Quantum-Dot Semiconductor Optical Amplifiers for Energy-Efficient Optical Communication

Abstract

Quantum-dot (QD) based semiconductor optical amplifiers (SOAs) are key components for a large number of different applications in particular for all-optical communication networks. They are superior to classical semiconductor amplifiers in many important respects. Multi-wavelength amplification and signal processing at symbol rates larger than 40 GBd and operation in advanced modulation formats is needed in these networks. An introduction into the basics of QD SOAs as well as their key parameters is given at the beginning of this chapter. A novel concept for direct phase modulated signal generation is presented, unique for QD based SOAs. Error-free 25 GBd differential-phase shift keying (DPSK) signal is demonstrated, based there upon. The unique QD properties, i.e. decoupled gain dynamics of the various bound QD states, allows amplifying signals in dual-communication-band configuration both for small and large wavelength differences. Error-and distortion-free amplification of bidirectional 40 GBd on-off keying (OOK) signals, exhibiting a spectral separation of more than 91 nm is presented. Finally, all-optical wavelength conversion (AOWC) of phase-coded signals using four-wave mixing is shown. A guideline for the optimization of the conversion efficiency is given. Eventually error-free 40 GBd differential (quadrature) phase-shift keying (D(Q)PSK) AOWC is demonstrated.