Optical Grooming Capable Wavelength Division Multiplexing node architecture for beyond 100 Gbps transport

Abstract

Mixed-line-rate wavelength division multiplexing (WDM) networks with discrete channel spacing generalize the fixed grid WDM networks and can support mixed-electronic-optical grooming efficiently. For optical transport networks with beyond 100 Gbps containers, optical layer grooming is needed to take full advantage of variable grid spacing, as well as to improve spectrum utilization. In this work, we propose two new node architectures, Optical Grooming Capable Optical Cross Connect (OGC-OXC) and Optical Grooming Capable Reconfigurable Optical Add/Drop Multiplexer (OGC-ROADM), which are capable of optical layer grooming for optical transport networks beyond 100 Gbps and will be generally called Optical Grooming Capable WDM (OGC-WDM) networks. For OGC-WDM, we investigate dimensioning of the number of fibres per link and add/drop degree per wavelength at each node and propose two new heuristic algorithms, First-Fit and Weighted-Fit. Also, we analyse the expected spectrum utilization for mixed-electronic-optical grooming in OGC-WDM, which can also reduce the required resources. Simulation studies show the following: For dimensioning of OGC-WDM, in comparison to the First-Fit, the Weighted-Fit heuristic requires 25% less number of fibres and 60% less add/drop degree. Also, if the size of topology is large and range of normalized distance of requests is large, Weighted-Fit requires smaller scale of add/drop components, and it has 50% more fibres to add/drop degree ratio, and 50% less number of fibres and add/drop degree product, the latter of which is crucial in scaling OGC-ROADM nodes. We also find that the execution speed of First-Fit is ten times faster than that of Weighted-Fit. In addition, the mixed-electronic-optical grooming can reduce required resources. With OGC-OXC node architecture, if no extra fibre is allowed, the overhead of grid allocation reaches 33%, and if one extra fibre is allowed, the overhead of grid allocation reaches 12.6%. However, if electronic grooming is allowed, the corresponding overhead of grid allocation reaches 18.75% and 7.49% respectively. To control the cost of OGC-ROADM, cyclic arrayed wave-guide grating and optical cross connect are used and if traffic load is light, the size of the two can be reduced by 50% with smaller cyclic arrayed wave-guide grating.