A buried heterostructure based on Fe-doped InP semi-insulating layers is optimised for both high output power and large modulation bandwidth operations up to 70degreesC in a 10 Gbit/s directly modulated 1.3 mum lnGaAsP/InP distributed feedback laser. The slope efficiency of 0.19 W/A and -3 dB bandwidth of 10 GHz at 1.5 times threshold cur-rent is demonstrated experimentally.