Rain Effects on FSO and mmWave Links: Preliminary Results from an Experimental Study

Optical and mmWave terrestrial links are somewhat considered complementary as they have a different sensitivity to fog and rain, i.e. the most frequent atmospheric impairments at mid-latitude. Hence, hybrid optical-mmWave systems that back-up each other according to weather conditions, have been proposed as they put together extremely large-bandwidth and high availability. However, in order to assess whether optical and mmWave systems can be considered complementary rather than competitors, the propagation effects should be quantified, possibly on a statistical basis. This paper presents preliminary results of the effects of rain on a commercial optical link at 1550 nm and a co-located dual-band mmWave link. It is shown that the degradation of the optical signal is not always well correlated with the microphysical properties of rain, Signal attenuation can be substantially underestimated if predicted by the electromagnetic theory, due to the concurrent action of other factors.