Distributed MIMO Experiment Using LiFi Over Plastic Optical Fiber

This paper shows the feasibility of a networked LiFi system using a distributed multiple-input multiple-output (MIMO) link for optical wireless transmission and a plastic optical fiber (POF) link as a fixed front-haul between distributed optical front-ends, and a centralized signal processing unit. The concatenation of POF and optical wireless links yields an easyto-install all-optical LiFi system which is robust against both, blockage of individual light beams and electromagnetic interference. A significant cost-down appears by the use of colored LEDs to feed the POF link with multiple optical signals, and wavelength division demultiplexing filters. The spatial crosstalk in the wireless link and the spectral crosstalk over the POF link can be jointly compensated by the same end-to-end MIMO processing. A common signal model, which includes the combined effects of both links are provided to characterize the proposed all-optical LiFi system. We report the first experimental findings when using space-division multiplexing (SDM), i.e., multiple POFs, and wavelength-division multiplexing (WDM), i.e., multiple colors in the front-haul, indicating that the performance is mostly limited by the wireless link. Moreover, we show that the positions of mobile users in the wireless link, as well as gain variations and spectral crosstalk in the front-haul link, influence the singular values and the achievable data rates of the LiFi system.