This volume is a monograph on parallel optical interconnects. It presents not only the state of-the-art in this domain but also the necessary physical and chemical background. It also provides a discussion of the potential for future devices. Both experts and newcomers to the area will appreciate the authors' proficiency in providing the complete picture of this rapidly growing field. Optical interconnects are already established in telecommunications and should eventually find their way being applied to chip and even gate level connections in integrated systems. The inspiring environment of the Basic Research Working Group on Optical Information Technology WOIT (3199), together with the excellent and complementary skills of its participants, make this contribution highly worthwhile. G. Metakides Table of contents 1 Perspectives for parallel optical interconnects: introduction . . . . . . . . . . . . . . . . . . . . . . . . . l Pierre Chavel and Philippe lAlanne 1. 1 Optical Interconnects and ESPRIT BRA WOIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 2 What are optical interconnects? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. 3 Optical interconnects: how ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. 3. 1 Passive devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. 3. 2 Active devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. 3. 3 Schemes for parallel optical interconnects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. 3. 4 Limits of optical interconnects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 4 Optical interconnects: why ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Acknowledgetnents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 First Section: Components Part 1. 1 Passive interconnect components 2 Free space interconnects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Philippe Lalanne and Pierre ChaveZ 2. 1 Introduction: 3D optical interconnects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2. 2 Optical free space channels and their implementations . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. 2. 1 Diffraction and degrees of freedom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. 2. 2 Two Qasic interconnect setups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .