A Comparison of Silicon and Germanium Photovoltaic Power Conversion for Power-Over-Fibre
Saulius Juodkazis, Min Gu
Faculty of Computing, Health and Science
School of Engineering / Centre for Communications Engineering Research
In this study, we compare the practical implementation of both silicon and germanium Photovoltaic Power Converters (PPCs). Simulations have previously shown that silicon PPCs can produce up to 43% optical to electrical power conversion and germanium PPCs can produce conversion efficiencies as high as 22% when illuminated by 980nm light. Moreover, germanium can produce conversion efficiencies of up to 36% when illuminated by 1550nm light. Here, we compare these results to real power conversion efficiencies of off-the-shelf silicon and germanium photodiodes, producing 9.9% and 8.0% conversion efficiencies, respectively for 980nm. Furthermore, we show germanium produces conversion efficiencies up to 14.6% under illumination of 1550nm light. A discussion of the limitations is made. The results show there is a peak efficiency point corresponding to a specific input optical power. We also show that the power over fibre signal can be successfully combined with communications signals, using wavelength division multiplexing, and that the multiplexed signals can be separated without significant loss of signal, or power conversion efficiency. In addition, we investigate the affects of free space problems, such as divergence and misalignment, in both the lateral and longitudinal directions. As expected, optical alignment plays a significant role in producing maximum power conversion.