The Internet today transmits hundreds of terabits per second, consumes 9% of all electricity worldwide and grows by 20-30% per year(1,2). To support capacity demand, massively parallel communication links are installed, not scaling favourably concerning energy consumption. A single frequency comb source may substitute many parallel lasers and improve system energy-efficiency(3,4). We present a frequency comb realized by a non-resonant aluminium-gallium-arsenide-oninsulator (AlGaAsOI) nanowaveguide with 66% pump-tocomb conversion efficiency, which is significantly higher than state-of-the-art resonant comb sources. This enables unprecedented high data-rate transmission for chip-based sources, demonstrated using a single-mode 30-core fibre. We show that our frequency comb can carry 661 Tbit s(-1) of data, equivalent to more than the total Internet traffic today. The comb is obtained by seeding the AlGaAsOI chip with 10-GHz picosecond pulses at a low pump power (85 mW), and this scheme is robust to temperature changes, is energy efficient and facilitates future integration with on-chip lasers or amplifiers(5,6).