Mode-locking of single-section Fabry-Pérot InAs/InP edge emitting quantum dash based lasers at 1.56 µm under continuous wave operation is studied by second-harmonic generation frequency resolved optical gating. Self-starting pulses of a width down to 374 fs can be observed after external chirp compensation using standard single-mode fiber (SMF-28). Pulse compression using different lengths of SMF-28 and pulse shape as well as phase dependence on bias conditions are investigated. Consistency with stepped-heterodyne technique for advanced pulse characterization is shown.