Abstract: The transport network which is the base of service to the end user always demands higher and higher quality levels in terms of: reliability, manageability, scalability and upgradeability. Therefore, fiber-optic transmission systems based on SDH for a long period occupied a prominent place in the transport networks of virtually all telecom operators. However, the advent and widespread of recent telecommunication and network services pose new demands and opportunities. New broad band services require revision of the capacity of existing transport networks operators. The focus in this study is in the telecommunications transport network SDH technology using wavelength division multiplexing to increase the network capacity. The goal is also to enable complex topologies with the objective of improving the efficiency of the network and expanding its functionality. The approach is based on the effective implementation of WDM, analysis redundancy schemes and on redundant P-cycles. Operators are faced with the need to support multiple generations of technology and communication. This is necessary to ensure the transmission of 2G and 3G voice traffics and provide intensive data for new applications and Internet access with the required quality of service.