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.