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 (<italic>m</italic>-CAP) modulation scheme for a range of FSO/VLC link lengths and <italic>m</italic>-CAP parameters (i.e., the roll-off factor of the filters and a number of subcarriers) in terms of the data rate <inline-formula><tex-math notation="LaTeX">$R_b$</tex-math></inline-formula> (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 <inline-formula><tex-math notation="LaTeX">$R_b$</tex-math></inline-formula> compared to 2-CAP for the same bit error rate target. The <inline-formula><tex-math notation="LaTeX">$R_b$</tex-math></inline-formula> 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., <inline-formula><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>39% degradation in <inline-formula><tex-math notation="LaTeX">$R_b$</tex-math></inline-formula>). 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 <inline-formula><tex-math notation="LaTeX">$R_b$</tex-math></inline-formula> is decreased by 30% for the refractive index structure parameter <inline-formula><tex-math notation="LaTeX">$C_n^2$</tex-math></inline-formula> of 2.4 <inline-formula><tex-math notation="LaTeX">$\times\; 10^{-15}$</tex-math></inline-formula> m<inline-formula><tex-math notation="LaTeX">$^{-2/3}$</tex-math></inline-formula> compared to a clear channel condition.