The authors describe the generation of short (< 4 ps) optical pulses at a repetition rate of 40 GHz using an InP electro-absorption modulator. The technique of frequency resolved optical gating (FROG) is subsequently used to accurately characterize the generated pulses over a range of bias conditions and RF drive voltages. Our results show that the FROG technique will be vital for the optimization of RZ optical transmitters (in terms of pulse width, extinction ratio and frequency chirp) to be used in systems operating at 40 Gb/s and beyond, as standard measurement techniques will not suffice to optimize such high-speed hybrid WDM/OTDM or OTDM systems.