Gianmarco Bruno

Efficient label encoding in segment-routing enabled optical networks

The currently standardized GMPLS protocol suite for packet over optical networks relies on hierarchical instances of signaling sessions. Such sessions have to be established and maintained also in transit nodes, leading to complex and weighty control plane implementations. A novel technology called Segment Routing (SR) has been recently proposed to address these issues. SR relies on the source routing paradigm to provide traffic engineering solutions. In particular, the computed route for a given request is expressed as a segment list applied as an header to data packets at the ingress node. Specific algorithms are then required to perform the path computation and express the computed path through an effective segment list encoding (i.e., label stack), minimizing the segment list depth (SLD) (i.e., the number of labels included in the segment list). So far, no algorithms have been proposed to jointly provide path and segment list computation in SR-based networks. In this study, an efficient segment list encoding algorithm is proposed, guaranteeing optimal path computation and limited SLD in SR-based networks. The algorithm also accounts for equal-cost multiple paths and multiple constraints. The proposed algorithm is successfully applied to different network scenarios, demonstrating its flexibility in several use cases and showing effective performance in terms of segment list depth and introduced packet overhead.

Beyond 100Gbit/s: System implications towards 400G and 1T

400G and 1Tbit/s optical transmission will surely benefit from the advances in modulation techniques developed for 100Gbit/s. However, it is required a profound system re-thinking to realize transmission beyond 100G over long-haul wavelength-switched networks.

Experimental Analysis of the Power Auto-Correlation-Based Chromatic Dispersion Estimation Method

We experimentally investigate the performance of the signal power autocorrelation-based method for chromatic dispersion (CD) estimation in a polarization-multiplexing quadrature phase-shift keying (PM-QPSK) 100G coherent optical system conveying optical channel transport unit level-4 (OTU4) frames. It is shown that the typical laboratory setup, where the signal components are generated from delayed versions of the same pseudorandom binary sequence (PRBS), is inadequate for experimental validation because of artifacts in the signal auto-correlation function. This problem is circumvented by the use of a commercial line card transporting independent data sequences. The algorithm is used to estimate accumulated CD values from 0 to 50 000 ps/nm under up to 80-ps differential group delay (DGD). We further evaluate its convergence properties in terms of the length of the sample vector required for correct CD estimation and address the hardware resource requirements. The CD-shifted version of the algorithm yielded a maximum estimation error of 186 ps/nm in all tested conditions.

Path Encoding in Segment Routing

Segment Routing (SR) is emerging as an innovative traffic engineering technique compatible with traditional MPLS data plane. SR relies on label stacking, without requiring a signaling protocol. This greatly simplifies network operations in transit nodes. However, it may introduce scalability issues at the ingress node and packet overhead. Therefore, specific algorithms are required to efficiently compute the label stack for a given path. This study proposes two algorithms for SR label stack computation of strict routes that guarantee minimum label stack depth. Then, SR scalability performance is investigated. Results show that, in most of the cases, SR uses label stacks composed of few labels and introduces a limited packet overhead. However, relevant scalability issues may arise in specific cases, e.g., large planar topologies.

High power, narrow linewidth, low noise, integrated CMOS tunable laser for long haul coherent applications

An integrated-CMOS-tunable-laser with 15-dBm output power is presented. Fabrication is realized in commercial CMOS foundry. Laser shows high power, low RIN, and ultra-narrow linewidth. Performance over fiber is comparable with best-in-class, market-leading ITLA, proving suitability for long haul coherent applications.

Nonlinear tolerance of 112-Gb/s DP-QPSK in a live field upgrade trial over a 848km 10G DWDM link

An in-service field trial with coherently detected DP-QPSK at 112 Gb/s was performed over a Telefónica live link of 848km, testing long term stability and determining noise margin and optimum launch power of the format.

Cognitive power management in 100G optical transponders

We propose a scheme for efficient power control in 100G optical transponders through reduction of the length of electronic chromatic dispersion compensation filters, according to the network traffic fluctuations. Transmission rate reduction is achieved by symbol retransmission, while maintaining system parameters unchanged, to avoid increased complexity. Power savings offered by the scheme are estimated.

Scalable approaches for path computation

Optimal and fast approaches for path computation are of paramount importance especially for the path computation elements (PCE) of generalized multi-protocol label switching (GMPLS) networks. To overcome the computational complexity, optimality must be traded for the execution time, enabling scalable computation. This paper considers the typical routing problems addressed by PCE and compares different optimization approaches based on integer linear programming (ILP) formulation and its relaxation, with the objective of assessing optimality and scalability of the approaches.

Flexible-sense optical transmission

We present a platform for the optical interconnection of traffic nodes where the sense of transmission is exploited as an additional degree of flexibility. Implementation of the optical arrangement is shown. The requirements about the negotiation of the available resources, such as fibers and wavelengths, are discussed. We evaluate the implications of flexible-sense transmission in terms of cost, power and reach, under realistic assumptions of traffic peak-to-average bandwidth ratio and degree of asymmetry.

Evolutions of a pan-european network over truewave-RS fiber enabled by flexible grid and coherent detection

We investigate possible evolutions of an optical backbone over TrueWave-RS. Maximum inter-capital capacity is obtained with fixed-grid 50-GHz spaced DP-QPSK 100G wavelengths when the interplay between spectral efficiency and XPM is considered.