Free space optical (FSO) communication is increasingly recognized as a critical component of future Information and Communication Technology(ICT) infrastructure, especially in non-terrestrial networks. This thesis explores the application of mid-infrared (MIR) wavelengths—specifically within themed-wave IR (MWIR, 3-5 μm) and long-wave IR (LWIR, 8-14 μm) atmospheric transmission windows—to enhance FSO system performance. Thesewavelengths are pivotal for achieving fast, reliable data transmission overlong atmospheric distances due to their reduced atmospheric absorption andscattering.Advancements in semiconductor sources and detectors that enable high speed and efficient signal transmission are essential for realizing the potential of mid-IR FSO. Unipolar quantum optoelectronics, including components such as quantum cascade lasers (QCLs), Stark modulators, quantum cascade detectors (QCDs), and quantum-well IR photodetectors (QWIPs), offer significant promise for developing advanced FSO systems. Additionally, the use of advanced modulation formats, such as pulse amplitude modulation (PAM)and discrete multi-tone (DMT), combined with intensity modulation direct detection (IM/DD) techniques, further enhances system performance. The integration of digital signal processing (DSP) is also explored to mitigate channel impairments and optimize the overall transmission quality. This work provides a comprehensive analysis of these technologies through subsystem and system-level experiments, demonstrating the feasibility of such optoelectronic components in achieving robust transmitter and receiver performance under controlled laboratory conditions. It addresses the major challenges and considerations necessary for transitioning these technologies from theoretical and experimental stages to practical deployment. In conclusion, this thesis not only enhances the understanding of MIRIM/DD techniques in FSO but also sets the stage for future research that could pave the way for widespread adoption of mid-infrared FSO technologies in and real-world applications, aiming at a transformative impact on global communications infrastructures.