The authors present an expanded porous polytetrafluoroethylene terahertz fibre transmission link using resonant tunnelling diodes integrated with photonic-crystal waveguides as a transmitter and a receiver. The measured coupling efficiency between the terahertz fibre and the photonic-crystal waveguide integrated with a silicon tapered coupler is ∼30% with a 3 dB bandwidth of 50 GHz at the 0.3 THz band. Error-free 10 Gbit/s transmission and uncompressed 4 K high-definition video transmission have been successfully demonstrated using 1 m-long terahertz fibre.