In this paper, the packaging aspects of directly modulated laser (DML) modules are investigated using detailed electromagnetic (EM) simulations. The packaging influences of the laser module are specified in two parts as RF connector and optoelectronic subsystem. By carefully optimizing the package structure, the simulation results show that the insertion loss of the proposed module is less than 1 dB up to 40 GHz. Then, a DML module is packaged and measured based on the optimized package scheme. A resonance free bandwidth of approximately 20 GHz is obtained with a 3 dB bandwidth of about 15 GHz.