Low linewidth lasers for enabling high capacity optical communication systems

Coherent communications have become a commercial reality with the deployment of 40 G and 100 G systems using Quadrature Phase Shift Keying (QPSK) in the core network. In the next evolution of these systems higher order modulation formats have the potential to significantly increase capacity while maintaining the baud rate at levels which allow the use of readily available lower cost electro-optics and electronics. Higher order modulation schemes have a lower tolerance to phase noise making low linewidth lasers a requirement. In this work we will present results from using different single mode and wavelength tuneable laser devices in optical coherent systems.