Today, most of the telecommunication networks apply fiber optics transmission carrying SDH (Synchronous Digital Hierarchy) or SONET (Synchronous Optical Network) signals. To overcome the problems arising due to increasing bandwidth demand, one solution is to install more fibers along a link. But will increase required equipment and therefore cost.Another very promising approach to increase link capacity is WDM. With WDM , multiple wavelength channels are carried over a single fiber without any interference.