数据中心光互联通过IP网和光网络联合优化，实现了业务跨层疏导，但由于数据中心内部业务的突发性，突发业务被疏导到光网络，导致光网络业务的排队时延和建路时延增加，为此提出一种低时延路由频谱分配(RSA)算法。该算法将光纤中的频谱资源分为多个频谱层，在各频谱层并行建立光路，在频谱层中再用多个线程并行建路。各频谱层中当前建路时用的点和边组成了着色虚拟拓扑，将着色虚拟拓扑作为频谱层中资源使用的约束条件，并根据当前正在建路、未建路、新到达业务请求的变化在各频谱层重构着色和可用虚拟拓扑，来适应突发业务，快速疏导聚集在光网络中的业务请求。仿真结果表明，该算法减少了业务请求的光路平均建立时延，减小了光路建立时延方差和阻塞率，提高了频谱利用率，提升了用户体验质量(QoE)。

Requests grooming in multi-layer architecture are realized by the joint optimization of IP and optical networks in optical interconnection of data center. Due to the burstiness of requests in intra-data center, burst requests are groomed to optical network, which leads to the longer delay of queue and establishment of light paths of requests. In order to reduce the establishment delay of optical paths, we propose a routing and spectrum assignment (RSA) algorithm with low delay, which separates the spectrum resource of fibers into spectrum layers, and multi threads can set up optical paths in different spectrum layers in parallel. The algorithm sets up colored virtual topology with the points and edges of establishing optical paths in every spectrum layer, and the topology is used as constraints of resource utilization in current spectrum layer. The colored and usable virtual topologies in spectrum layers are reconfigured according to transformations of establishing, unestablished and new arrived requests, which can adapt bursts of requests and promptly groom the requests swarmed in optical network. The simulation results demonstrate that the proposed algorithm can efficiently reduce the average delay, delay variance of establishment of optical paths and blocking probability of requests, and improve the rate of spectrum utilization and quality of experience (QoE).