  Progress in optical wireless communication (OWC) has unleashed the potential
to transmit data in an ultra-fast manner without incurring large investments
and bulk infrastructure. OWC includes wireless data transmissions in three
optical sub-bands; ultraviolet, visible, and infrared. This paper discusses
installing infrared OWC, known as free space optics (FSO), systems on top of
installed radio frequency (RF) networks for outdoor applications to benefit
from the reliability of RF links and the unlicensed broad optical spectrum, and
the large data rates carried by laser beams propagating in free space. We
equally review commercially available solutions and the hardware requirements
for RF and FSO technology co-existence. The potential of hybrid RF/FSO for
space communication is further discussed. Finally, open problems and future
research directions are presented.
