Performance Comparison between Optical and Copper Interconnects

Abstract

Interconnect is basically used for data transmission inside an electronic device or system. Generally, it is used when the transmission distance is short. Device dimensions shrinks on chip, with future technology nodes. Some modifications are needed to be made in interconnect designing process based on the criteria of delay uncertainty, power consumption, bandwidth and noise. The conventional copper interconnects are not able to fulfil different design requirements. Copper based interconnects are facing many challenges. Because of dispersion, reflections and ringing, attenuation and its variation with frequency the high-speed signals are distorted. The performance of parallel links in conventional devices is also limited by the cross talk due to coupling from neighbouring signals. Copper interconnects have high power consumption, high latency, high cross talk and limited bandwidth. Interconnects are responsible for 70 to 80% of the signal delay in high-speed systems at deep submicron technology. Advancements must be done during design stage. Optical interconnects can be considered as a another alternative to meet these requirements. Optical interconnect due to its high bandwidth, low signal attenuation. Low signal delay, less power dissipation and cross talk, is an ideal candidate to tackle the challenges imposed by copper interconnects for on-chip applications at global interconnect level. Because modern ICs require high bandwidth, less delay and low power dissipation, a study of performance comparison between copper and optical interconnects is necessary. This comparison helps in setting clear goals on the requirements of optoelectronic devices to give high performance as compared to conventional electrical (copper) devices. For on-chip applications at global interconnect level, optical interconnects can reduce latency and provide high-bandwidth at relatively low power. Optical interconnects provide better results in terms of delay and power dissipation as compared to conventional copper interconnects at global interconnect level. In this thesis, delay and power dissipation results are simulated for optical and copper interconnects at various technology nodes. Simulation is done using SPICE simulation tool at global interconnect level. Optical interconnects give better delay performance as compared to conventional copper interconnects at each technology node. Power dissipation of optical and copper interconnects increases with future technology nodes because of higher clock frequency and leakage current, but optical interconnects dissipate less power as compared to copper interconnects. Therefore, optical interconnects give better performance in terms of delay and power dissipation than conventional copper interconnects at global interconnect level for on chip applications.