A Passive Optical Transmitter Using LC Switches for IoT Smart Dusts

Abstract

Using optical wireless communications for sensors enables low power and small size of the nodes, such as smart dusts. This paper proposes a passive optical transmitter for smart dusts. Two liquid crystal (LC) modulator circuits have been designed for the switching the liquid crystal cells in the transmitter. The circuits are fabricated using a standard $0.18\mu \mathrm{m}$ CMOS process. Measurement results show that they can work under 0. 5V supply and successfully do the switching as designed. The transmission data rate can be 10bps, which is limited by the response speed of the LC cell.