Demonstration of a Hybrid FSO/VLC Link for the Last Mile and Last Meter Networks

Abstract

In this paper, a hybrid free-space optical and visible light communication (FSO/VLC) system was experimentally demonstrated as a solution to overcome the last mile and last meter access networks bandwidth bottleneck. We evaluate the system performance of a multiband carrier-less amplitude and phase (m-CAP) modulation scheme for a range of FSO/VLC link lengths and m-CAP parameters (i.e., the roll-off factor of the filters and a number of subcarriers) in terms of the data rate R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> (i.e., spectral efficiency). We show that for the configuration with a 1-m VLC link the 10-CAP offers more than a 40% improvement in the measured R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> compared to 2-CAP for the same bit error rate target. The R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> penalty due to the extension of a VLC-link span from 1 to 3 m reaches to 12.6 Mb/s for the 10-CAP scheme (i.e., ~39% degradation in R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> ). To fully cover all aspects of the hybrid FSO/VLC system, we also investigate the atmospheric turbulence effect on the 500-m FSO link where Rb is decreased by 30% for the refractive index structure parameter C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 2.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-15</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2/3</sup> compared to a clear channel condition.