Experimental demonstration of flexible bandwidth networking with real-time impairment awareness

Abstract

We demonstrate a flexible-bandwidth network testbed with a real-time, adaptive control plane that adjusts modulation format and spectrum-positioning to maintain quality of service (QoS) and high spectral efficiency. Here, low-speed supervisory channels and field-programmable gate arrays (FPGAs) enabled real-time impairment detection of high-speed flexible bandwidth channels (flexpaths). Using premeasured correlation data between the supervisory channel quality of transmission (QoT) and flexpath QoT, the control plane adapted flexpath spectral efficiency and spectral location based on link quality. Experimental demonstrations show a back-to-back link with a 360-Gb/s flexpath in which the control plane adapts to varying link optical signal to noise ratio (OSNR) by adjusting the flexpath's spectral efficiency (i.e., changing the flexpath modulation format) between binary phase-shift keying (BPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK). This enables maintaining the data rate while using only the minimum necessary bandwidth and extending the OSNR range over which the bit error rate in the flexpath meets the quality of service (QoS) requirement (e.g. the forward error correction (FEC) limit). Further experimental demonstrations with two flexpaths show a control plane adapting to changes in OSNR on one link by changing the modulation format of the affected flexpath (220 Gb/s), and adjusting the spectral location of the other flexpath (120 Gb/s) to maintain a defragmented spectrum.

Software defined elastic optical networking in temporal, spectral, and spatial domains

“…Section 5 discusses some aspects of the SDN control plane design for the proposed 3D-EON. Section 6 discusses how the supervisory channel and performance monitoring technique demonstrated in [8] for a 2D EON scenario can be applied also in the new 3D elastic optical networking. Section 7 summarizes our 2D/3D-EON testbed.…”

“…The offered load is controlled by changing the average of the Poisson process in the range over [0. 8,10] Figure 11 compares the blocking probability of the different provisioning algorithms in the 14-node NSFNET and the 24-node USBN network. The results show that fragmentation-aware RSSMA algorithm for 3D EON can greatly reduce the blocking probability compared with our previously proposed 2D fragmentation-aware RSMA algorithm for traditional EON.…”

“…This will be a critically important functionality to realize impairment-aware networking [8,43]. The spread-spectrum optical supervisory channel [8] used for the EON to monitor the entire spectrum at all times can be also used in 3D EON by introducing it on each OAM states. At each monitoring point, it will be necessary to use an OAM DEMUX, as the one shown above, to separate the different OAM states so that each state can be monitored independently.…”

“…In fact, while different OAM states can be orthogonal in free space, there will be crosstalk once the signal will be launched and transmitted over multimode optical fibers, thus necessitating sophisticated MIMO DSP. As we demonstrated in [8], using a real-time performance monitoring method that spans a broad and elastic spectral width, the network can dynamically and adaptively adjust the modulation format to maximize spectral efficiency while maintaining the required quality of service (QoS) and bit error rate (BER) performance even for signals that experience time-varying physical layer impairments (QoS-aware and impairment-responsive networking). We can encode supervisory channel information at low speed (e.g., 1.25 Gb/s) modulation with low modulation index (e.g., ∼0.1) on top of the data spectrum.…”

Real-time power control for dynamic optical networks - Algorithms and experimentation

“…1) include various emerging dynamic optical devices which have the potential to address these challenges. Dynamic devices include, for example, Reconfigurable Add/Drop Multiplexers (ROADMs) that can transparently switch the transmissions from one lightpath to another [18], modulators that can adapt to the link state [10], and bandwidth variable transceivers that can modify band gaps between adjacent [2], whose topology is used in order to evaluate the proposed algorithms. The highlighted nodes are used as part of the topology simulated in Section VI.…”