The paper discusses a method for measuring the profile of the refractive index of an optical fiber and presents the results of a computational experiment that confirm the efficiency of the developed technique.
In this paper, we present the experimental impulse-radio transmission based on spectral modulation technique aimed at improving the energy efficiency, noise immunity and interception security of high-speed Radio-over-Fiber communication systems. The proposed modulation method is based on frequency-shift keying of three wideband solitonshape pulses with central frequency hopping in the desired frequency range. Mathematical and simulation models for the modulation and symbol coding techniques are provided. The system performance was evaluated through experimental BER measurement on the basis of the ultra-wideband laboratory test bench under the strict regulations of the SCRF spectral emission mask for ultra-wideband systems in Russia. A comparison of the obtained results with the current record of impulse-radio transmission under the SCRF spectral mask showed that the proposed spectral modulation method provides less achievable wireless transmission distance, however gaining into interception security of the link. Nevertheless, the employment of the improved decoding technique can fix this disadvantage. The achieved results demonstrate the application viability of the proposed method in high-speed Radio-over-Fiber communication systems.
KEYWORDS: Signal generators, Radio optics, Radio over Fiber, Antennas, Modulation, Telecommunications, Fiber optics, Orthogonal frequency division multiplexing, Prototyping, Channel projecting optics
This paper describes the operation of the prototype of the Radio-over-Fiber telecommunication system with the generation of OAM signals in the W-band. A method for generation both a radio and an optical OAM signal in RoF is proposed, a method for useful information transmission using OFDM technology in the considered system is described, an approach to converting optical vortexes into the radio domain is proposed, and a feedback channel simulation in RoF systems using OAM signals is carried out.
In this paper, an alternative fiber-optic method for forming vortex modes based on a chiral (twisted) microstructured fiber is proposed. This fiber can be considered as a ring-core fiber with ring core formed by capillaries. Besides, optical fibers design for transmitting optical vortexes over long distances. i.e. a vortex-maintaining fiber is also proposed. This fiber is a multimode fiber with an extremely large core. A comparison of the different types of vortex generation and vortex-maintaining fibers is also given. Both proposed fibers can be used in Radio over Fiber systems applying vortex beams.
KEYWORDS: Modulation, Orthogonal frequency division multiplexing, Radio over Fiber, Telecommunications, Signal to noise ratio, Mathematical modeling, Modulators, Fourier transforms, Fiber optics
In this paper we propose novel modulation technique based of quaternion signals aimed at incrising the capacity of Radio-over-fiber (RoF) systems based on OFDM technology. The application of hypercomplex quaternion signals processing has already demonstrated many advantages over the conventional analytical signals. The mathematical and simulation models of the quaternion QPSK modulator and demodulator are presented. Next, the improved scheme for OFDM RoF system is provided taking into account the quaternion signal processing. Simulation and evaluation of the proposed models were carried out by transmitting the QQPSK signal over the RoF system with AWGN wireless channel. The obtained BER vs SNR results for proposed modulation technique were compared to conventional QPSK providing double channel capacity with a little degradation of the noise immunity for QQPSK technique.
In this article the propagation of soliton-like vortexes in the optical segment of Radio-over-Fiber system is considered. The approach is based on solution of nonlinear Schrödinger equation (NSE) for Kerr-type nonlinear medium. A numerical NSE solution for vortex solitons was obtained; simulation of the soliton-like vortexes propagation over an optical fiber was performed. Moreover, a phase-amplitude filter forming optical signals with a set orbital angular momentum state and polarization conserving during propagation through an optical fiber was simulated. The calculation of amplitude-phase filter was conducted based on spinor representation of Maxwell’s equations.
KEYWORDS: Orthogonal frequency division multiplexing, Signal attenuation, Modulation, Radio over Fiber, Signal to noise ratio, Signal processing, Non-line-of-sight propagation, Telecommunications, Atmospheric propagation, Systems modeling
In this paper we present advanced modulation and coding techniques for telecommunication systems based on Orthogonal Frequency Division Multiplexing and Radio-over-fiber technologies operating in the subteraherz frequency range 75-110 GHz (W-band). The scheme for the Radio-over-fiber communication system based on full-optical frequency upconversion, and detailed description of the W-band wireless channel are presented. As a result, the main factors affecting the quality of the transmitted radio signal are identified, against which the developed modulation formats are aimed. Improving the efficiency of the Radio-over-fiber system is achieved in two stages: by reducing the interchannel interference due to the windowing of received signal, and reducing the peak-to-average power ratio by precoding the subcarrier frequencies of the group spectrum; by increasing the signal-to-noise ratio when using constellation rotation technique. Obtained simulation results showed that application of the proposed advanced modulation and precoding techniques in Radio-over-fiber systems provides the improvement of energy efficiency and noise immunity.
KEYWORDS: Radio over Fiber, Antennas, Telecommunications, Prototyping, Radio optics, Data transmission, Field programmable gate arrays, Signal generators, Phased arrays
The paper describes the results of experimental investigation of the bench, which represents UWB RoF communication system. This bench performs the first prototype of such system and allows it to study from different sides and on different scales. The whole scheme of the bench as well as the detailed description of its elements and characteristics are presented, also the specific issues regarding the connection of the elements are observed. The specific feature of this scheme is application of the phased antenna array as the radiating element of the radio part, which revealed the uncommon questions of matching RoF signal, being transformed from optical into radio domain. The experiment methods are explained in detail. The obtained results are presented and thoroughly analyzed, which revealed that the bench characteristics satisfy the thresholds, set before. Also the experiments on data transmission proved the possibility of successful high-speed data transmission in IR-UWB frequency range on the basis of Radio-over-Fiber technology.
KEYWORDS: Waveguides, Radio optics, Antennas, Control systems, Fiber optics, Refractive index, Distortion, Phased arrays, Radio over Fiber, Phase shifts
The task of the antenna array radiation pattern optical control for ultra-wideband radio emission is considered in the paper. A fiber-optic phasing scheme is proposed, which is part of a complex fiber-optic device. The control device layout and the radio-photon segment layout photos are presented. An analytical model of the optical phasing process is developed that provides the frequency bands number calculation. The number of bands, on which a wide frequency range should be divided, depends on the permissible level of the array radiation pattern distortion. The results of experimental approbation of the radio lobe phasing control in the frequency band of 200 MHz, divided into 3 subbands of 70 MHz, are presented.
This paper describes objectives on inner pipeline fault detection device modeling designated to monitor pipeline in real time. Due to high demands to high-speed and miniature measurements of such devices it is suggested to use implementations on the basis of fiber optic and radio-photonic mode of operation. A functional equipment design containing fiber optic generation and complex optic impulses transformation transmitted into radio trunk circuits are developed. Physical implementation of the suggested model is estimated as well as an analytical model for propagation of pilot signal on the basis of the Maxwell system of equations for partially conductive and simultaneously scattering medium.
KEYWORDS: Radio optics, Instrument modeling, Optical amplifiers, Switches, Switching, Photography, Radio over Fiber, Systems modeling, Telecommunications, Fiber optics
This article examines the devices for optical signal splitting and chirping device modeling. Models with splitting and switching functions are taken into consideration. The described device for optical signal splitting and chirping represents interferential splitter with profiled mixer which provides allocation of correspondent spectral component from ultra wide band frequency diapason, and signal phase shift for aerial array (AA) directive diagram control. This paper proposes modeling for two types of devices for optical signal splitting and chirping: the interference-type optical signal splitting and chirping device and the long-distance-type optical signal splitting and chirping device.
KEYWORDS: Control systems, Fiber optics, Refractive index, Radio optics, Signal attenuation, Antennas, Ultraviolet radiation, Radio over Fiber, Channel projecting optics, Telecommunications
This paper describes functional principles of a device for optical signal splitting and chirping. The offered device is to fulfill functions of such optical signal distortions compensation within FOCL RoF as linear attenuation (LA) and chromatic dispersion (CD); and it should also split optical signals for its feeding to radio emitting components, compounding aerial array (AA), and control radio emitting antenna lobe. In the meantime the device for optical signal splitting and chirping can inject losses into transferred signal, though they should be within tolerant values for conventional FOCL components.
KEYWORDS: Data transmission, Pulse shaping, Gaussian pulse, Radio over Fiber, Telecommunications, Transmitters, Antennas, Signal to noise ratio, Digital signal processing, Receivers
Experimental bench, which provides high-speed data transmission for IR-UWB Radio-over-Fiber systems on the basis of Gaussian pulses, is presented in the paper. Experiment setup and results are described and discussed.
KEYWORDS: Signal generators, Prototyping, Antennas, Telecommunications, Radio over Fiber, Modulators, Microwave radiation, Signal to noise ratio, Fractal analysis, Radio optics
Wireless part of the laboratory bench, implementing IR-UWB Radio-over-Fiber system, is described in the paper. Experimental prototype of fractal antenna radiating system (FARS) is considered, various transmission modes of the laboratory bench, which allow to investigate technical specifications, are described. Research results are presented and analyzed.
The paper describes the application of IR-UWB technology for organizing the radio part of Radio-over-Fiber system. Four physical layer components are proposed and designed in the paper: three microstrip filters and UWB antenna. Firstly the effective SCRF mask was calculated to ensure electromagnetic compatibility with existing radio services. Then this mask was considered as a cost function for filters design. The simulation was made with Agilent Genesys™ and CST Microwave Studio. All the devices have shown good performance and could be implemented on one circuit board for reducing losses.
KEYWORDS: Modulators, Signal generators, Radio over Fiber, Photodiodes, Continuous wave operation, Modulation, Signal detection, Eye, Terahertz radiation, Optical amplifiers
Ultra-wideband (UWB) signal generation approach for Radio-over-Fiber (RoF) systems is proposed in the paper. Impulse-radio ultra-wideband (IR-UWB) transmission technology experimental realization comply with State Committee on Radio Frequency (SCRF) regulations is offered in the paper. Three separate IR-UWB signals with carrier frequencies 4,5 GHz, 7 GHz and 9,5 GHz are generated. Such frequencies were chosen because of SCRF spectral mask "windows". The frequencies 4,5 GHz, 7 GHz and 9,5 GHz are the central frequencies of these "windows". To assess the performance of proposed system bit error rate (BER) measurements were taken.
UWB signal generation schemes and received IR-UWB signal are shown in the figures. The correlation between BER and received optical power is given in the paper. In the case of UWB signal photonic generation approach the correlation between BER and received optical power for different SMF fiber lengths is given.
Clear nanocrystalline material receipt possibilities are described in the paper. We investigated the possibility to process the glass-ceramics and quartz by intense torsion under high pressure. We found that due to the lack of plasticity of the material zone to maintain the integrity of the sample it is necessary to apply heating up to 200-250°C. The resulting material is supposed to be used in fiber-optic telecommunication systems. We conducted mathematical modeling of the refractive index in the linear and nonlinear mode capacities for nanostructured glass-ceramics. The analytical method is based on the strain oscillator motion under outer light wave effect model. We also found the coefficient of nonlinear stiffness for nanostructured glass-ceramics.
The device for positive chirping of a signal in a fiber optical line is offered. The device is based on two Fabry–Perot resonator with additional fiber optical cannels. If to execute the amalgamator from an erbium doped material, the device will supply amplification of a target signal, which is important for distribution access systems (for example, Radio-over- Fiber systems (RoF)). The device provides selectivity for spectral components of entrance radiation, that allows to operate of chirp. Built-in the converter of length provides in additional fiber optical cannels tuning the chirp under the given size.
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