1.25Gbps optical links for mobile handsets

This paper presents a 1.25 Gbps optical links design for mobile handsets. The system consists of an optical connector and a SER/DES main chip. The former contains an 850 nm VCSEL (vertical cavity surface emission laser), a GaAs-PIN photodiode and a transimpedance amplifier (TIA). The later includes a serializer, a deserializer, a VCSEL driver, a limiting amplifier, a PLL and a CDR. The chip and TIA were fabricated in a 0.13 um CMOS process with MIM capacitors. A digital type CDR with fine timing controls allows sharing a VCO between transmitter and receiver, resulting in reduced both power consumption and silicon area. The system fully demonstrated a 1.25 Gbps data and video stream transmission, consuming 108.4 mW of power under 1.2 V/3.3 V supply voltages.