Bidirectional Gigabits Per Second Spatial Diversity Link Using POF for Passive Optical Front-Ends

This paper presents a novel concept for spatial diversity using plastic optical fibre (POF)-based luminaire transmission for in-home networks. We show the feasibility of an optical transmission system using POFs, acting as optical front-haul, for realizing a high capacity wireless bidirectional link aided by a spatial diversity scheme allowing user mobility around the access points. The light coming out of the 1 mm core diameter step-index POF is highly divergent and, therefore, for each POF-end an optical lens is placed to adjust the size of wireless cells, in order to allow user's mobility or to adjust the number of users served by the access points. Thus, the access points are completely passive, hence no electrical powering is needed, resulting in low maintenance. In addition, active components such as light sources and detectors can be located remotely from the access points and they are connected to each other by POFs. Futhermore, we performed optical wireless experiments with an eye-safe visible light laser and therefore our wireless link is limited to 1.2 m and 45 cm diameter of coverage areas. We obtained multi-Gbps for downlink and uplink and compared the link performance using discrete multitone, pulse amplitude modulation, and Nyquist sub-carrier modulation.