Elastic optical interface with variable baudrate: Architecture and proof-of-concept

Varying the symbol rate is an alternative or complementary approach to varying the modulation format or the channel spacing to turn optical networks into elastic networks. We propose to allocate just-enough bandwidth for each optical connection by adjusting the symbol rate such that the penalty originating from long cascades of optical filters is contained. This helps reduce overprovisioning for lightpaths where full capacity is not needed, by (i) eliminating unnecessary regenerators and (ii) reducing the power consumption of terminals, when the clock rate of electronics is reduced along with the baudrate. We propose a novel architecture for an elastic optical interface by combining a variable bitrate transceiver, paired with an elastic aggregation stage, with software-defined control. We then report a real-time field-programmable-gate-array-based prototype that delivers flexible transport frames to be sent with a polarization-division multiplexed quadrature phase-shift keying modulation format. We interconnect this prototype with a commercial optical transport network switch and a centralized controller. We demonstrate fast and hitless reconfiguration of the interface and measure the reconfiguration time of hardware logic (<450 μs), as well as end-to-end control and the data plane (<0.9 s).