© 2014 IEICE. A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. The effects of nonlinear distortions, due to a high launch power, on system performance are experimentally investigated. Single sideband (SSB) OFDM is employed to reduce the fibre nonlinearity effects.