A compact (13.38.05.6 mm) 40 Gbit/s 1.55-µm electroabsorption (EA) modulator monolithically integrated distributed feedback (DFB) laser diode (EML) [1] module integrated with a driver IC has been developed. Its compactness was realized by employing a broadband feed-through and a bias tee which were accurately designed by 3-dimensional (3D) electromagnetic simulation. It was confirmed that the simulation results of the frequency response and the actual measurement results are corresponding well. Clear eye opening of the 40 Gbit/s optical output waveform of the fabricated EML module was observed. Degradation was not observed even when the 40 Gbit/s electrical signal was launched into the module via the flexible printed circuit (FPC).