The authors have demonstrated singlemode fibre optic transmission using double fused laterally oxidised vertical cavity lasers (VCLs) operating at 1.55 mu m. Optimum performance was obtained with VCLs with an oxidised aperture of 6-7 mu m. These VCLs had a maximum sidemode suppression ratio of 47dB under pseudorandom modulation, a maximum bandwidth of 4.6GHz and a current modulation efficiency factor of 3.3GHz/root[mA]. A bit error rate <10(-9) was achieved for transmission over 200km at 622 Mbit/s.