ROADM express layer design strategies for scalable and cost-effective multi-fibre DWDM networks

The usual strategy of augmenting capacity between consecutive generations of DWDM networks by increasing the bit rate per channel is starting to be challenged as theoretical capacity limits are approached. Hence, capacity augmentation alternatives such as using more wavelength bands, exploiting multi-mode fibre transmission and deploying additional fibre pairs or multi-core fibres are being investigated. The adoption of one or more of these alternatives will impact the architecture of ROADM nodes. Particularly, a significant increase in the number of fibre pairs incoming/outgoing from a node can be expected when using multi-fibre links, demanding more complex and expensive switching devices and/or configurations. This work addresses the described forward-looking scenario, proposing and evaluating novel design strategies for the express layer of ROADM nodes such that scalability and cost-effectiveness are preserved while mitigating the potential increase of traffic blocking.