Characterization and modeling of link loss for an outdoor free-space optics transmission system

In this paper we propose three low-complexity algorithms to estimate the time-varying loss of an outdoor 1550-nm free-space optics (FSO) link with 55-m transmission length. Longterm experimental measurements taken for different weather conditions demonstrate that the link loss can be predicted accurately while still using low-complexity algorithms

Adaptive probabilistic shaped modulation for high-capacity free-space optical links

Infrared free-space optics (FSO) provide an attractive solution for ultra-high-capacity wireless communications. However, the full potential of FSO is still being hindered by the apparent random fluctuations on the received optical power, which can be triggered by external factors such as atmospheric turbulence, weather instability, and pointing errors. Through the analysis of long-term experimental measurements, we identify the existence of significant time-domain memory in outdoor FSO links, which is found to be particularly strong under rainy weather conditions. Following this observation, we demonstrate that these memory effects can be effectively utilized to design accurate FSO channel estimation algorithms. Taking advantage of the arbitrary bit-rate granularity provided by probabilistic constellation shaping (PCS), and resorting to a simple moving average channel estimator, we demonstrate 400G+ transmission over a seamless fiber-FSO 55-m link with enhanced resilience towards adverse weather conditions. Comparing with unsupervised fixed modulation, we demonstrate a significant increase in average bit-rate (>35 Gbps) after continuous measurement over 3 hours, including raining periods

High-capacity and rain-resilient free-space optics link enabled by time-adaptive probabilstic shaping

Using time-adaptive probabilistic shaped 64QAM driven by a simple SNR prediction algorithm, we demonstrate >450 Gbps transmission over a 55-m free-space optics link with enhanced resilience towards rainy weather conditions. Through continuous measurement over 3-hours, we demonstrate 40 Gbps average bit-rate gain over unsupervised fixed modulation