WDM is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths of light to carry different signals. With this technique achievable bandwidth is about 320 G. Many bandwidth-intensive applications, such as video conferencing and video-on-demand services, require multicast services for efficiency purposes. WDM Optical networks are the best candidate for this type of applications. Avoiding O/E/O conversion to have all-optical network is one of the most important issues in this networks. In all-optical networks, each message is transmitted from the source to the destination by using a single wavelength. if there is no same wavelength in all of the links of the path, connection is blocked. To increase network performance, we can use wavelength converter in the switching nodes. If we use full wavelength converter, blocking probability is significantly decreased but, by introducing these O/E/O conversion-based wavelength converters into networks we loses the advantages of all-optical transmission and switching. Instead, we can use all-optical wavelength converter which is able to convert any given input wavelength to a limited number of output wavelengths. In this thesis, first we study previous works on multicasting in WDM optical networks and common routing algorithms. Then we add limited or all-optical wavelength converter to the switching nodes and according to simulation result, compare performanc