Lasers for Satellite Uplinks and Downlinks

The article of record as published may be found at http://dx.doi.org/10.3390/sci2030071The use of Light Amplification by Stimulated Emission of Radiation (i.e., LASERs or lasers) by the U.S. Department of Defense is not new and includes laser weapons guidance, laser-aided measurements, even lasers as weapons (e.g., Airborne Laser). Lasers in support of telecommunications is also not new. The use of laser light in fiber optics shattered thoughts on communications bandwidth and throughput. Even the use of lasers in space is no longer new. Lasers are being used for satellite-to-satellite crosslinking. Laser communication can transmit orders-of-magnitude more data using orders-of-magnitude less power and can do so with minimal risk of exposure to the sending and receiving terminals. What is new is using lasers as the uplink and downlink between the terrestrial segment and the space segment of satellite systems. More so, the use of lasers to transmit and receive data between moving terrestrial segments (e.g., ships at sea, airplanes in flight) and geosynchronous satellites is burgeoning. This manuscript examines the technological maturation of employing lasers as the signal carrier for satellite communications linking terrestrial and space systems. The purpose of the manuscript is to develop key performance parameters (KPPs) to inform U.S. Department of Defense initial capabilities documents (ICDs) for near-future satellite acquisition and development. By appreciating the history and technological challenges of employing lasers rather than traditional radio frequency sources for satellite uplink and downlink signal carrier, this manuscript recommends ways for the U.S. Department of Defense to employ lasers to transmit and receive high bandwidth, large-throughput data from moving platforms that need to retain low probabilities of detection, intercept, and exploitation (e.g., carrier battle group transiting to a hostile area of operations, unmanned aerial vehicle collecting over adversary areas). The manuscript also intends to identify commercial sector early-adopter fields and those fields likely to adapt to laser employment for transmission and receipt.U.S. Air Forc

Ethernet Networks for Real-Time Use in the ATLAS Experiment

Ethernet became today's de-facto standard technology for local area networks. Defined by the IEEE 802.3 and 802.1 working groups, the Ethernet standards cover technologies deployed at the first two layers of the OSI protocol stack. The architecture of modern Ethernet networks is based on switches. The switches are devices usually built using a store-and-forward concept. At the highest level, they can be seen as a collection of queues and mathematically modelled by means of queuing theory. However, the traffic profiles on modern Ethernet networks are rather different from those assumed in classical queuing theory. The standard recommendations for evaluating the performance of network devices define the values that should be measured but do not specify a way of reconciling these values with the internal architecture of the switches. The introduction of the 10 Gigabit Ethernet standard provided a direct gateway from the LAN to the WAN by the means of the WAN PHY. Certain aspects related to the actual use of WAN PHY technology were vaguely defined by the standard. The ATLAS experiment at CERN is scheduled to start operation at CERN in 2007. The communication infrastructure of the Trigger and Data Acquisition System will be built using Ethernet networks. The real-time operational needs impose a requirement for predictable performance on the network part. In view of the diversity of the architectures of Ethernet devices, testing and modelling is required in order to make sure the full system will operate predictably. This thesis focuses on the testing part of the problem and addresses issues in determining the performance for both LAN and WAN connections. The problem of reconciling results from measurements to architectural details of the switches will also be tackled. We developed a scalable traffic generator system based on commercial-off-the-shelf Gigabit Ethernet network interface cards. The generator was able to transmit traffic at the nominal Gigabit Ethernet line rate for all frame sizes specified in the Ethernet standard. The calculation of latency was performed with accuracy in the range of +/- 200 ns. We indicate how certain features of switch architectures may be identified through accurate throughput and latency values measured for specific traffic distributions. At this stage, we present a detailed analysis of Ethernet broadcast support in modern switches. We use a similar hands-on approach to address the problem of extending Ethernet networks over long distances. Based on the 1 Gbit/s traffic generator used in the LAN, we develop a methodology to characterise point-to-point connections over long distance networks. At higher speeds, a combination of commercial traffic generators and high-end servers is employed to determine the performance of the connection. We demonstrate that the new 10 Gigabit Ethernet technology can interoperate with the installed base of SONET/SDH equipment through a series of experiments on point-to-point circuits deployed over long-distance network infrastructure in a multi-operator domain. In this process, we provide a holistic view of the end-to-end performance of 10 Gigabit Ethernet WAN PHY connections through a sequence of measurements starting at the physical transmission layer and continuing up to the transport layer of the OSI protocol stack

ARRAY BASED FREE SPACE OPTIC SYSTEM FOR TACTICAL COMMUNICATIONS

Free-space optical (FSO) communications offer a resilient and flexible alternative communications medium to current radio technologies, which are increasingly threatened by our peer adversaries. FSO provides many advantages to radio technologies, including higher bandwidth capability and increased security through its low probability of detection (LPD) and low probability of interception (LPI) characteristics. However, current FSO systems are limited in range due to line-of-sight requirements and suffer loss from atmospheric attenuation. This thesis proposes the use of arrayed optical emitters for FSO communication by developing a link-layer protocol that leverages the inherent error correction of quick response (QR) encoding to increase bandwidth and overcome atmospheric loss. Through the testing of a system built with commercial-off-the-shelf equipment and a survey of current optical transmitter and receiver technology, this link-layer protocol was validated and estimated to provide similar data rates to current single emitter FSO systems. Various limitations were discovered in the current structure of the protocol. Future work should be conducted to correct inefficiencies in the QR encoding format when applied to a transmission medium. Additionally, technological advancements in hardware systems, including the large-scale production of VCSELs and faster high-speed cameras, must be achieved before such an FSO would be viable for large-scale use.http://archive.org/details/arraybasedfreesp1094559655Captain, United States Marine CorpsApproved for public release; distribution is unlimited

Quantum and classical optical channels Coexistence in optical Access Networks

Η διατριβή αυτή ερευνά τη συνύπαρξη της Διανομής Κβαντικών Κλειδιών (QKD) με κλασικά κανάλια σε οπτικά δίκτυα πρόσβασης. Η εισαγωγή παρέχει μια επισκόπηση του θέματος και στη συνέχεια ακολουθεί μια σύνοψη των αρχών της κβαντικής μηχανικής και των διαδικασιών που εφαρμόζονται στην κβαντική διανομή κλειδιών. Συζητούνται κάποια πρωτόκολλα QKD, συμπεριλαμβανομένων των ΒΒ84 και ΒΒ84 με decoy καταστάσεις. Η διατριβή εξετάζει επίσης την επίδραση μη γραμμικών φαινομένων, όπως η σκέδαση Raman, ο θόρυβος που προκαλείται απο την παρουσία πολλαπλών κυμάτων , καθώς και γραμμικών φαινομένων, όπως η ανάκλαση Rayleigh και η χρωματική διάσπορά. Μετά την ανάλυση των θεωρητικών προαπαιτούμενων, παρέχεται μια σύνοψη των προηγούμενων ερευνών για τη συνύπαρξη του QKD με κλασικά κανάλια. Επιπλέον, περιλαμβάνεται η πειραματική διαδικασία που αποτελείται από δύο μέρη. Το πρώτο μέρος περιλαμβάνει μια έρευνα που γίνεται στο εργαστήριο οπτικής. Πιο συγκεκριμένα μελετώνται οι αλληλεπιδράσεων όταν δύο ζεύγη μηχανημάτων Toshiba που υλοποιούν το πρωτόκολλο BB84 με decoy states τοπόθετούνται σε φορά αντίθετης διάδοσης καθώς και η συνύπαρξη αυτής της τοπολογίας με κλασσικά κανάλια. Τέλος, το δεύτερο μέρος παρουσιάζει την πρακτική εφαρμογή της συνύπαρξης των κβαντικών καναλιών θέτοντας σε λειτουργία τον εξοπλισμό της Toshiba στην προσομοίωση του GPON δικτύου της COSMOTE που βρίσκεται στο OTE Academy.This master thesis explores the coexistence of Quantum Key Distribution (QKD) with classical channels in optical access networks. The introduction provides an overview of the topic, followed by an overview of the principles of quantum mechanics and QKD procedures. Various QKD protocols, including BB84and BB84 Decoy State are discussed. The thesis also investigates the impact of nonlinear effects such as Raman scattering and four-wave mixing, as well as linear effects like Rayleigh back-scattering and chromatic dispersion on the coexistence of QKD with classical channels. After having discussed the theoretical background the thesis provides a synopsis of prior research on the coexistence of QKD with classical channels. Furthermore there is an experimental procedure which consists of two parts. The first part involves an investigation of counter-propagating interactions in quantum communications using two pairs of Toshiba machines which implement the BB84 protocol with decoy states and also the coexistence of counter-propagating interactions with classical channels . Finally the second part presents the practical deployment of QKD coexistence over GPON replica located at OTE Academy

Modelling and Design of Resilient Networks under Challenges

Communication networks, in particular the Internet, face a variety of challenges that can disrupt our daily lives resulting in the loss of human lives and significant financial costs in the worst cases. We define challenges as external events that trigger faults that eventually result in service failures. Understanding these challenges accordingly is essential for improvement of the current networks and for designing Future Internet architectures. This dissertation presents a taxonomy of challenges that can help evaluate design choices for the current and Future Internet. Graph models to analyse critical infrastructures are examined and a multilevel graph model is developed to study interdependencies between different networks. Furthermore, graph-theoretic heuristic optimisation algorithms are developed. These heuristic algorithms add links to increase the resilience of networks in the least costly manner and they are computationally less expensive than an exhaustive search algorithm. The performance of networks under random failures, targeted attacks, and correlated area-based challenges are evaluated by the challenge simulation module that we developed. The GpENI Future Internet testbed is used to conduct experiments to evaluate the performance of the heuristic algorithms developed

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics