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The wavelength division multiplexing (WDM) type optical communication significantly increases the transmission capacity. However, one of the key issues is how we can reduce the pulse broadening and the interaction between the neighboring channels due to the nonlinear effects. The optical soliton offers the answer to this question. The soliton pulse can keep its shape during propagation, when there...
The single drive Mach-Zehnder interferometer modulator is used basically for optical intensity modulation. It is well known that its modulation characteristic exhibits a significant nonlinearity at increased drive level. However, we draw the attention to the problem that the intensity modulation is associated with a parasitic phase modulation. In this paper we investigate the source of parasitic phase...
In the 5G mobile networks, the optical signal transmission will be widely used. Two main applications are important: short links for the access networks and long links in the backbone of the system. In this paper we investigate both applications. For that purpose we developed a method using simulations. Based on our simulation results we present proper methods to avoid distortion, which is caused...
Several system applications require optical transmission of very high bit-rate digital as well as microwave and millimeter-wave carrier signals. Without completeness, a few recent applications are mentioned such as: 5G and Radio-over-Fiber (RoF) systems, Gigabit Passive Optical Networks (GPON), optical interconnection within Cloud for telecommunication Network Elements (NE), upgrade of mobile access,...
In this paper, we focus on the study of large bandwidth wireless signal transmission following a 60 GHz standard over a multimode fiber link used to cover optical distribution for the last mile. To reduce the multimode effects within the fiber, a single mode fiber is first added to play a role of mode filter, and then replaced by a Mandrel as a filter. Error vector magnitude (EVM) is used as a metrics...
This paper proposes an optimum hybrid radio over multi-mode fiber and free space optics (RoMMF-FSO) system to enhance the last mile bottleneck issues of wireless communication systems. Single mode fiber (SMF) and gradient index (GRIN) lenses are used as mode filtering techniques to optimize the system performance by mitigating the modal effects produced by multimode optical fiber networks. We characterize...
The aim of the paper is to present a new integrated microstrip diplexer applicable in radio over fiber (RoF) links. That integrated microstrip diplexer has a much simpler construction with better characteristics compared to the widely used ones. The attenuation of the diplexer is significantly reduced by integrating the divider with the filters without using isolators between them. Two diplexer samples...
This paper shows the design and implementation of an UWB transmitter and a receiver built with discrete parts. The transmitter is based on a step recovery diode and the receiver is built around an ultra-high speed comparator. The circuits are designed in a manner, that all components are low cost discrete elements and both the transmitter and the receiver can be easily interfaced to low speed and...
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 and a moderate turbulence regime considering...
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 of the error vector magnitude (EVM) was accomplished...
In this paper the investigations of the parasitics in a fabricated X-band tuneable metamaterial isolator are presented. The isolator applies a microstrip left handed artificial transmission line (LHTL) with Butterworth phase response on an anisotropic ferrite substrate material. The structure is simplified and optimized to reduce the harmful right handed and coupled parasitic effects to achieve stable,...
In this paper, the effects of special harmonic loads are presented in the case of microwave amplifiers. The third-order intercept point (IP3) and the 1-dB compression point (P1dB) of the amplifier are improved with the use of special harmonic loads. To demonstrate this effect an amplifier was designed applying a BFG424F NPN type bipolar transistor. The amplifier was designed for a broad band providing...
Creating a radio frequency (RF) signal from the optical domain is a widely used technique for THz signal generation. The RF signal is obtained applying two optical carrier signals by photomixing in a photodiode. Because of the quadratic characteristic of the photodiode the frequency difference of the two lasers will appear in the electrical spectrum. There are two kinds of optical sources for photomixing...
More than fifty years ago I was involved into research and development of microwave circuits based on the waveguide technology. At the beginning of my work I had the opportunity to be visiting researcher at the Polytechnic Institute of Brooklyn. During my stay there I heard about the book entitled: “Microwave filters, impedance-matching networks, and coupling structures”. I felt that was the book...
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 dispersion is reduced, and better performance...
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 fiber systems. N-QAM radio signal transmission...
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 modes. The free space propagation of radio waves...
The OFDM modulation format is widely used in several wireless applications because it is robust against multi-path distortions in the radio channel. The OFDM signals are usually transmitted over an optical link to the wireless network. However OFDM is sensitive to the channel nonlinearities. The nonlinearity of this type of modulation can cause distortion and this way limitation on the optical transmission...
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 parameters are not degraded when overdriving...
For interconnections between the stations of mobile networks optical links are frequently used. The mobile networks require new modulation methods to achieve higher transmission capacity. For that purpose the m-QAM modulation method is a proper approach. On the other hand, the signal transmission in the mobile network is strongly affected by multipath wave propagation. The OFDM modulation can counterbalance...
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