Optical wireless channels that use modulated retro-reflectors can provide low-data rate communications to self-powered
'smart-dust' motes. The retro-reflectors are illuminated using a base station that incorporates diffractive beamsteering to
direct radiation onto the motes, and these return the radiation to an imaging receiver within the base station. The motes
consist of a photodiode to provide power, a novel logarithmic receiver to receive data from the base station, and a
modulating retro-reflector to send information from the mote to the base station.
Several of the components elements of this system have been implemented and tested. In this paper we report a
logarithmic receiver that can be self powered by the source communicating with it, and a retro-reflecting LC modulator
component that operates at 30b/s when driven at 0.7V. In addition an overall system model, together with the challenges
for future work are presented.
A key challenge for wireless sensor networks is minimizing the energy required for network nodes to communicate with each other, and this becomes acute for self-powered devices such as 'smart dust'. Optical communications is a potentially attractive solution for such devices. The University of Oxford is currently involved in a project to build optical wireless links to smart dust. Retro-reflectors combined with liquid crystal modulators can be integrated with the micro-machine to create a low power transceiver. When illuminated from a base station a modulated beam is returned, transmitting data. Data from the base station can be transmitted using modulation of the illuminating beam and a receiver at the micro-machine. In this paper we outline the energy consumption and link budget considerations in the design of such micro-machines, and report preliminary experimental results.