Software-defined defragmentation in space-division multiplexing with quasi-hitless fast core switching

Multicore fibres (MCF) offer the opportunity of both increasing communication capacity as well as offering enhanced flexibility in the network scenario. Software-defined networks (SDN) are capable of handling novel functionalities coming from physical layer with the aim of better exploit overall connectivity. In this paper, network defragmentation is considered combined with space-division multiplexing (SDM). In particular, SDN-driven effective defragmentation technique on a seven-core MCF is demonstrated. This paper includes a networking view about defragmentation principle exploiting SDN control plane. At the same time, an accurate model and numerical investigations reveal feasibility and system constraints. Push-pull operation for a coherent DQPSK transmission has been experimentally demonstrated together with full dynamic defragmentation. By using a highspeed- integrated dual-output intensity modulator switch for core adaptation in combination with hitless frequency shift, quasihitless SDN-driven reconfiguration performances are shown. Defragmentation for 40 Gb/s DQPSK and 80 Gb/s 16QAM signals is demonstrated. Switching from core 2 to core 1, 100-GHz frequency shift, and switching back to core 2 is obtained losing just 1800 and 2600 symbols, respectively.