DIQDOT

The DIQDOT project will develop novel GREEN optical sources for low cost, low consumption, athermal, access network infrastructure that will support a number of access network topologies. These high performance transmitters are based on a novel low dimensional material system consisting of quantum dashes (QD) grown on InP to reach the 1.55 µm fiber window. Besides high power and high bit rate (10 Gbit/s) operation, these transmitters will be capable of achieving transmission spans on standard fibre well beyond chromatic dispersion limits. More precisely we consider the disruptive integration of two innovative building blocks: • A directly modulated DFB laser (DML) with very low chirp based on the combination of high differential gain p-doped nanostructures, inducing low adiabatic chirp even at high current and high temperature, and an optimized laser technology leading to a very low transient chirp. (A further major asset of this QD-DML is its ability to operate isolator-free). • A monolithically integrated InP-based ring resonator allowing the efficient damping of “0 levels” for recovering an extinction ratio (ER) fully compatible with current access standards (ER>6dB). A hybrid solution based on commercial filters will be investigated in order to identify precisely the impact of filter shape on the 10Gb/s transmission properties, both in terms of performances and tolerances. The disruptive integration of both QD-DML and etalon filter on InP will open the way to a GREEN module for coarse wavelength division multiplexing. A phase shift section will ensure the right detuning between the DML wavelength and the etalon filter resonance and we would expect to maintain the optimized transmission performances in un-cooled operation. The compactness of this solution combined with the compliance with isolator free and un-cooled operation should lead to a very low-cost product compatible with existing packaging solutions such as a TO-can module. Such a development of a very simple, compact, isolator- and Peltier-free solution is fully in line with the GREEN TOUCH initiative dedicated to increasing ICT energy efficiency. Optimization of the low chirp source will rely on novel material growth approaches using vertically-stacked layers with a thin spacer together with p-type doping of the active layer. We in particular aim at a record modal gain of 60 cm-1, and linewidth enhancement factor alphaH29dB) over distances >60km, which is well beyond chromatic dispersion limits and state-of-the-art DML, will also be aimed at. Expected impact of the DIQDOT project encompasses both scientific and technical issues (by gaining further insight in strain-engineering of novel nanostructures and subsequent laser performance improvement and in the role of etalon filter to extend fiber spans for the long reach access networks), as well as NGPON standardization contribution by ORANGE through dissemination of our results.