Patricia Layec

Next generation elastic optical networks: The vision of the European research project IDEALIST

In this work we detail the strategies adopted in the European research project IDEALIST to overcome the predicted data plane capacity crunch in optical networks. In order for core and metropolitan telecommunication systems to be able to catch up with Internet traffic, which keeps growing exponentially, we exploit the elastic optical networks paradigm for its astounding characteristics: flexible bandwidth allocation and reach tailoring through adaptive line rate, modulation formats, and spectral efficiency. We emphasize the novelties stemming from the flex-grid concept and report on the corresponding proposed target network scenarios. Fundamental building blocks, like the bandwidth-variable transponder and complementary node architectures ushering those systems, are detailed focusing on physical layer, monitoring aspects, and node architecture design.

Elastic optical networks: The global evolution to software configurable optical networks

Worldwide operator deployment of high-speed 100G coherent optical networks is currently underway. To ensure a competitive solution offering significant performance improvements to cope with the ever-increasing traffic demand, a novel network concept has been proposed for improved resource utilization based on “elasticity”; specifically, the ability to make a number of previously fixed transmission parameters tunable, for example optical data rate or channel spacing. The benefits are numerous, including increased network capacity, lower cost per bit, and improved energy efficiency and scalability. In this paper, we review the work carried out within the Cooperation for a Sustained European Leadership in Telecommunications (CELTIC) Elastic-Optical NETwork (EO-Net) project towards advancing the state of software-configurable optical networking. We identify the key building blocks for enabling elastic optical networks to provide desired performance improvements over static optical networks. We examine the design of elastic transponders capable of data rate adaptation, interfaces between client packet devices and transponders supporting flexible traffic aggregation, and associated algorithms for traffic grooming and routing. We also perform network cost/energy analyses. Finally, we review the experimental demonstration of such elastic functionalities.

Experimental Demonstration of Multivendor and Multidomain EON With Data and Control Interoperability Over a Pan-European Test Bed

The operation of multidomain and multivendor EONs can be achieved by interoperable sliceable bandwidth variable transponders (S-BVTs), a GMPLS/BGP-LS-based control plane, and a planning tool. The control plane is extended to include the control of S-BVTs and elastic cross connects, which combine a large port-count fiber-switch (optical backplane) and bandwidth-variable wavelength-selective switches, enabling the end-to-end provisioning and recovery of network services. A multipartner testbed is built to demonstrate and validate the proposed end-to-end architecture. Interoperability among S-BVTs is experimentally tested between different implementations. In this case, transponders are configured using the proposed control plane. The achieved performance with hard-decision and soft-decision FECs using only the information distributed by the control plane is measured against the performance of the single-vendor implementation, where proprietary information is used, demonstrating error-free transmission up to 300 km.

Real-time demonstration of software-defined Elastic interface for flexgrid networks

We demonstrate a real-time Elastic Interface for future flex-grid networks with a software-defined symbol rate transmission. Using PDM-QPSK modulation, live experiments show a line rate adaptation from 10.7 to 107Gbit/s with a sub-millisecond reconfiguration time.

Generalized Maximum Likelihood for Cross-Polarization Modulation Effects Compensation

We investigate the mitigation of nonlinearities with advanced digital signal processing focusing in particular on cross-polarization effects. Based on a relaxation of an analytical model derived for cross-polarization effects, this paper proposes a novel compensation method called generalized maximum likelihood. It performs a joint blind channel estimation and symbol detection, and it additionally accounts for the statistical prior distributions of the cross-polarization crosstalk coefficients. This avoids an overestimation of these crosstalk coefficients. A practical method for both fast computations and optimal performance is then presented, which allows nonlinear compensation for high-order modulations. Next, we present Monte-Carlo simulations showing that the proposed algorithm performs close to the theoretical limits. Large performance improvement can be obtained and this is particularly emphasized with higher order modulation such as a 16-ary quadrature amplitude modulation. Finally, using Nyquist pulse shaping and polarization-division multiplexed with a quadrature phase-shift keying modulation, the experiments are shown to be in accordance with the simulations and show up to 0.7 dB improvement in Q-factor for the worst-case samples.

DSP power balancing for multi-format WDM receiver

We present a WDM transponder that balances the power between the SD-FEC receiver and the Chromatic Dispersion compensator according to the selected modulation format. Simulations show DSP power gains of 31% at the scale of a continental WDM network.

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).

Multiflow regeneration using network coding for bidirectional links

We propose to implement bit-level network coding with novel multiflow regenerators in bidirectional links. Our regenerators are designed to send two different messages out of a single transmitter. Simulations show an estimated ~20% equipment cost reduction at same performance.

IDEALIST data plane solutions for elastic optical networks

The elastic optical networks paradigm offers a competitive solution in terms of resource utilization to cope with the ever-increasing traffic demand. Specifically, the ability to make a number of previously fixed transmission parameters tunable, for example the data rate or channel spacing, requires an evolution of the node architecture. To fully benefit from elasticity, the data plane should evolve towards a software-defined architecture. In this paper, we report the work carried out in the ICT IDEALIST project and in particular the data plane solutions towards 1Tb/s optical networks with flexgrid and flex-rate technology. Flexibility requires changes in optical cross-connect, transponder as well as in the digital layer. The consortium builds pre-commercial experimental testbeds to validate the proposed building blocks and to analyze candidate applications.

A novel compensation method at the receiver for cross-polarization modulation effects

We propose a novel algorithm mitigating cross-polarization modulation based on a joint blind channel estimation and symbol detection. Using Nyquist pulse shaping and PDM-QPSK modulation, experiments are in accordance with simulations and show up to 0.7 dB improvement in Q-factor.