Abstract
This article demonstrates a fiber-based power-by-light system that is capable of delivering up to 6.2 W of continuous electrical power at common voltages of 3.3 and 5 V. This optical link includes bidirectional optical communication, for which the data stream from the base to the remote unit is realized by amplitude modulation of the laser beam over the same fiber. At the remote unit, a gallium arsenide-based photovoltaic (PV) laser power converter receives and converts the light. The data are demodulated with a dedicated electric circuit, while the power is forwarded to a dc-dc boost converter. The optical data uplink is realized over a separate optical fiber. In operation, a PV conversion efficiency of above 50% has been measured. For downlink data rates up to 115.2 kb/s, unperturbed signal integrities are demonstrated, at higher data rates, the signal integrity deteriorates. An assessment of power budget and power losses in the overall system is presented. Finally, a smart power management concept is introduced, which controls the laser output power with respect to changing electrical load, optimizes the operating point of the PV cell, and, thus, increases system efficiency for varying load operation. Thereby, it also minimizes laser and PV cell operating temperatures, and eventually prolongs the lifetime of the system.
Highlights
O PTICAL power transmission is an elegant way to supply power to sensors, actuators, and other electrical consumers with high isolation demands
To increase the average output power, the IrDA signal is modified for the amplitude modulation as follows [see Fig. 3(b)]: 1) the signal is flipped, 2) the pulsewidth Tpulse is shortened from 3/16 of the bit length Tbit to 100 ns, and 3) the modulation depth is reduced from 1 to 2/3, i.e., the laser does not shut off completely with “0” bit, but instead only drops to one-third of the power
The PV cell’s current- and powervoltage characteristics, as plotted in Fig. 5, have been measured separately at different optical input power under illumination with the 809 nm laser light coupled from the fiber to the PV cell
Summary
O PTICAL power transmission is an elegant way to supply power to sensors, actuators, and other electrical consumers with high isolation demands. Compared with conventional copper wiring, this technology provides unique benefits, such as galvanic isolation, avoidance of electromagnetic interference, replacement of copper cables with low-weight fiber, avoidance of electric sparks while ensuring highest reliability and the possibility for wireless power transmission through free space. Thereby, it enables new applications in various domains
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