LAUSR

The importance of the effects of weather on the transmission of high frequency signals has been recognized for some time [1]. As carrier frequencies increase from RF to millimeterwave to terahertz, the impact of adverse weather conditions on wireless data links is expected to become substantially more pronounced. At lower frequencies, these effects are typically dominated by attenuation due to molecular absorption [2]. However, at higher frequencies, as the wavelength approaches the size of dust, rain, or snow particles, the effects of Mie scattering are expected to become more significant, representing an important contribution to link budget calculations. Yet, few experimental studies have been reported in the terahertz range, particularly for the case of outdoor tests in adverse weather conditions which may pose a threat to sensitive measurement equipment. Ma and Federici have described controlled weather chamber measurements for modulated data links for a few simulated situations such as rain, fog, dust, and turbulence [3–7], but snow conditions are difficult to simulate indoors. Jeon and Grischkowsky reported a broadband characterization of long-range (~ 180 m) outdoor transmission, comparing clear weather results to recordings in rain and snow [8]. These data indicated a relatively small change in the received power, a somewhat surprising result for a situation where the scattering particles (individual snowflakes) are comparable in size to the wavelength of the radiation. Here, we report the first characterization of a terahertz data link outdoors during a snow fall. On 13 March 2018, a significant snow storm was forecast for New England [9]. Anticipating this event, we assembled an 11-m outdoor line-of-sight data link, using the same equipment described in ref. [10]. The transmitter was placed under an overhanging roof, such that the first 3 m of the beam path was protected from the falling snow. For the remaining 8 m, the beam propagated through the snowfall to the receiver (see Fig. 1a). The carrier wave at 200 GHz was modulated using amplitude shift keying (ASK), with a data J Infrared Milli Terahz Waves (2018) 39:505–508 https://doi.org/10.1007/s10762-018-0486-2