An Optical Transceiver Powered by On-Chip Solar Cells for IoT Smart Dusts With Optical Wireless Communications

Abstract

Using optical communications for smart dust applications enables small size of transceivers and offers a potentially large power advantage over RF. This paper presents an optically powered transceiver, which consists of on-chip solar cells, an optical receiver, a storage capacitor, and a passive transmitter formed by a liquid crystal ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> ) modulator and a modulated retro-reflector (MRR). The transceiver circuit system has been fabricated using a standard 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {\mu }\text{m}$ </tex-math></inline-formula> CMOS process and the circuit area is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 {\times }1.7$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> excluding the MRR. Measurement results show that the complete transceiver can successfully work for 1-kb/s downlink and 10-b/s uplink under 0.5-V voltage supply and consume 53 nA totally. This indicates the transceiver can work at least in a 10-m range. It is successfully demonstrated that the transceiver scavenged the power from a 670-nm modulated laser beam sent by a base station (BS), extracted clock signal and the encoded data from the beam, decoded two designed instructions, switched the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> in the MRR and sent responses back to the BS. To the author’s best knowledge, this is the first time to present that an on-chip solar-cell powered transceiver realizes the two-way optical wireless communications for Internet of Things applications.