Elastic Optical Networks have been the most promising technology in the next generation of transport networks due to their flexibility of spectrum assignment. Routing and spectrum assignment is one of their key issues. Several routing and spectrum assignment algorithms have been introduced in recent years. In this research, we propose a novel spectrum assignment algorithm called constrained-lower-indexed-block policy. This policy is based on K shortest paths and has the capability to assign a lower indexed spectrum block on some a path to a connection request by the constraint that, length of the path should not increase too much. Simulation results show that the proposed policy can greatly reduce the blocking probability compared with two well-performed policies.

弹性光网络由于其频谱分配的灵活性，已成为下一代传输网络中最有前途的技术。路由和频谱分配是其关键问题之一。近年来已经引入了几种路由和频谱分配算法。在这项研究中，我们提出了一种新的频谱分配算法，称为约束低索引块策略。该策略基于K条最短路径，并具有以下能力：在路径长度不应增加太多的约束下，在某个路径上为连接请求分配索引较低的频谱块。仿真结果表明，与两种性能良好的策略相比，该策略可以大大降低阻塞概率。