Fabio Cavaliere

Modeling and Distributed Provisioning in 10–40–100-Gb/s Multirate Wavelength Switched Optical Networks

In wavelength-switched optical networks (WSONs), quality of transmission (QoT) has to be guaranteed during lightpath provisioning. In multibit-rate WSONs, this task is complicated by the coexistence of optical connections operating at different bit-rates and modulation formats. The major issue consists in accounting for the severe impairments due to cross-phase modulation (XPM) induced by 10 Gb/s lightpaths on neighbor 40 or 100 Gb/s lightpaths. In this paper, QoT modeling is first reviewed for 10, 40, and 100 Gb/s transmission according to the adopted modulation format and detection type. In addition, a Gaussian approximation to compute the bit error rate of differential quadrature phase-shift keying (DQPSK) and QPSK signals is proposed, as well as closed formulas to compute the nonlinear phase noise variance due to XPM. Also, discussions about the XPM cumulation over spans in a WSON and how XPM can be considered in a dynamic network are provided. Then, four lightpath provisioning schemes are proposed to effectively account for QoT and, in particular, for XPM. The schemes differently exploit: 1) augmented spectral separation among lightpaths at different bit rates; 2) XPM worst-case scenario; and 3) current and novel generalized multiprotocol label switching extensions. The performance of the proposed schemes is evaluated through simulations in several multibit-rate scenarios. Results show that the proposed schemes provide effective network resource utilization while guaranteeing the adequate QoT to lightpaths at any bit rate.

Xhaul: toward an integrated fronthaul/backhaul architecture in 5G networks

The Xhaul architecture presented in this article is aimed at developing a 5G integrated backhaul and fronthaul transport network enabling flexible and software-defined reconfiguration of all networking elements in a multi-tenant and service-oriented unified management environment. The Xhaul transport network vision consists of high-capacity switches and heterogeneous transmission links (e.g., fiber or wireless optics, high-capacity copper, mmWave) interconnecting remote radio heads, 5G points of attachment (5GPoAs, e.g., macro- and small cells), centralized- processing units (mini data centers), and points of presence of the core networks of one or multiple service provider(s). This transport network shall flexibly interconnect distributed 5G radio access and core network functions, hosted on network centralized nodes, through the implementation of a control infrastructure using a unified, abstract network model for control plane integration (Xhaul Control Infrastructure, XCI); and a unified data plane encompassing innovative high-capacity transmission technologies and novel deterministic-latency switch architectures (Xhaul packet Forwarding Element, XFE). Standardization is expected to play a major role in a future 5G integrated front haul/backhaul architecture for multi-vendor interoperability reasons. To this end, we review the major relevant activities in the current standardization landscape and the potential impact on the Xhaul architecture.

Evolution Scenario Toward WDM-PON [Invited]

In this paper we present and critically discuss different wavelength division multiplexing passive optical network (WDM-PON) architectures compatible with pre-existing gigabit PON (GPON) infrastructures. The concurrent use of the trunk fiber permits a hitless evolution from an existing time division multiplexing optical access network to a point-to-point wavelength division access network. System performance has been experimentally evaluated in terms of bit error rate.

Rethinking Optical Transport to Pave the Way for 5G and the Networked Society

The fifth generation of mobile networks (5G) is the next major phase of mobile telecommunications, which will provide the foundation for the Networked Society. To support 5G, transport will need to cater for a wide range of service requirements. It will need to support emerging 5G radio systems in terms of higher capacity and increasing number of cell sites. It must also cater for increasing need for radio interference coordination between sites as well as cost effective radio access network deployment models, and provide a flexible platform for sharing of resources where different actors through transport application programming interfaces have access to network resources and diverse transport services. In this paper, we summarize the key defining factors for 5G transport and outline a concept for programmable transport based on WDM and exploiting emerging optical devices enabled by integrated photonics.

Casting 1 Tb/s DP-QPSK communication into 200 GHz bandwidth

We demonstrate the feasibility of a novel time-frequency packing technique to implement DP-QPSK communication with a record spectral efficiency ranging from 5.14 to 4.3 bit/s/Hz over a distance ranging from 3000 km to 5200 km of uncompensated standard fiber, respectively.

Optical Time–Frequency Packing: Principles, Design, Implementation, and Experimental Demonstration

Time-frequency packing (TFP) transmission provides the highest achievable spectral efficiency with a constrained symbol alphabet and detector complexity. In this paper, the application of the TFP technique to fiber-optic systems is investigated and experimentally demonstrated. The main theoretical aspects, design guidelines, and implementation issues are discussed, focusing on those aspects which are peculiar to TFP systems. In particular, adaptive compensation of propagation impairments, matched filtering, and maximum a posteriori probability detection are obtained by a combination of a two-dimensional equalizer and four eight-state parallel Bahl-Cocke-Jelinek-Raviv (BCJR) detectors. A novel algorithm that ensures adaptive equalization, channel estimation, and a proper distribution of tasks between the equalizer and BCJR detectors is proposed. A set of irregular low-density parity-check codes with different rates is designed to operate at low error rates and approach the spectral efficiency limit achievable by TFP at different signal-to-noise ratios. An experimental demonstration of the designed system is finally provided with five dual-polarization QPSK-modulated optical carriers, densely packed in a 100-GHz bandwidth, employing a recirculating loop to test the performance of the system at different transmission distances.

5G-Crosshaul: An SDN/NFV control and data plane architecture for the 5G integrated Fronthaul/Backhaul

This paper presents the control and data plane architecture design for a 5G transport solution 5G-Crosshaul with the aim of integrating the fronthaul and backhaul network segments in a common transport stratum. The control plane relies on the Software-defined networking/Network Functions Virtualization concept to control and orchestrate the different elements of the network the 5G-Crosshaul control infrastructure. The data plane is based on an mixed optical/packet-based forwarding entity the 5G-Crosshaul forwarding element that leverages the benefits of optical passthrough with the statistical multiplexing of packet-based transmission, working on top of a common frame format for both, fronthaul, and backhaul traffic the 5G-Crosshaul common frame. In addition to the main architecture design, this work includes the impact of providing multi-tenancy support into the architecture of the overall system, in order to share the costs of building and operating the infrastructure among different operators.

Colorless WDM-PON Architecture for Rayleigh Backscattering and Path-Loss Degradation Mitigation

The effectiveness of colorless performance- improved wavelength-division-multiplexing passive optical networks (PONs) compatible with gigabit-PON is presented. The proposed solution is based on a service optical network unit (service-ONU) for multiwavelength distribution. Mitigation of Rayleigh backscattering effect and path-loss degradation is demonstrated in 2.5- and 10-Gb/s reflective schemes employing reflective semiconductor-optical- amplifier and reflective electroabsorption modulator at the ONU.

Migration towards high speed optical access enabled by WDM techniques

Different options for the evolution of a WDM PON toward 10 Gb/s channel rate are compared and experimentally investigated. Although today 10 Gb/s is not yet cost effective for a fiber access network, it can become a viable option in the next years, pushed by the demand of new, bandwidth hungry services and enabled by recent technology advancements.

Analysis of Crosstalk in Mixed 43 Gb/s RZ-DQPSK and 10.7 Gb/s DWDM Systems at 50 GHz Channel Spacing

In DWDM field experiments over 1047 km of standard fiber and in simulations we analyze the impact of crosstalk on a 43 Gb/s RZ-DQPSK channel both by 10.7 Gb/s OOK and 43 Gb/s RZ-DQPSK neighbors at 50 GHz channel spacing.