Robust multifunctional single-tone training sequence for free-space optical communication in strong turbulence

Area of Science:

• Optical communication systems
• Signal processing for optical networks

Background:

• Turbulence in free-space optical (FSO) communication significantly reduces received power and complicates frequency offset estimation (FOE).
• Diversity reception enhances receiver sensitivity but requires phase correction between branches before signal combining.

Purpose of the Study:

• To develop a robust frequency offset estimation (FOE) method for FSO communication.
• To introduce a low-overhead training sequence for efficient phase correction in diversity reception.

Main Methods:

• A novel robust frequency offset estimation (FOE) algorithm was proposed.
• A single, low-overhead training sequence was designed for inter-branch phase correction.
• A 10-Gbaud dual-polarization quadrature amplitude modulation (QAM) transceiver system was implemented and tested in a simulated turbulent channel.

Main Results:

• The proposed FOE method demonstrated robustness in challenging turbulent conditions.
• The single training sequence effectively enabled phase correction for diversity branches.
• The implemented system successfully performed data reception, demodulation, and digital signal processing (DSP) under simulated turbulence.

Conclusions:

• The developed FOE method and phase correction technique significantly enhance signal quality in turbulent FSO communication.
• The proposed approach offers an effective solution for overcoming FSO communication challenges in adverse environments.