Robust and cost-efficient FSO transmission using a multi-mode fiber-coupled receiver
Manuel M. Freitas, Marco A. Fernandes, Pedro A. Loureiro, Paulo P. Monteiro, Fernando P. Guiomar, Gil M. Fernandes
Abstract
In this work, we experimentally exploit the use of free-space optics (FSO) transmission with multi-mode fiber (MMF) coupling towards robust optical wireless communication system, with enhanced flexibility and misalignment tolerance. Such analysis is carried out considering a 2.5 GHz cost-effective fiber-coupled multi-mode receiver together with advanced modulation techniques, such as multi-carrier modulation, probabilistic constellation shaping and entropy loading, achieving an overall bit rate of >40 Gbps with 6.7 bit/s/Hz spectral efficiency. Results show that the exploited MMF-coupling enables a 2-fold bit rate increase over a standard single-mode fiber (SSMF) for a 0.25 mrad pointing error. Finally, the interplay between FSO pointing errors and inter-modal dispersion is experimentally assessed for MMF lengths up to 500 m. Our results demonstrate that MMF can effectively be exploited in a quasi-single-mode propagation regime provided that the air-to-fiber coupling is performed with sufficient beam alignment accuracy.