Near-IR and Mid-IR Wave Propagation through Patchy Fog

A Free-Space Optics (FSO) propagation experiment is running in Milan, Italy, since September 2022, in the framework of the Joint Lab between Huawei and Politecnico di Milano in collaboration with Consiglio Nazionale delle Ricerche (CNR). The set-up includes two co-located FSO links: a prototype Mid-IR link (10.6 µm) and a commercial Near-IR link (1.550 µm) over an 800-m path. Meteorological data are collected by two visibility sensors, two disdrometers, and a weather station. Data from a case study of moderate fog that occurred in winter 2022 highlights that the spatial distribution of fog is highly non-homogeneous along the path, hence, simple prediction models based on single-point measurements of the visibility may incur in large errors. Moreover, the comparison of path attenuation time series shows that the Mid-IR link performs better than Near-IR.