Impact of optical flexibility and sub-band switching on multi-layer transport network architectures

In this paper, we present how it is possible to still increase the global capacity of the currently deployed 100 Gbps based multi-layer transport networks thanks to the introduction of the sub-wavelength switching concept on future flexible optical add-drop multiplexers (FOADM). Such concept relies on the capabilities of the flexible node to adjust the optical channel characteristics to the service demand requirements. The technical solution uses coherent orthogonal frequency-division multiplexing as modulation to manage, with a very fine granularity, sub-wavelength optical switching. Multi-band techniques create super-channel to gather sub-wavelength together in order to increase the optical channel transmission capacity up to ultra-high data rate such as 1 Tbps. After having demonstrated performances of the solution, we evaluate, through typical use cases, the opportunity to introduce such flexible networking concept in future multi-layer transport networks and detail its advantages in terms of aggregation. Beyond techno-economic comparisons, the study integrates operational constraints and outlines the basis of future optical network planning.