40 Gbit/s directly modulated lasers: Physics and application
Low cost and compact transmitters are key components for short reach and datacom applications in fiber communication systems. Bit rates of 40 Gbit/s are beyond the speed limitation of conventional directly modulated lasers. Lasers with an integrated electro-absorption modulator (EML) represent one possible solution. An attractive alternative are Passive Feedback Lasers (PFL). Here, the modulation bandwidth is significantly increased by an integrated feedback section. Underlying physics and functionality of the PFL are presented as well as the successful realization at wavelengths in the 1300 nm and 1550 nm regions. The performance of these PFLs is demonstrated in system experiments.