The need for high-speed and flexible data links is enhancing the popularity of mobile applications, and is a reason why wireless LAN and FSO are increasingly deployed to link sites that have line-of-sight. A free-space optical link is quick to establish and is not subject to licensing fees (unlike microwave radio). The speed required and distance to be bridged dictates the choice of technology, as does the funding available. When formulating the best approach for a secure and dependable link, we take into account the structural realities, climatic conditions, bandwidth required and distance to be bridged.