Filippo Ponzini

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.

Centralized radio access networks over wavelength-division multiplexing: a plug-and-play implementation

The evolution of centralized radio access networks is discussed from a pragmatic perspective, taking into account the network and radio requirements. The use of wavelength-division multiplexing technology to support this evolution is proposed, and the opportunities for network operators in terms of operational cost, energy efficiency, reuse of already deployed infrastructures, and network convergence are discussed.

Transmission solutions and architectures for heterogeneous networks built as C-RANs

A novel end-to-end transport network solution is proposed to meet the operational and technical challenges of heterogeneous networks built as C-RANs with centralized base band processing and CPRI links. The flexibility of the proposed architecture to support distributed architectures and Ethernet links is also described and the results of a C-RAN proof of concept demonstration are discussed. Substantiated by the evolution of key optical technologies, including a novel WDM-PON based solution, we conclude that backhaul and metro network strategies need to flexibly support both centralized and distributed radio baseband solutions, as well as being multiservice capable. Additionally, as a complement to fiber, we propose use of the 70/80 GHz frequency band (E-band) to provide high performance microwave links for both centralized and distributed architectures.

Modeling and measurement of noisy SOA dynamics for ultrafast applications

A complete and effective tool for the analysis of semiconductor optical amplifiers (SOAs) in ultrafast telecommunication applications is presented. This model includes gain dynamics, the current induced gain saturation effect, the current-dependent gain dispersion, and the amplified spontaneous emission. Experimental results concerning both stationary and dynamic conditions confirm the model accuracy and its effectiveness in the design of all-optical signal processing schemes based on SOAs. Finally, we study the characteristic times and the efficiencies of SOA fast dynamics in order to investigate the bandwidth limits of these devices. A numerical evaluation, validated by high-resolution measures makes the SOAs suitable to process optical signals up to 160 Gb/s.

New optical sampler based on TOAD and data postprocessing for subpicosecond pulse resolution

A low-complexity terahertz optical asymmetric demultiplexer-based optical sampler with simple data postprocessing for subpicosecond pulse shape characterization is proposed. Comparisons with commercial instruments demonstrate the accuracy of the implemented scheme reproducing optical pulses with a resolution of few hundreds of femtoseconds. Nevertheless, the proposed technique allows us to go down to femtosecond accuracy, slightly increasing the data postprocessing complexity. A further validation of the proposed optical sampler is numerically provided.

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.

Electrical equivalent model for an optical VCO in a PLL synchronization scheme for ultrashort optical pulse sources

The electrical modeling of complex electrooptical devices is a useful task for the correct design of its schemes and for the estimation of its performance. In this paper, we consider an electrooptical phase-locked loop (PLL) used to synchronize an RF system clock to the repetition rate of an optical pulsed source, realized by an active fiber mode-locking (ML) technique in the regenerative configuration. The synchronization scheme is suggested by a description of the pulsed source, for the first time, as an optical voltage-control oscillator (VCO). In particular, we present a simple new all-electrical model for the proposed optical VCO, and we verify its accuracy by the implementation of the whole PLL scheme at 2.5 and 10 GHz.

Trade-off between power and bandwidth consumption in a reconfigurable xhaul network architecture

The increasing number of wireless devices, the high required traffic bandwidth, and power consumption will lead to a revolution of mobile access networks, which is not a simple evolution of traditional ones. Cloud radio access network technologies are seen as promising solution in order to deal with the heavy requirements defined for 5G mobile networks. The introduction of the common public radio interface (CPRI) technology allows for a centralization in BaseBand unit (BBU) of some access functions with advantages in terms of power consumption saving when switching off algorithms are implemented. Unfortunately, the advantages of the CPRI technology are to be paid with an increase in required bandwidth to carry the traffic between the BBU and the radio remote unit (RRU), in which only the radio functions are implemented. For this reason, a tradeoff solution between power and bandwidth consumption is proposed and evaluated. The proposed solution consists of: 1) handling the traffic generated by the users through both RRU and traditional radio base stations (RBS) and 2) carrying the traffic generated by the RRU and RBS (CPRI and Ethernet flows) with a reconfigurable network. The proposed solution is investigated under the lognormal spatial traffic distribution assumption. After proposing resource dimensioning analytical models validated by simulation, we show how the sum of the bandwidth and power consumption may be minimized with the deployment of a given percentage of RRU. For instance we show how in 5G traffic scenarios this percentage can vary from 30% to 50% according to total traffic amount handled by a switching node of the reconfigurable network.

Future proof optical network infrastructure for 5G transport

The telecommunication community has reached a broad consensus that the current radio access network (RAN) and underlying transport will not be able to scale up to the traffic volume and quality expected in 5G. Thus, it is necessary to remove all the technological bottlenecks and operational rigidities to ensure a painless migration from the existing radio scenario to the 5G one. This article presents a transport architecture able to serve as a backhaul and fronthaul to convey radio traffic on the same optical infrastructure. The cornerstones of the solution are a novel photonic technology used to provide optical connectivity, complemented by a dedicated agnostic framing; a deterministic switching module; and a flexible control paradigm based on a layered scheme and on the slicing concept to facilitate optimal interactions of transport and radio resources while preserving a welldemarcated mutual independence. Simulations and experiments are presented to demonstrate the aforementioned features.