CMOS optical interface for high speed serial link : design and implementation

Abstract

The need for high-bandwidth and low cross talk data transfer in short distance as well as long distance applications such as DVI, Infiniband, Fiber Channel, Gigabit Ethernet and etc has forced to replace the conventional electrical link with a novel optical link. Furthermore, the demand for high integration optical interface circuits with existing digital blocks and for low cost fabrication has brought CMOS technology the primary process to satisfy the requirements. This research aims at providing a prototype consisting of commonly required blocks such as 8b/10b encoding, 10b/8b decoding, 10-to-1 serializer, 1-to-10 deserializer, phase-locked-loop, timing recovery, laser diode driver and front-end analog amplifier. A transmitter and receiver test chips, fabricated in a 0.25um CMOS process, have three pair of 8bit parallel data lines associated with electrical interface and three pair of stream data line associated with optical interface. The optical links are designed to operate up to 2.5Gbps/pin at 2.5V power supply. At the aimed data rate of 2.5Gbps, the operation is verified by measuring eye diagram of the transmitter. For the receiver, up to 1.25Gpbs the operation was confirmed by measuring the regenerated data channel output with the recovered clock.