Satellite optical communications will revolutionize global high-speed connectivity. In this paper, we carry out a comprehensive evaluation of end-to-end (E2E) Wavelength Division Multiplexing (WDM)-Free Space Optical Communication (FSOC) systems to establish high-performance Earth-GEO links using a semi-analytical tool. We present a novel method to accurately compute the divergence of a truncated and obscured beam, typical of Cassegrain telescopes; this model is instrumental to optimize the beam divergence with Pointing Error (PE) and beam wander. The effects of beam wander, scintillation, and PE are first individually investigated to derive the required margins for different outage probabilities (OPs), followed by an assessment of Adaptive Optics (AO) benefits and limitations. Furthermore, we comprehensively assess the uplink and downlink systems, exploiting for the first time an innovative and fully analytical closed-form expression to describe the combined three statistical effects. Finally, the full system analysis is carried out in the challenging scenario of strong turbulence, at various elevation angles and OP targets. By considering both coherent and non-coherent systems adopted from fiber communications, we determine the transmitter power and the maximum achievable throughput.

Combining the use of Extremely High Frequencies (EHF) and Free Space Optics (FSO) for the feeder links of future High Throughput Satellites (HTS) is recognized as a key element to optimize system efficiency in terms of costs, power consumption and to increase the data rate to unprecedented levels (Terabit/s). This paper provides an overview of the main challenges to be faced to make the exploitation of hybrid EHF/FSO links feasible and cost-effective. In this framework, propagation and HW impairments mitigation techniques will play a key role. Therefore, the paper also presents a vision on how the use of SDN/SDR and NFV, extended down to lower layers of the protocol stack, could provide novel, so far unexplored, opportunities for optimizing the performance of such mitigation techniques.

Marine researchers and operators during their daily work need consistent data from the underwater environment to constantly monitor the habitat's probes and the robots condition. For underwater applications, wireless communication is of paramount importance. Today, the needs for high-speed communication has prompted the exploration of the Underwater Optical Wireless Communications (UOWCs) method. This paper presents the design and validation aspects of the optical layer of a bidirectional UOWC system developed in the framework of the European Project SUNRISE, able to provide wireless connectivity compliant to 10Base-T Ethernet protocol (Manchester-coded signal with 10 Mb/s data rate). The designed modems are made of two similar optical transceivers, each including a transmitter, a receiver unit, and an optical power monitor part. The transmitter is based on an array of blue Light Emitting Diodes; the receiver exploits a commercially available Avalanche Photodiode (APD) and the monitoring relies on a pin-photodiode. The modems, after a deep characterization in controlled environments, were proved to work with the required 10Base-T Ethernet, up to 7.5 m distance in shallow harbor waters. The complete optical system is intended to become a node of the SUNRISE infrastructure.

Vehicular Communication Systems are an emerging type of networks in which vehicles and roadside units are the communicating nodes, providing each other with information, such as safety warnings and traffic information. Vehicle-to-vehicle message exchange is considered the preferred pattern for safety-critical communication (e.g. in anti-collision active systems). Recently, LED-based optical wireless communication has been also proposed for car to car message delivery. This option turns to be particularly effective in short range direct communications to exploit its line-of-sight feature and overcome the issues related to the isotropic nature of radio waves. In this paper we experimentally address this case study making use of two low cost On-Board Unit prototypes, equipped with a common Light Emitting Diode (LED) component at the transmitter and a common PIN photodiode at the receiver.

We review a novel free space optical (FSO) system that represents a significant breakthrough in the area of FSO communications. The system encompasses a pair of novel terminals: these allow direct and transparent optical connection to common single mode fibers and include a dedicated electronic control unit that effectively tracks the signal beam wandering due to atmospheric turbulence and mechanical vibrations. Further improvement in the signal power stabilization is achieved by means of saturated EDFAs. These solutions allow to realize a new FSO system, which is tested in a double-pass FSO link between two buildings in Pisa, Italy. When the terminals are fed by common WDM signals they allow enough power budget and margins to support a record high capacity transmission (32times40 Gbit/s), with a enormous improvement of stability (six hours with no error burst). During day-long transmission, the system behavior has been deeply characterized to correlate any increase of bit error ratio (BER) to the FSO control parameters.

The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N/spl times/10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4/spl times/4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s.