Tbit/s line-rate satellite feeder links enabled by coherent modulation and full-adaptive optics

Area of Science:

• Optical Communications
• Satellite Technology
• Signal Processing

Background:

• Future satellite-ground networks require solutions to overcome radio frequency (RF) bottlenecks.
• Free-space optical (FSO) communication offers a path to Tbit/s data rates.
• Turbulence in the atmosphere significantly impacts FSO link performance.

Purpose of the Study:

• To demonstrate Tbit/s line-rate transmission over a 53.42 km FSO link mimicking a satellite-ground feeder link.
• To investigate the effectiveness of adaptive optics and advanced modulation formats in mitigating turbulence.
• To introduce and evaluate a novel four-dimensional BPSK (4D-BPSK) modulation for low signal-to-noise ratio (SNR) conditions.

Main Methods:

• Employed a full adaptive optics system to correct wavefront distortions.
• Utilized polarization-multiplexed high-order complex modulation formats.
• Introduced and tested constellation modulation (4D-BPSK) for high data rates at low SNR.

Main Results:

• Achieved net-rates up to 0.94 Tbit/s over 53.42 km under turbulent conditions.
• Demonstrated that adaptive optics does not degrade coherent modulation format reception.
• Showcased 13.3 Gbit/s and 210 Gbit/s FSO transmission at extremely low photon counts per bit (4.3 and 7.8, respectively) with a 10^-3 bit-error ratio.

Conclusions:

• Advanced coherent modulation coding combined with adaptive optical filtering are key to practical next-generation Tbit/s satellite communications.
• FSO communication is a viable technology for meeting future bandwidth demands in satellite networks.
• Adaptive optics and novel modulation schemes significantly enhance the robustness and performance of FSO links.