ATM is based on the efforts of the ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard. It was originally conceived as a high-speed transfer technology for voice, video, and data over public networks. The ATM Forum has broadened the ITU-T�s vision of ATM for extended use over public and private networks, multi-protocol support and mobile ATM. There are also some ATM applications in High Performance Computing (HPC). ATM is a packet switching technique based on a virtual circuit mechanism. Data flows are statistically multiplexed and communication resources are dynamically shared. Therefore the high performance ATM switch is essential for quality of services (QoS). This thesis introduces typical ATM switch architecture design and analyses design problems. The research objective is to propose a switch architecture design that can solve or improve those existing problems to achieve a superior performance. The research goal is an integrated ATM switch architecture that will handle both unicast and multicast packets. Unlike the usual design for the multicast ATM switch which concentrates on a cell copy network with a unicast switching network, the proposed switch architecture processes the network packets in a single switching block, and allows unicast and multicast packets to co-exist without competing. The switch design has a simple topology and operation principle and is easy to implement. Furthermore, no copy network is required. Three major components are proposed to form the core of the new switch architecture: the parallel buffering strategy for improved buffer performance, the fast table lookup algorithm for packet duplication and routing, and the relay ring controller for solving the contention problem associated with multiple packets destined for the same output port. A mathematical model is presented and its numerical results are analysed. In addition, the simulation algorithms for the proposed switching design are presented and compared against the switching design with input and output buffering strategies. The simulation results are also compared and analysed against the numerical results. A multicast traffic model is also presented. Its performance calculation for the proposed switch is achieved through simulation. Performance analysis is compared against the output buffering switch under the same multicast traffic model. The performance analysis shows that the proposed switch architecture achieves high throughput with low cell loss rate and low time delay. Its performance can be as good as the output buffering strategy or better. Therefore the proposed switch design has solved the problems associated with input and output buffering. This thesis also analyses the complexity of the proposed switch architecture and suggests a topology to build a large scale ATM switch. The suitability and feasibility for production implementation are also addressed.

The purpose of this thesis is to develop a high power, compact all solid-state blue laser, which is applicable in micro machining, LIDA, underwater ranging, biochemical techniques and so forth. The passive Q-switching technique, which is known to be a low-cost and simple method to raise the laser peak power was employed in this thesis. In the mean time, the intracavity-doubling technique was integrated to achieve the non-linear frequency conversion for generating blue laser at low cost. Based on our research finding, the reabsorption loss due to thermal effect and a paucity of suppression at wavelength of 1064 nm on laser mirrors could cause the four-level oscillation at 1064 nm instead of three-level oscillation at 914nm. Improvement in heat dissipating system, and suppression at wavelength of 1064 nm on mirror coating has led to a success in developing a quasi-three-level blue laser with peak power of 114W at wavelength 473 nm. A modified rate equation model of the quasi-three level passively Q-switched blue lasers was developed as well, in which the influence of the re-absorption loss in the gain medium and its intracavity frequency doubling were both considered. The influence of reabsorption loss upon the laser power deduction was studied by numerical simulation in order to optimize the laser performance.

No description available.

Today's companies are growing in a steady pace, with more and more network devices added to the network it is very important to keep track of and monitor the status of devices. Even though the wireless evolution has come, it all depends on the wired connections to supply a continuous connection to the rest of the world.   This thesis explores, tests and informs about creating a functional system that automatically creates backups of configuration files from network devices and how to troubleshoot networking problems and maintain a network to keep it in good shape.   Even though many companies have manual backups of router and switch configurations, the possibility to have this part automated should be desired by most companies. It can open up for the administrators in the company to have more time over to help the employees that are experiencing problems at the same time as the automated system eliminates the possible errors that a human can cause. Of course one can see it the other way, that it takes away manual labor for the employees, but it is just a small part of the job yet it is so very important that making this service automated is a good choice for a company. Integrity is proven by the means of backups and by the option to see the difference between the previous backups and the most recent.   The three of us have worked as a group to do all tests and to write the documentation. After working with a couple of companies it is clear that well functional backup systems of network devices are not as common as it should be. Companies that do take backups of the network devices often do this manually. When seeing this it makes sense to use a reliable system that uses revision handling so it is easy to see the recent changes made to the devices.   The results ended up in a working automated backup system for routers and switches. The automated system is running Debian and connects to all the routers and switches in the network to collect the configuration files with the help of rancid. The thesis also explains the functions of concepts such as disaster recovery and different maintenance models.

This report intends to impart a good understanding of routing modules used in modern transceiver systems. The radar system at RadarBolaget AB needed to have a good routing module for its newly designed transceiver antenna. In this report, studies have been done related to two majorly used routing modules in modern electronics industry; Microwave Circulator and RF/Microwave Switch. First off, different characteristics of routing modules are discussed. After having discussed important design parameters, practical design considerations for two routing modules are presented in a profound way. Theoretical knowledge for both of these two devices is presented in the beginning, followed by their practical designs using standard simulation software like HFSS and ADS. The report concludes its findings in a way that at the end of this report, reader becomes acquainted with ample information to be able to choose the best option available among all of the discussed designs. An FET RF Switch is chosen at the end of this project to be used for transceiver system which should be able to satisfy specifications specified by RadarBolaget AB. This project was carried out by two students of Master Program in Electronics/Telecommunications at Högskolan i Gävle in collaboration with RadarBolaget AB, Gävle, Sweden.

No description available.

The design and analysis of a novel optical-to-microwave transducer based upon direct optical control of microwave gallium arsenide (GaAs) field-effect transistor (FET) switches is the subject of this thesis. The switch is activated by illuminating the gate depletion region of the FET device with laser light having a photon energy and wavelength appropriate to the generation of free carriers (electron-hole pairs) within GaAs. The effects of light on the DC and microwave properties of the GaAs FET are explored and analyzed to permit the characterization of the switching performance and transient response of a reflective microwave switch. The switch is novel in that it utilizes direct optical control, whereby the optically controlled GaAs FET is directly in the path of the microwave signal and therefore relies on optically-induced variations in the microwave characteristics of the switch. This contrasts with previous forms of optically controlled switches which rely on indirect methods with the optical stimulus inducing variations in the DC characteristics of the GaAs FET, such that there is no direct interaction between the optically illuminated GaAs FET and the microwave signal. Measured and simulated results relating to the switching performance and transient response of the direct optically controlled microwave switch have been obtained and published as a result of this work. For the first time, good agreement is achieved between the measured and simulated results for the rise and fall times associated with the transient response of the gate photovoltaic effect in optically controlled GaAs FET switches. This confirms that the GaAs FET, when used as an optically controlled microwave switch, has a transient response of the order of several micro-seconds. An enhanced model of the GaAs FET switch has been developed, which represents a more versatile approach and leads to improved accuracy in predicting switching performance. This approach has been shown to be valid for both optical and electrical control of the GaAs FET. This approach can be used to model GaAs FET switches in discrete or packaged forms and predicts accurately the occurrence of resonances which may degrade the switch performance in both switching states. A novel method for tuning these resonances out of the switch operating band has been developed and published. This allows the switch to be configured to operate over the frequency range 1 to 20 GRz. The agreement between the models and measured data has been shown to hold for two very different GaAs FET structures. The results of the direct optically controlled microwave GaAs FET switch have been used as the basis for the design of a novel direct optically controlled microwave phase shifter circuit; Measured and simulated results are in good agreement and verify that the performance of the optically controlled phase shifter is comparable with previously published results for electrically controlled versions of the phase shifter. The 10 GRz phase shifter was optically controlled over a 1 GRz frequency range and exhibited a mid-band insertion loss of 0.15 dB. The outcome of the work provides the basis for directly controlling the phase of a microwave signal using the output of an optical sensor, with the GaAs FET acting as an optical-to-microwave transducer through a monolithic interface.

This thesis details the creation of a novel acoustic device, one which requires no power and is activated by the frequency of an acoustic wave. This device, named an acoustic switch in this paper, lays dormant until a continuous wave acoustic signal excites it at its specific design frequency, at which point it outputs a voltage. There currently are devices, namely hydrophones, that yield similar results, but are not activated by a specific frequency. The acoustic switch can be used in applications that require acoustic communications where power usage is critical, such as in battery powered unmanned underwater vehicles. The acoustic switch operates based on the principles of resonance induced by acoustic signals. Resonance creates large displacement harmonic motion in a mass spring system and this displacement can be converted to electrical signals. This thesis lays out the mechanical design of three different types of acoustic switches, each acting on different modes of resonance. The designs are analyzed numerically and through finite element analyses to determine the resonance frequency of each as a function of size, and the sensitivity of each design. A proof of concept prototype is constructed and successfully tested in the acoustic laboratory at Boston University to prove that an acoustic switch can work. The analyses show that designs can be created in the diameter range of 5 cm to 200 cm with actuation frequencies from 2,000 Hz to 50,000 Hz, where the size is inversely proportional to the actuation frequency. The designs can have sensitivities up to 15,000 Volts per Pascal of peak pressure amplitude. The voltage output from the switch can either be used as is or be fed to an ultra low power signal conditioning unit. The signal conditioning units use energy efficient active electronics and have a battery life of up to 46 years. The acoustic switch can usher in the development of a new category of low power sensors that can be used in commercial, military, and consumer applications.

abstract: A new type of Ethernet switch based on the PCI Express switching fabric is being presented. The switch leverages PCI Express peer-to-peer communication protocol to implement high performance Ethernet packet switching. The advantages and challenges of using the PCI Express as the switching fabric are addressed. The PCI Express is a high-speed short-distance communication protocol largely used in motherboard-level interconnects. The total bandwidth of a PCI Express 3.0 link can reach as high as 256 gigabit per second (Gb/s) per 16 lanes. Concerns for PCI Express such as buffer speed, address mapping, Quality of Service and power consumption need to be considered. An overview of the proposed Ethernet switch architecture is presented. The switch consists of a PCI Express switching fabric and multiple adaptor cards. The thesis reviews the peer-to-peer (P2P) communication protocol used in the switching fabric. The thesis also discusses the packet routing procedure in P2P protocol in detail. The Ethernet switch utilizes a portion of the Quality of Service provided with PCI Express to ensure guaranteed transmission. The thesis presents a method of adapting Ethernet packets over the PCI Express transaction layer packets. The adaptor card is divided into the following two parts: receive path and transmit path. The commercial off-the-shelf Media Access Control (MAC) core and PCI Express endpoint core are used in the adaptor. The output address lookup logic block is responsible for converting Ethernet MAC addresses to PCI Express port addresses. Different methods of providing Quality of Service in the adaptor card include classification, flow control, and error detection with the cooperation of the PCI Express switch are discussed. The adaptor logic is implemented in Verilog hardware description language. Functional simulation is conducted in ModelSim. The simulation results show that the Ethernet packets are able to be converted to the corresponding PCI Express transaction layer packets based on their destination MAC addresses. The transaction layer packets are then converted back to Ethernet packets. A functionally correct FPGA logic of the adaptor card is ready for implementation on real FPGA development board. / Dissertation/Thesis / M.S. Electrical Engineering 2012

The advance of internet applications, such as video streaming, big data and cloud computing, is reshaping the telecommunication and internet industries. Bandwidth demands in datacentres have been boosted by these emerging data-hungry internet applications. Regarding inter- and intra-datacentre communications, fine-grained data need to be exchanged across a large shared memory space. Large-scale high-speed optical switches tend to use a rearrangeably non-blocking architecture as this limits the number of switching elements required. However, this comes at the expense of requiring more sophisticated route selection within the switch and also some forms of time-slotted protocols. The looping algorithm is the classical routing algorithm to set up paths in rearrangeably non-blocking switches. It was born in the electronic switch era, where all links in the switches are equal. It is, therefore, not able to accommodate loss difference between optical paths due to the different length of waveguides and distinct numbers of crossings, and bends, leading to sub-optimal performance. We, therefore, propose an advanced path-selection algorithm based on the looping algorithm that minimises the path-dependent loss. It explores all possible set-ups for a given connection assignment and selects the optimal one. It guarantees that no individual path would have a sufficiently substantial loss, therefore, improve the overall performance of the switch. The performance of the proposed algorithm has been assessed by modelling switches using the VPI simulator. An 8×8 Clos-tree switch demonstrates a 2.7dB decrease in loss and 1.9dB improvement in IPDR with 1.5 dB penalty for the worst case. An 8×8 dilated Beneš shows more than 4 dB loss reduction for the lossiest path and 1.4 dB IPDR improvement for 1 dB power penalty. The improved algorithm can be run once for each switch design and store its output in a compact lookup table, enabling rapid switch reconfiguration. Microelectromechanical systems (MEMS) based optical switches have been fabricated with over 1,000 ports which meet the port count requirements in data centre networks. However, the reconfiguration speed of the MEMS switches is limited to the millisecond to microsecond timescale, which is not sufficient for packet switching in datacentres. Opto-electronic devices, such as Mach-Zehnder Interferometers (MZIs) and semiconductor optical amplifiers (SOAs) with nanosecond response time show the potential to fulfil the requirements of packet switching. However, the scalability of MZI switches is inherently limited by insertion loss and accumulated crosstalk, while the scalability of SOA switches is restricted by accumulated noise and distortion. We, therefore, have proposed a dilated Beneš hybrid MZI-SOA design, where MZIs are implemented as 1×2 or 2×1 low-loss switching elements, minimising crosstalk by using a single input, and where short SOAs are included as gain or absorption units, offering either loss compensation or crosstalk suppression though adding only minimal noise and distortion. A 4×4 device has been fabricated and exhibits a mere 1.3dB loss, an extinction ratio of 47dB, and more than 13dB IPDR for a 0.5dB power penalty. When operating with 10 Gb/s per port, 6pJ/bit energy consumption is demonstrated, delivering 20% reduced energy consumption compared with SOA-based switches. The tolerance of the current control accuracy of this switch is very broad. Within a 5 mA bias current range, the power penalty can be maintained below 0.2 dB for 8 dB IPDR and 12 mA for 10 dB IPDR with a penalty less 0.5 dB. The excellent crosstalk and power penalty performance demonstrated by this chip enable the scalability of this hybrid approach. The performance of 16×16 port dilated Beneš hybrid switch is experimentally assessed by cascading 4×4 switch chips, demonstrating an IPDR of 15 dB at a 1 dB penalty with a 0.6 dB power penalty floor. In terms of switches with port count larger than 16×16, the power penalty performance has been analysed with physical layer simulations fitted with state-of-the-art data. We assess the feasibility of three potential topologies, with different architectural optimisations: dilated Beneš, Beneš and Clos-Beneš. Quantitative analysis for switches with up to 2048 ports is presented, achieving a 1.15dB penalty for a BER of 10-3, compatible with soft-decision forward error correction.