The paper presents a comprehensive look at the perspectives on the use of THz in digital communication systems. The publication aims to focus on arguments that justify a significant increase in the frequency of radio links and their integration with fibre-based networks. Comparison of THz links with their microwave and optical counterparts is discussed from basic physical limitations to technological constraints. Main attention is paid to the available channel capacity resulting from its bandwidth and signal-to-noise ratio. The short final discussion is about technology platforms that seem to be crucial to the availability of suitable THz sources. According to the author, the biggest advantage of using bands in the range of several hundred GHz for a digital data transmission is their use for mobile communication over short distances, as well as for broadband indoor links. However, these applications require a development of compact electronic THz sources with low noise and power reaching single watts. This is beyond the range of the most popular silicon-based technology platform, although a significant progress can be expected with the development of technologies based on wide bandgap semiconductors. Fibre optic connections remain the unquestioned leader in communication over long distances and permanent links.

Cellular mobile communication networks are experiencing an important evolution with the emerging deployment of 5G networks and the successive decline in the use of previous generations in the years to come. In parallel, policies promoting ecological transition are gaining social impact and economic interest and this seems to be the trend in the near future. In the telecommunications market, the shift between two dominant generations could be an important opportunity to introduce renewable energy sources to green the sector, reducing the carbon footprint of the world-wide extended activity. This work analyses the current situation and provides an insight into the possibilities to incorporate renewable energy supplies, specifically photovoltaics (as it seems to be the most promising among clean electric sources), perhaps combined with small wind turbines in off-grid systems. Paper also compares the characteristics of standard facilities in Spain and Poland, two different European countries in terms of weather and insolation hours.