February 17, 2017

Elastic Optical Interface with Variable Baud-Rate: Architecture and Proof-of-Concept

  • Belotti S.
  • Bigo S.
  • Dupas A.
  • Dutisseuil E.
  • Layec P.

Varying the symbol rate is an alternative or complementary approach to varying the modulation format or the channel spacing, in order 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 penalty originating from long cascades of optical filters is contained. This helps reducing over-provisioning 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 Baud rate. We propose a novel architecture for an elastic optical interface combining a variable bitrate transceiver, paired with an elastic aggregation stage, with software-defined control. We then report a real-time FPGA-based prototype, delivering flexible transport frames to be sent with a PDM-QPSK modulation format. We interconnect this prototype with a commercial OTN switch and a centralized controller. We demonstrate fast and hitless reconfiguration of the interface and measure the reconfiguration time of hardware logic (<450µs) as well as end-to-end control and data plane (<0.9s).

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