A 32 GHz microwave photonic pulse train is generated from a semiconductor fibre ring laser (SFRL) by injecting 1.6 GHz gain-switched Fabry-Perot laser diode (GS-FPLD) output. To achieve a stable modelocking of SFRL at 32 GHz by efficient cross-gain modulation of a semiconductor optical amplifier, individual lasing modes of the injecting 1.6 GHz GS-FPLD output are separated by 31.3 picoseconds by passing a dispersive fibre.