Due to ever-faster processor clock speeds, there is a rising need for increased bandwidth to transfer large amounts of data, noise-free, within computer and telecommunications systems. A related requirement is the demand for high bit-rate, short-haul links. Here, optical transmission paths are a viable alternative to high-frequency electrical interconnections, whereby layers with integrated waveguides are particularly suitable. The reasons for this include that a higher connection density can be achieved and the power dissipation, as well as interference from electromagnetic radiation, are significantly lower. The article presents general considerations and the results of research conducted by the German BMBF Project NeGIT, into the manufacture of circuit boards with embedded polymer optical waveguides. The electrical-optical boards were fabricated using precise photolithographic processes and standard lamination methods. They possess the thermal stability necessary for manufacturing processes and operational conditions, in terms of both bond strength and the stability of the optical properties. As part of this project, a design of an optical coupling in the daughter card and board backplane interfaces was developed and is presented as the centerpiece of this study.
As a part of the EU-FP7 R&D programme, the OMEGA project (hOME Gigabit Access) aims at bridging the gap between mobile broadband terminals and the wired backbone network in homes. To provide Gb/s connectivity a combination of various technologies is considered. Beside radio frequencies, the wireless links will use infrared and visible light. Combined with power-line communications this enables a home area network (HAN) that meets the vision of broadband home networking dasiawithout new wirespsila. A technology-independent MAC layer is foreseen to control such network and to provide services as well as connectivity to any device the user wishes to connect. Moreover, this MAC layer should allow the service to follow the user from device to device in any room of a building /apartment. The contribution presents ideas and approaches for broadband optical wireless (OW) communications using infrared Gb/s hotspots and 100 Mb/s information broadcasting by means of interior lighting based on white-light LEDs. Important issues concerning the physical layer are discussed
In the present study turbulence characteristics from Reynolds Averaged Navier-Stokes simulations are used as input for the analytical prediction of fan broadband noise due to the interaction of the fan rotor wake turbulence with the outlet guide vanes. The aerodynamic excitation is modeled with a von Kármán spectrum and the blade response with the Sears function extended with a term considering the non-compactness of the source. The influence of different turbulence models, from state-of-the-art two-equation models to a Reynoldsstress transport model, on the simulated turbulence characteristics and consequently on the broadband noise prediction is investigated. Furthermore the impact of the two-equation model extensions for the effects of rotation, transition and the stagnation point is analyzed and discussed. The predicted noise spectra are compared to the experimental test data of the NASA Source Diagnostic Test fan rig. It has been found that different turbulence models and extensions can lead to a variation of predicted broadband interaction noise of up to 2 dB.
Future Home Access Networks (HANs) should operate at Gbit/s and provide data services that are as straightforward to use as an electrical outlet or any other utility. This is an extremely challenging goal, and an EU funded project 'Home Gigabit Access Networks' (OMEGA) aims to achieve this. In this project a significant part is to realize bi-directional Gigabit infrared (IR) optical wireless communications. In this paper we introduce the overall approach to the HAN, and outline the challenges and approaches required to implement these IR Gigabit links. Results from a proof-of-concept 1.25Gbit/s light-ofsight (LOS) IR link are shown, as well as designs for the first IR link demonstration.
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