in IM/DD systems

Enhanced image fidelity under same ROP conditions

Automatic adaptation to atmospheric turbulence

Abstract

To effectively mitigate the influence of atmospheric turbulence, a novel discrete-time analog transmission free-space optical (DTAT-FSO) communication scheme is proposed. It directly maps information sources to discrete-time analog symbols via joint source-channel coding and modulation. Differently from traditional digital free space optical (TD-FSO) schemes, the proposed DTAT-FSO approach can automatically adapt to the variation of the channel state, with no need to adjust the specific modulation and coding scheme. The performance of the DTAT-FSO system was evaluated in both intensity modulation/direct detection (IM/DD) and coherent FSO systems for high-resolution image transmission. The results show that the DTAT-FSO reliably transmits images at low received optical powers (ROPs) and automatically enhances quality at high ROPs, while the TD-FSO experiences cliff and leveling effects when the channel state varies. With respect to the TD-FSO scheme, the DTAT-FSO scheme improved receiver sensitivity by 2.5 dB in the IM/DD FSO system and 0.8 dB in the coherent FSO system, and it achieved superior image fidelity under the same ROP. The automatic adaptation feature and improved performance of the DTAT-FSO suggest its potential for terrestrial, airborne, and satellite optical networks, addressing challenges posed by atmospheric turbulence.