Few-Mode Fiber-Coupled Indoor Optical Wireless Communication in the Presence of Misalignment

Laser-based optical wireless communication (OWC) is a key enabler for achieving terabit aggregate throughput for future indoor wireless networks. Fiber-coupled optical transceivers are the most mature technology to realize ultra-high-speed transmission links. However, fiber-coupled OWC links are vulnerable to misalignment issues due to device vibrations. To alleviate the impact of misalignment, the single-mode fiber can be replaced by the few-mode fiber (FMF). This paper presents a refined model to assess the impact of FMF coupling on indoor OWC channels in the presence of misalignment. Moving beyond the traditional use of Gaussian beams, our approach encompasses a broader range of spatial beams, offering a more realistic perspective on fiber coupling losses. We diverge from the conventional far-field assumptions and idealized channel conditions, instead offering detailed theoretical insights into the effects of both pointing errors and angle of arrival (AOA) fluctuations caused by random device vibrations. Our simulations reveal varied coupling efficiencies for different incident modes across FMF modes when misalignments occur. Furthermore, we provide insights into the achievable data rates of indoor fiber-coupled OWC systems, showing the variation of the throughput with different transmitted mode orders.