The ever-increasing demands in traffic fueled by bandwidth hungry applications are pushing data centers to their limits challenging the capacity and scalability of currently established transceiver and switching technologies in data center interconnection (DCI) networks. Coherent optics emerged as a promising solution for inter-DCIs offering unprecedented capacities closer to data centers and relaxing the power budget restrictions of the link. QAMeleon, an EU funded R and D project, is developing a new generation of faster and greener sliceable bandwidth-variable electro-optical transceivers and WSS switches able to handle up to 128 Gbaud optical signals carrying flexible M-QAM constellations and novel modulation techniques. A summary of the progress on the QAMeleon transponder and Reconfigurable Optical Add/Drop Multiplexer (ROADM) concepts is presented in this paper.
Worldwide, higher-order modulation formats are intensively investigated to further increase the spectral efficiency for
building the next generation of high-speed metro systems. IQ-modulators, coherent receivers and electronic equalizers
are hereby discussed as key devices. We report on system design issues as well as on HHI's latest achievements in
developing InP based high-speed modulators and coherent receiver frontends.
Recent development trends in InP-based optoelectronic devices are illustrated by means of selected examples. These include lasers for uncooled operation and direct modulation at 10 Gbit/s, complex-coupled lasers, which exhibit particularly low sensitivity to back reflections as well as monolithic mode-locked semiconductor lasers as ps-pulse sources for OTDM applications. Furthermore, a Mach-Zehnder interferometer modulator for high bit rate applications (40 Gbit/s and beyond) is described, and finally, photoreceivers and ultra high-speed waveguide-integrated photodiodes with > 100 GHz bandwidth are presented, which are key component for high bit rate systems, advanced modulation format transmission links, and for high speed measurement equipment as well.
In this contribution the material properties of polycrystalline (Cu,Ag)(In,Ga)(S,Se)2 thin films and their suitability for heterojunction solar cells are discussed. The copperchalcogenides play an important role in the formation of these films. However, a deteriorating impact of these secondary phases on the cell performance exists. Methods to overcome this dilemma are presented. The role of the morphology and of the chemistry of grain boundaries is illustrated in the CuGaSe2 and CuIn(S,Se)2 system. Important parameters for the design of a heterojunction solar cell are discussed. During the course of this work solar cells with efficiencies exceeding 14% could be obtained.