CMOS integrated high speed light sensors for optical wireless communication applications

This work presents a single link CMOS high data rate receiver to be integrated in imaging diversity sensor arrays for optical wireless communication targeting indoor scenarios. To compete with existing radio frequency links, sensing and transmitting data in the hundreds of Mbits per second and above, the proposed data/light sensor is optimized at both the photodetector and circuit levels to provide 5Gps data rate from a single optical link using low cost, high yield standard CMOS technology. A novel photo-detector structure, Triple Well Interrupted N-finger photodiode, is proposed that can achieve a bandwidth up to 10 GHz at 1.2V reverse bias. To compensate for the decreased responsivity of the photodiode, a wideband, high gain and low noise transimpedance amplifier compatible with the speed-enhanced CMOS photodiode is implemented in 0.13μm CMOS technology. The amplifier chain achieves a measured bit error rate (BER) of 10^-12 at 5 Gbps corresponding to 2.8μA input current in presence of 1pF input capacitance representing the photodiode. The die area is 1106μm×895μm including a transimpedance amplifier (TIA), limiter and buffer and the power dissipation is 68mW from a 1.5V DC supply.