Feedback-resistant p-type doped InAs/InP quantum-dash distributed feedback lasers for isolator-free 10 Gb/s transmission at 1.55 μm

Abstract

The tolerance to external optical feedback of p-type doped InAs/InP quantum-dash-based distributed feedback (DFB) lasers is investigated for different values of the Bragg-grating coupling coefficient. We show that p-doping of the active layer not only enhances the differential gain but also results in small values of the linewidth enhancement factor, both parameters contributing to an increased tolerance to external optical feedback. A −18 dB onset of coherence collapse is reported for antireflection-coated devices, demonstrating the compatibility of quantum-dash-based DFB lasers with isolator-free operation.