The purpose of Traffic Engineering is to facilitate efficient and consistent network performance with simultaneous focusing on optimizing network resource utilization and traffic performance. A network can be represented as a graph with nodes as vertices and links as edges. Spectral graph theory is a useful study on the relationship between graph properties and the spectrum of the adjacency matrix or Laplace matrix. In this paper, an important spectral graph parameter known as spectral radius is considered. This paper proposes an approach in which the links are identified based on their significance in terms of spectral radius and the capacity is assigned to the links accordingly. The performance of the proposed scheme is tested on backbone optical networks in terms of network congestion and resource requirements which are the main objectives of traffic engineering.