VCSELs: prospects and challenges for optical interconnects

Ever increasing clock rates in computers, presently just passing 1 GHz, and ever growing traffic in the internet with data rates above 1 Terabit per second observed in single-fiber backbone strands indicate the stringent speed requirements imposed on current and future data distribution and data processing systems. It is generally agreed upon that such high data rates can be transmitted most favorably by using optical techniques. Moreover, vertical-cavity surface-emitting laser diodes (VCSELs) are considered almost ideal transmitters for short distance optical interconnects such as local area computer networks, rack-to-rack or board-to-board interconnects, or eventually maybe even inter-chip data links. Low cost mass fabrication with ready on-wafer testing are obvious advantages of VCSEL sources compared to conventional edge emitting laser diodes. It is the purpose of the present contribution to review VCSEL based optical interconnects and point out future demands