Contents 1 Introduction
Further ongoing rapid growth of internet and multi-media data transfer worldwide requires economic and high capacity (≥ 1 Tb/s) optical transmission networks in future. For this purpose, different WDM technologies utilizing advanced, spectrally efficient modulation and detection formats are currently in the focus of network designers and system vendors (e.g., D(Q)PSK, PolMux DQPSK, multilevel x-QAM). The success of such transmission networks will strongly rely on the availability of compact, high performance, reliable, and low cost device modules as basic active or passive network building blocks (e.g. transmitters, receivers, routers). Low power consumption is another important issue which has to be considered as well. In order to meet predetermined system specifications and requirements, the use and combination of monolithic and hybrid integration technologies represent a promising approach for commercial component fabrication (“monolith-ic-on-hybrid” technique, [1]). Obviously, both have their own pros and cons because there is no single material system and technology available so far which meets all existing demands for practical device and network applications. But the “monolithic-on-hybrid” technique has the potential to benefit from the advantages of both approaches. However, these have been improved considerably in the last two years and moved already from research status towards commercial application.
