1,723,466 research outputs found
Trends in electro-optical communication systems
Full text linkThis paper gives an overview of present status and future trends in Electro-optical communication
systems and networks. Within the architecture of Electro-optical communication networks, three
areas with a different type of research focus can be distinguished: the long haul links, the crossconnects and the access networks to the subscribers
Author Correction: Reconfigurable beam system for non-line-of-sight free-space optical communication
Full text linkAddendum: We were recently made aware of the fact that Professor Nabeel A. Riza’s laboratory theoretically proposed earlier a Non-Line of Sight (NLOS) indoor optical wireless communications arrangement with threedimensional optical beamforming via a spatial light modulator using diffuse reflections from diffuse optical elements1. This is exactly the type of arrangement that would benefit greatly from our technique, since the coherent arrayed optical transmitter (CAO-Tx) we proposed makes the reflection focus onto the receiver, rather than diffusely scatter it in all directions. We apologize for the omission of this prior-art
25.8 Gb/s Submillimeter Optical Data Link Module for Smart Catheters
Full text linkThe digitization of smart catheters will dramatically increase the demand for reliable and high data transmission in the distal tips. Optical fiber is a good candidate to provide high-speed data transmission. However, the extremely small size of the smart catheter tip, with less than a few millimeters in diameter, hampers the integration of optical fiber connections in the catheter tip. Our work presents a stand-alone optical data link module (ODLM) with a dimension of 240 μm × 280 μm × 420 μm for use in a 1 mm diameter intravascular ultrasound (IVUS) smart catheter. The fabrication of the ODLM is based on the Flex-to-Rigid (F2R) integration technology. In the ODLM, the flexible interconnects reroute the electrical contacts of the flip-chipped vertical-cavity sur-face-emitting laser (VCSEL) to the side of the device. This design enables the ODLM to be mounted on a flex-PCB and fit into a 200-300 μm gap in the IVUS catheter tip. An optical fiber that runs parallel to the catheter shaft is self-aligned to a commercially available VCSEL by inserting it into the through-silicon hole (TSH) of the ODLM. Clear eye diagrams prove the stand-alone ODLM can transmit 25.8 Gb/s, 231-1 Pseudo-Random Binary Sequence (PRBS) when driven through a high-speed bias-tee. The BER test indicates that error-free operation can be achieved at an optical output of around -4 dBm.Electronic Components, Technology and Material
Optimal controlled ALOHA for two-way data communication in a cable television network
Full text linkBased on a unified analysis of both pure and slotted ALOHA systems, a new control algorithm for ALOHA systems is proposed. A feature of great practical importance is the algorithm's automatic adjustment to changes in average traffic intensity or the (finite or infinite) number of active stations in the system. In addition, the algorithm has a low-complexity implementation. Computer simulations, concentrating on the use for two-way data communication in a cable television network, have demonstrated that the practical performance of the algorithm closely approximates the theoretical optimum, even under extremely heavy traffic load conditions. Furthermore, dynamic performance simulations have shown that the algorithm assures swift recovery from overload situation
Light transmission through a subwavelength slit: Waveguiding and optical vortices
No full textThe anomalous (i.e., more than 100%) light transmission through a subwavelength slit in a thin metal plate is accompanied by a combination of waveguiding and phase singularities of the field of power flow near the slit. The crucial role of these phase singularities (such as optical vortices and saddle points) in exciting the waveguide modes is systematically studied. We predict transmission efficiencies as high as 300% for certain configurations
Plasmon-assisted two-slit transmission: Young's experiment revisited
Full text linkWe present an experimental and theoretical study of the optical transmission of a thin metal screen perforated by two subwavelength slits, separated by many optical wavelengths. The total intensity of the far-field double-slit pattern is shown to be reduced or enhanced as a function of the wavelength of the incident light beam. This modulation is attributed to an interference phenomenon at each of the slits, instead of at the detector. The interference arises as a consequence of the excitation of surface plasmons propagating from one slit to the other. © 2005 The American Physical Society
An Integrated Simulation Environment for Testing V2X Protocols and Applications
Full text linkAbstractImplementation of Vehicle-to-everything (V2X) communication technologies, for traffic management, has been envisioned to have a plethora of far-reaching and useful consequences. However, before any hardware/software infrastructure can be developed and implemented, a thorough phase of testing is warranted. Since actual vehicles and traffic conditions cannot be physically re-constructed, it is imperative that accurate simulation tools exist in order to model pragmatic traffic scenarios and communication amongst the participating vehicles. In order to realize this need of simulating V2X technology, we have created an integrated simulation environment that combines three software packages, VISSIM (traffic modelling), MATLAB (traffic management applications) and NS3 (communication network simulation). The combination of the simulators, has been carried out in a manner that allows on-line exchange of data amongst them. This enables one to visualize whether a traffic management algorithm creates the desired effect and also the efficacy of the communication protocol used. In order to test the simulator, we have modelled the Green Light Optimized Speed Advisory (GLOSA) application, whose objective is communication of the present traffic signal phase information to oncoming vehicles using a transmitting unit installed on the signal itself. This information will allow the vehicles to calculate the desired speeds necessary to cross the relevant intersection without stopping. Therefore, a “Green Wave” can be created for all vehicles without the need to coordinate traffic signal timers, which can be rather complex in a multiple intersection traffic corridor
High capacity interconnection networks
No full textOptical interconnects are being considered for short link data networks as a solution enabling higher aggregate bit rates and lower power consumption. For short link length interconnects, as used in chip to chip interconnects, internal system backplanes and inter-system interconnects such as blade server backplanes, storage area networks and processing clusters, requirements are quite different to those for long distance telecommunications systems. Low power consumption, latency, and size become important criteria in addition to ultra high bandwidth. In order to achieve the projected ultra high capacity and low latency needs, we are considering optical switching fabrics. The optical switch, however, brings significant changes to the interconnect architecture in terms of how routing decisions are made and how contention resolution is managed. We discuss these issues and present our results for a multiwavelength optically switched interconnect
Predictive power control in wireless sensor networks
No full textCommunications in Wireless Sensor Networks (WSNs) are affected by dynamic environments, variable signal fluctuations and interference. Thus, prompt actions are necessary to achieve dependable communications and meet quality of service requirements. To this end, the reactive algorithms used in literature and standards, both centralized and distributed ones, are too slow and prone to cascading failures, instability and sub-optimality. We explore the predictive power of machine learning to better exploit the local information available in the WSN nodes and make sense of global trends. We aim at predicting the configuration values that lead to network stability. In this work, we adopt the Q-learning algorithm to train WSNs to proactively start adapting in face of changing network conditions, acting on the available transmission power levels. Our aim is to prove that smart nodes lead to better network performance with the aid of simple machine learning
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