Silvello Betti

Format conversion of optical data using four-wave mixing in semiconductor optical amplifiers

We present an analysis of the effect of four-wave mixing (FWM) on the pulse propagation in the active region of semiconductor optical amplifiers (SOAs). Our model, based on a rate equation approach, successfully predicts operation of optical data sampling using FWM interaction between a signal bitstream and an optical clock. Such a process can be used for format conversion of optical pulses from nonreturn-to-zero to return-to-zero bitstreams.

Experimental evaluation of modulation induced by continuous waves in a semiconductor optical amplifier

Many simulative approaches have been proposed to investigate Semiconductor Optical Amplifier (SOA) behaviour, in order to model its performance when used in several scenarios. Most of the applications of SOAs are based on the propagation of maximum two signals within the active medium, thus, higher order phenomena due to beating of more than two signals are not always correctly predicted by usual simulative models. In this paper we report some experimental results which validate an accurate model for SOA nonlinearities. This model is based on calculation of nonlinear susceptibility whose expression depends on multicarrier propagation. In particular, three signals are considered and their nonlinear interaction is evaluated by measuring a modulation arising on one of the signals.

Optical Packet Network With Limited-Range Wavelength Conversion: A Novel Formalization of the Optimal Scheduling Problem

In this paper, we consider synchronous optical packet networks formed by switches equipped with a complete set of limited-range wavelength converters. On these networks, we dealt with scheduling algorithm that maximizes the switch throughput. So far, previous literature works have formalized this scheduling problem as the finding of a maximum bipartite matching (MBM) in a convex graph. The MBM formalization has collected various follow-ups, mainly focused on measuring switch-level performance. We revise the MBM formalization by measuring network-level performance. Surprisingly, we find out that when optical switches are cascaded, MBM formalization has two not negligible lacks: (1) a useless degradation of optical signal quality and (2) a tendency of shifting optical packets toward lower wavelengths, thus increasing the occurrence of wavelength contention. To solve these issues, we propose a novel formalization of the scheduling problem as the finding of a MBM with minimum edges weights (MW-MBM). We show that MW-MBM outperforms MBM in terms of both network throughput and optical SNR. Performance evaluation is carried out by means of NS2 simulator that we extend to toughly model optical components (e.g., semiconductor optical amplifier four-wave-mixing wavelength converter). The simulator is provided as open source.

3R all optical regeneration

The authors investigate a possible technique, based on a three stage cascade configuration, in order to implement an all-optical 3R regenerator. A multiwave-mixing based unit is used to perform simultaneously reshaping, re-amplification and wavelength conversion of a propagated signal. A fiber ring based unit is used to perform the all-optical timing extraction while a classical four-wave-mixing process inside a dispersion-shifted fibre is adopted for the retiming process.

Evaluating SOA Nonlinearity Effects by High-Order Susceptibility on Constant Envelope Signals in WDM Systems

Nonlinearity effects, arising within a semiconductor optical amplifier (SOA), have been deeply investigated with particular interest for exploiting them in wavelength conversion. This application shrinks the research area to a precise scenario: a strong pump signal travels through the active medium simultaneously with a modulated signal to be converted. In this case, it is possible to neglect the spectral distribution of the optical power and phase relationship between propagating signals. SOAs have been also studied as line amplifiers for wavelength-division multiplexing (WDM) phase-modulated signals. Aim of this paper is to extend the propagation model in an SOA, in order to simulate nonlinearities occurring in the amplification of a WDM comb signal evaluating-wave mixing on constant envelope modulation schemes (differential phase-shift keying). This can be carried out due to an enhanced analytical model based on the optical field and medium interaction, overcoming the wide-used rate equation approach, which is based on the overall photons density.

Radio-over-Fiber (RoF) Techniques for Broadband Wireless LAN

Radio-over-fiber (RoF) techniques are attractive for realizing high performance integrated networks. The growth of mobile and wireless communications fuels increasing demand for multimedia services with a guaranteed quality of service. This requires realization of broadband distribution and access networks. Within this framework, RoF schemes can be applied for realizing seamless wireless networks since they allow for the easy distribution of microwaves and millimeter waves over long distances along optical fibers. Some of the applications of RoF technology include cellular networks, satellite communications, multipoint video distribution services (MVDS), mobile broadband system (MBS), wireless LANs over optical networks.

Performance evaluation of an all-optical clock recovery and data resampling stage for NRZ data signals

A novel actively modelocked gain-clamped semiconductor optical amplifier based ring scheme able to recover non-return-to-zero formats at 10 Gbit/s data rate is experimentally evaluated in terms of jitter, bit-error-rate and locking time using a deployed cable

Performance Analysis of Underwater Swarm Sensor Networks

Fundamental key aspects of underwater acoustic communications have been taken into account to define an underwater swarm network for monitoring and exploration applications. We discuss the communication architecture of underwater sensor networks as well as the factors that influence underwater network design. Specifically, the main requirements needed to design a suitable sensors underwater system has been provided by considering a Cross-Layer solution among the lower layers of the node to maintain the power consumption as low as possible without complexity addition in the architecture design. Results show that the average power can be preserved thanks to power control implementation used to optimize the overall across the physical, Medium Access Control (MAC) and Network (NWK) layers. This study wants to provide the performance analysis of a swarm network model to provide guideline for hardware developing of swarm nodes for a real underwater application.

HAP-GEO optical links: Performance analysis under weak turbulence conditions

High altitude Platforms represent a very attractive solution to enhance space communications in terms of available capacity and system topology. They can be geared with multi-functional payload, both for communications and Earth Observation missions. Thanks to their opportune position, they are the key for optics and RF technology integration in space communications. In this paper we evaluate the feasibility of an optical HAP-GEO-HAP link over more than 80,000 km above the stratosphere. In particular, we consider a system based on 1550 nm technology, that exploits the potentialities of DPSK modulation format with Direct-Detection balanced interferometer receiver, and optical amplifier.

A novel multimedia-multisensorial 4D platform

With reference to recent experiences in movies targeted to reproduce sensory stimulation (thermal and olfactory) in combination with audio-visual contents, this paper describes a line of research developed aimed at testing a possible integration of multisensorial systems into multimedia streams. In particular, a demonstration 4D platform and its main components are presented by highlighting both their architectural and technological main features. The transport of control signals to the actuators is a crucial point, because one must consider both current standards and possible future developments. Therefore, we identified two strategies for data transport in local systems, first using a single file and then using multiple separate files, and we have analyzed three transmission modes for ancillary data in communication networks in order to select the most appropriate for our application. To encode sensory effects data related to control signals we propose the use of MPEG-V standard.