G. Incerti

Free Space Optical Technologies

Free Space Optics (FSO), also known as Optical Wireless or Lasercom (i.e. Laser Communications), is a re-emerging technology using modulated optical beams to establish short, medium or long reach wireless data transmission. Most of the attention on FSO communication systems it was initially boost by military purposes and first development of this technology was dedicated to the solution of issues related to defense applications. Today’s market interest to FSO refers to both civil and military scenarios covering different situations and different environments, from undersea to space. In particular, due to the high carrier frequency of 300 THz and the consequently high bandwidth, the most prominent advantage of Free Space Optical (FSO) communication links may be their potential for very high data rates of several Gbps (up to 40 Gbps in the future (J. Wells, 2009)). Other advantages like license-free operation, easy installation, commercial availability, and insensitivity to electromagnetic interference, jamming, or wiretapping make FSO interesting for applications like last mile access, airborne and satellite communication (L. Stotts et alt, 2009), temporary mobile links and permanent connections between buildings. Mainly, the adoption of FSO is needed when a physical connection is not a practicable solution and where is requested to handle an high bandwidth. As a matter of fact, FSO is the only technology, in the wireless scenario, able to grant bandwidth of several Gigabits per second. The interest in this technology is also due to the low initial CAPEX (Capital Expenditure) requirement, to the intrinsic high-level data protection & security, to the good flexibility and great scalability innate in this solution. For these reasons FSO possible applications cover today, as mentioned, a wide range. Thus this technology generates interest in several markets: the first/last mile in dense urban areas, network access for isolated premises, highspeed LAN-to-LAN (Local Area Networks) and even chip-to-chip connections, transitional and temporary network connection, undersea and space communication. Furthermore FSO can be used as an alternative or upgrade add-on to existing wireless technologies when the climatic conditions permit its full usage. 13

Network Performance Investigation in a Wide Area Gigabit Ethernet Test Bed Adopting All-Optical Wavelength Conversion

We experimentally investigate the network performance of a wide area gigabit Ethernet test bed in which we introduced the all-optical wavelength conversion (WC) process. Such a test bed is configured to implement a quality of service (QoS) control based on the virtual private local area network service (VPLS), a technique that, according to the reported results, is well suitable to implement forwarding process based on dedicated wavelengths. We show that the all-optical WC does not degrade the QoS properties of the VPLS and it can be used with very fast switching time.

Experimental Investigation of Quality of Service in an IP All-Optical Network Adopting Wavelength Conversion

We experimentally show how the virtual private large-area network service (VPLS) technique, a layer 2 service, can improve optical network performance in terms of quality of service (QoS), and how a VPLS network behaves when it adopts all-optical wavelength conversion (AOWC), a new optical process that will be introduced in future optical networks. The advantages of VPLS are based on the capability to generate logical reliable paths in each wavelength channel, permitting suitable partitioning of the bandwidth according to the user requirements. In particular, we show the advantages of VPLS in access networks based on passive optical networks, and we test QoS properties of VPLS paths when an AOWC process occurs both in the core and in the access networks. The experimental investigation is carried out in a wide-area, all-optical gigabit Ethernet testbed with an access section based on an Ethernet passive optical network. As far as the core segment is concerned, we chose a high-efficiency AOWC process based on four-wave mixing in dispersion-shifted fiber; conversely in the access segment we chose a cheaper AOWC process based on cross gain modulation in a semiconductor optical amplifier. The reported results show that gigabit Ethernet transmission, with the relative layer 2 techniques, is also well suitable for wide-area WDM architectures, and in particular it is able to guarantee end-to-end QoS for huge bandwidth services such as high-definition TV and also in the case of congestion, restoration, and wavelength conversion processes.

Experimental implementation of an IPTV architecture based on Content Delivery Network managed by VPLS technique

This work aims to shows how to use the base principles of a CDN (Content Delivery Network) to deliver Video Content through Open Internet for VoD (Video on Demand) service through a managed network to improve the reliability and to reduce the degradation due to congestion in the backbone area. The managed network is achieved by means of the VPLS (Virtual Protocol Lan Service) technique that allows the CDN to take advantages from features of a fast restoration in case of node or link failure and the Transport Engineer for the best Path.

Optical fiber bending limits for optical fiber infraestructures

In this work the high power propagation in tight bent fibers was studied. The signal losses and the temperature increase have been experimental measured for single mode optical fibers (SMF) as function of the bending diameter. These results were used to propose an approach to limit the bending diameter, as a function of the injected power, in order to maintain the operational condition bellow the safety limit.

Reducing Complexity and Consumption in Future Networks

The authors report the main results of the EU FP7 SARDANA project, a future network architecture able to provide large bandwidth to the end user in a flexible and intelligent way. The remote amplification for network reach extension, the remote monitoring of the network infrastructure, and the possibility of remotely powering ONUs are fundamental capabilities to maintain the passiveness of the network outside plant, so important for reducing power consumption and maintenance costs, without compromising network reach and coverage.

Transience analysis of bursty traffic with erbium Doped Fiber Amplifiers

In this paper, we investigate experimentally the impact of optical amplifiers, namely Erbium Doped Fiber Amplifiers (EDFA) on Optical Burst Switching (OBS) networks, operating at 2.5 Gb/s (typical bit rate for current passive optical networks - PON). Bursts with 212 – 1 and 216 – 1 pseudo random binary sequence (PRBS) were studied, with different idle times (from 2µs to 80 µs). The use of traffic with variable idle time was assessed in order to evaluate the effect on the burst initial amplitude. We also analyzed the performance of the packet based system by measuring the Q factor at the receiver and concluded that the performance is not affected by the type of traffic (variable or fixed idle times).

All Optical Multichannel Regeneration Systems Based on Non Linear Effects

Summary form only given. In order to increase the performances of the today DWDM backbone networks the simultaneously elaboration of more channels is request. New optical regeneration multichannel systems, based on non linear effects, exploit the optical medium properties to perform frequency convert and noise signal compression. Four wave mixing (FWM), as non linear effect in standard silica fibres and photonic crystal fibres, can be advantageously used to implement these new devices.

All-optical multi-wavelength devices for ultrafast WDM signal processing

In this paper, the authors present results based on a 2R (re-amplification and re-shaping) multiwavelength regeneration system, with wavelength conversion capabilities. In a counter propagation approach, the system is able to regenerate several end user data stream at the same time opening the way to efficient wavelength allocation, network congestion reduction and QoS enhancement in the wide area optical network segment. A short review on the state of the art will be presented too.

Remote pumping and signalling in a passive optical network scenario

In this paper we study the possible amplification architecture for passive optical network, in particular we study the interaction of different amplification system. We also propose a novel scheme to implement a signalling channel by direct modulation of the pumping signal.