Real-Time Demonstration of Multi-Gigabit/s Free-Space Optical Communications Employing Femtosecond Laser Filaments in Complex Environment

Channel fading caused by environmental factors such as atmospheric turbulence, fog and clouds is one of the key issues that highly impedes the practical implementation and deployment of free-space optical (FSO) communications. To alleviate the channel fading and further improve the system performance, for the first time, we experimentally demonstrate a real-time multi-gigabit/s FSO communication system employing femtosecond laser filament, to the best of our knowledge, where the laser filament is used to generate a quasi-continuous air waveguide to guide the information-bearing light through atmospheric turbulence, fog and clouds. The bit-error-rate (BER) performance under different environmental conditions has been systematically investigated and analyzed. It is shown that with the help of the femtosecond laser filament, significant system performance improvement with BER below the 7% hard-decision forward error correction (HD-FEC) limit of 3.8×10 ^-3 can be obtained for most of the time regardless of the environmental conditions of atmospheric turbulence, fog and clouds. Our experimental results clearly present the feasibility and benefit of femtosecond laser filament for FSO communications in complex environment or for some emergency cases.