Elastic Optical Networks (EONs) allow the channel spacing and the spectral width of an optical signal to be dynamically adjusted and hence have become an important paradigm in managing the heterogeneous bandwidth demands of optical backbone networks. The entire available optical spectrum is divided into some spectrum slots which define the smallest granularity of bandwidth and optical signals with variable bandwidths can occupy different number of such slots. The constraints imposed by the physical layer of an EON require that the slots occupied by an optical signal from source to destination have to be consecutive and contiguous in terms of their relative position in the optical spectrum. Furthermore, the same spectrum slots need to be reserved throughout the entire optical signal's path from its source to destination. The above constraints make the routing and spectrum allocation (RSA) in EONs very challenging because unavailability of enough spectrum slots that together equals the spectral width of the optical signal associated with an end-to-end request, will result in blocking of the request. Recent developments in the physical layer technologies have made all-optical ‘slicing’ of a request possible and make the request to be ‘fit’ into multiple non-consecutive spectral slots in an EON. But these all-optical ‘slicers’ employ complex technologies and can be very costly to employ. In this paper, we propose a spectrum allocation scheme for an EON node architecture with these ‘slicers’ and we also formulate a modified RSA scheme for EONs employing slicers, both as a mixed-integer linear programming (MILP) model and a heuristic algorithm. Our main aim is to analyze the tradeoff between the number of slicers that can be used per node versus the spectrum utilization and bandwidth blocking rate. The numerical results show that the proposed scheme with slicers can significantly improve bandwidth blocking rate, compared to the conventional scheme without slicer.

弹性光网络（EON）允许动态调整光信号的信道间隔和频谱宽度，因此已成为管理光骨干网异构带宽需求的重要范例。整个可用光谱被分成一些频谱时隙，这些频谱时隙定义了最小的带宽粒度，带宽可变的光信号可以占用不同数量的此类时隙。EON的物理层施加的约束要求光信号从源到目的地所占据的时隙在其在光谱中的相对位置方面必须是连续且连续的。此外，在从信号源到目的地的整个光信号路径中，需要保留相同的频谱时隙。上述限制使EON中的路由和频谱分配（RSA）变得非常具有挑战性，因为无法提供足够的频谱时隙，这些频谱时隙一起等于与端到端请求关联的光信号的频谱宽度，将导致请求阻塞。物理层技术的最新发展使得对请求的全光“切片”成为可能，并使请求“适合” EON中的多个非连续频谱时隙。但是，这些全光“切片机”采用了复杂的技术，因此使用起来可能非常昂贵。在本文中，我们提出了使用这些“切片器”的EON节点体系结构的频谱分配方案，并且还针对采用切片器的EON制定了改进的RSA方案，既作为混合整数线性规划（MILP）模型，又作为启发式算法。我们的主要目的是分析每个节点可使用的限幅器数量与频谱利用率和带宽阻塞率之间的折衷。数值结果表明，与不带分片器的常规方案相比，带分片器的方案可以显着提高带宽阻塞率。