In this work, an overview of requirements for compact optical modules and devices is presented, focusing on optical laser sources. Regarding coherent applications, the laser must have narrow linewidth, while, at the same time, be compact and present low power consumption, targeting C-form factor pluggable (CFP) modules. Latest results obtained by our group on laser development are presented, showing that the External-Cavity Laser (ECL) can fulfill the requirements for this application.