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

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
_b
(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
_b
compared to 2-CAP for the same bit error rate target. The R
_b
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
_b
). 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
_n
²
of 2.4 × 10
^-15
m
^-2/3
compared to a clear channel condition.