Tamas Cseh

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A low cost radio over fiber (RoF) systems using vertical cavity surface emitting lasers (VCSEL) and multimode fiber (MMF) were studied. The system concept was designed and investigated by simulation. The electrical circuits were designed and fabricated. The simulation results were verified by measurement. The result of the simulations and measurements of(More)
Multimode fiber links can offer a useful approach for low cost and short Radio over Fiber (RoF) systems. However, in these connections the distortion effects are higher than in a singlemode fiber system. These effects can be compensated by a suitable optical receiver. In this paper an improved receiver structure is investigated for Radio over Multimode(More)
VCSELs (Vertical-cavity surface-emitting lasers) offer a number of unique advantages: a threshold current that is low and stable with temperature so that electricity is converted to light with a very high efficiency; the ability to be modulated at very high frequencies; a circular output beam with low divergence, simplifying the optical system. Lifetime(More)
In this paper, we propose a hybrid radio over multi-mode/single-mode fibre and free space optics (RoMMF/SMF-FSO) system to enhance the 4<sup>th</sup> generation-long term evolution (4G-LTE) signal performance when used in local area access networks. A single mode fibre pigtailed gradient index lens is used to minimise the modal effect of the optical link at(More)
In this paper, the combination of radio over multimode fibre and radio over free space optical systems are experimentally investigated. A mode filtering technique is adopted in order to deal with the modal effects in such hybrid systems. Considering mode filtering effect, we have determined transfer function and performed link budget analysis. Measurement(More)
In this paper, we propose a new scheme for the integration between the outdoor and indoor 4G long term evolution networks employing the radio-over free space optics technology for the rural environments applications to reduce the deployment cost. We experimentally characterise the system performance under the atmospheric fading effects including thick fog(More)
In this paper two millimetre-wave (mm-wave) generation techniques involving optical heterodyne detection and the Mach-Zehnder Modulator (MZM) based optical comb technique are investigated. The heterodyne detection system is followed by a second order electrical feedback loop to reduce the phase noise. Simulations are carried out to study the effects of the(More)
Multimode fibers (MMFs) can be a cost effective solution for Radio over Fiber links. Compared to single mode fibers (SMF) the larger core of the MMF reduces the installation cost, however, MMFs have higher linear distortion effect. The impact of the modal dispersion limits the quality of communications. By applying mode filters, the effect of the modal(More)
Multimode fiber (MMF) links are currently attracting much interest as a medium for the transmission of radio signals over optical links called Radio over Fiber (RoF) link. However, the application is restricted, because the capacity of MMF transmission is limited by intermodal dispersion which is caused by the different propagation speeds of the fiber(More)