Free space optics (FSO) is a revolution in communication technology which uses light in free space for transmission. FSO systems are used for high data rate communication between two remote sites over distances up to several kilometers. It solves the problem between the client/user and ber-optic back-haul solving the last-mile problem. They are appealing for abroad application areas such as, ber back-up, local area network (LAN)-to- LAN connectivity, disaster recovery, backhaul for wireless cellular networks, high definition TV and wireless video surveillance/monitoring etc. The link reliability particularly in long range communication is limited mainly due to atmospheric turbulence-induced fading and sensitivity to weather conditions. The main consideration in the FSO design is the availability of link for different atmospheric conditions and providing a reliable quality of transmission (QoT) to the end user. An FSO network with distance based routing and wavelength assignment (RWA) technique does not provide any information about the current state of network, leading to a non-reliable communication. Based on the above the following analysis is been proposed: ●This work deals with the estimation of FSO link in different parts of India using Link Margin (LM). Here the meteorological data of various cities has been collected which evaluates the availability of the link for different attenuations in channel. ● FSO network with an adaptive routing and wavelength assignment (RWA) technique based on LM is proposed which selects the connection with higher availability rather than shortest distance. The overall network performance is being evaluated in terms of blocking probability (BP) based on network load and available link wavelengths. The estimated results can provide more knowledge about the reliability and deploy- ment of FSO network. In short, this thesis work estimates the Free space optics LM for Quality based network routing
