Live Demonstration: Optical Communications using Solar Cells

This live demonstration showcases an optical communication system dubbed Optical Frequency Identification (OFID) that can be used to identify and track objects or animals as well as to sense environmental variables. The system consists of one or more optical tags and an optical reader. Each optical tag includes a GaAs solar cell, a low-power FPGA, an energy harvesting circuit and two sensors (light and temperature). GaAs solar cells are more efficient than their Si counterparts due to their direct bandgap electronic structure, which also makes them good emitters of infrared (IR) light when stimulated with light or with an electric current. This property, called luminescence, is exploited here to design electronic tags that use their on-board GaAs solar cells for three functions: 1) to transmit data (by modulating their IR luminescent emissions), 2) to harvest energy and 3) to receive information (by virtue of their photo-transduction property) [1] , [2] . The tags’ transmissions are received and decoded by the optical reader, which consists of a focusing lens, a photodiode, a trans-impedance amplifier followed by a gain stage and a digital decoder (implemented on an FPGA). Fig. 1 shows the live demonstration setup. It includes the optical tags, an optical reader, an oscilloscope to visualize received waveforms and a laptop to display received data packets.