With growing demands of Internet Protocol services for transmission capacity and speed, the solution for future highspeed optical networks is Optical Burst Switching that is a technology for transmitting large amounts of data bursts through a transparent optical switching network. To successfully transmit bursts over OBS network and reach the destination node, resource reservation schemes have to be implemented to allocate resources at each node. The OBS network model with one-way resource reservation schemes performed using OMNeT++ simulation environment is presented.
In today's overwhelming world of data, ultra-wideband communication systems are the inevitable parts of the communication society that has faced scientists with challenging and new problems. Appearance of nonlinear effects in optical fiber communication systems due to wideband data transmissions with the aid of ultra-short pulses has recently attracted a lot of publicity. In this paper a finite-difference method is used to solving the nonlinear Schrödinger equation. A not frequently used numerical method is developed by replacing the time end space derivates by central-difference replacements. Results from solving the nonlinear Schrödinger equation by using the numerical method called method of lines is used to simulate the propagation of Gaussian pulses in optical fibers. Gaussian input pulse was used for the analysis of dispersion effects. For the simulation was chosen the nonlinear Schrödinger equation modified for dispersion mode. Based on the changes of the chirp parameter have been achieved final shapes of transmitted Gaussian pulses. The main objective was to demonstrate the impact of the broadening factor of the pulse and to clarify the correlation between the change in phase and frequency chirp. The main goal of this paper is to describe and simulate effects of dispersion and nonlinear effects by using short Gaussian and super-Gaussian optical pulses. The effect of dispersion caused frequency shift which can be compensated by effect of self-phase modulation. Due to this numerical simulation we can identified the channel properties and also the control the domination of effects. This option can be very interesting in nowadays high-speed optical communication system.
With growing demands of Internet Protocol services for transmission capacity and speed, the Optical Burst Switching
presents the solution for future high-speed optical networks. Optical Burst Switching is a technology for transmitting
large amounts of data bursts through a transparent optical switching network. To successfully transmit bursts over OBS
network and reach the destination node, resource reservation schemes have to be implemented to allocate resources and
configure optical switches for that burst at each node. The one-way resource reservation schemes and the performance
evaluation of reservation schemes are presented. The OBS network model is performed using OMNeT++ simulation
environment. During the reservation of network resources, the optical cross-connect based on semiconductor optical
amplifier is used as the core node. Optical switches based on semiconductor optical amplifiers are a promising
technology for high-speed optical communication networks.
Although Fiber Bragg gratings (FBGs) are well known devices, their using as all-optical switching elements has been
still examined. Current research is focused on optimization of their properties for their using in future all-optical
networks. The main problem are high switching intensities needed for achieving the changes of the transmission state.
Over several years switching intensities have been reduced from hundreds of GW/cm2 to tens of MW/cm2 by selecting
appropriate gratings and signal parameters or using suitable materials. Two principal nonlinear effects with similar
power requirements can result in the bistable transmission/reflection of an input optical pulse. In the self-phase
modulation (SPM) regime switching is achieved by the intense probe pulse itself. Using cross-phase modulation (XPM)
a strong pump alters the FBG refractive index experienced by a weak probe pulse. As a result of this the detuning of the
probe pulse from the center of the photonic band gap occurs. Using of XPM the effect of modulation instability is
reduced. Modulation instability which is the main SPM degradation mechanism. We focused on nonlinear FBGs based
on chalcogenide glasses which are very often used in various applications. Thanks to high nonlinear parameters
chalcogenide glasses are suitable candidates for reducing switching intensities of nonlinear FBGs.
The word soliton refers to a special kind of wave packets that can propagate undistorted over long distances. As a source for generating soliton pulses in 1990 erbium doped lasers were used. Soliton transmission systems have been the subject of interest for years. It is known that interaction and the balance between the dispersion and nonlinear effects in optical fibers can lead to a special pulse behavior. Soliton pulses can propagate without any changes of the amplitude and the shape via long transmission systems. Due to this advantage they are of interest in long haul communication systems. Here we describe how the random change of input pulse chirp in optical fibers can affect the soliton propagation and interaction between two or more solitons. We have focused on describing some numerical approaches to solve the coupled nonlinear Schrödinger equations, which are useful by solving this kind of problem. Most of laser sources can be approximated by Gaussian distribution or in special cases the second hyperbolic pulses are generated to produce a soliton shaped pulse. The effect of pulse chirp can generate new frequencies due to the frequency chirp. In high bitratetransmission systems this chirp is very important to reduce, because of this new frequency can influence the neighbor channels and lead to BER increasing.
Although nonlinear fiber Bragg gratings (FBGs) are well known devices more than three decades their using as all-optical switching elements is still investigated. Current research is focused on optimization their properties for their using in future all-optical networks. The main problem is minimizing of switching intensities needed for achieving the changes of transmission state. Switching intensities were over several years reduced from hundreds of GW/cm2 to tens of MW/cm2. Reduction of switching intensities can be achieved by selecting appropriate gratings and signal parameters or using suitable materials. This contribution is focused on nonlinear FBGs based on chalcogenide glasses which are very often used in various applications. Chalcogenide glasses thanks to their high nonlinear parameters are suitable candidates for reducing switching intensities of nonlinear FBGs.
The propagation of optical pulses in dispersive nonlinear fibers is studied by using an adaptive split step Fourier method. Propagation of optical pulse is described by a generalized nonlinear Schrödinger equation. Various initial pulse shapes can be used, impact of group velocity dispersion up to the fourth-order dispersion, self phase modulation and their interplay are studied in connection with the dispersion and nonlinear length parameters. Properties of propagating field are analyzed in time and in frequency domain. For pulse propagation in telecommunication applications the results of implemented solutions are in good agreement with experiments.
Current optical communication systems have been usually deployed in different physical environments. All environmental conditions have different physical characteristics that can significantly influence transmission properties of these systems. In this article, we focus on possible temperature effects on the refractive indices of optical fibers and their transmission characteristics. The article also attempts to determine the impact of thermal effects caused by the propagation of optical radiation through optical fiber. We discuss the impact of the stochastic changes in susceptibilities and consequently nonlinear effects occurring in optical fibers and influencing the propagation of optical pulses. As input pulses the Gaussian pulses of intensities exceeding intensities of atomic electric fields in the fibers have been taken into account. For such pulses the refractive index changes can become nonlinear, especially in case when considerable environmental changes of temperature can occur. The numerical studies of the pulse propagations in such nonlinear environmental conditions have been performed in this article. Stochastic changes in temperature lead to changes in the phase shift which can influence the spreading of the pulse spectrum due to SPM. The aim is to simulate the final effect at pulse shape and spectrum of propagated Gaussian pulses.
Today's requirement for the transfer of information requires the use of broadband transmission systems. This need
has successfully addressed the use of WDM systems, where the transmission of multiple channels should address the
impacts of dispersion and nonlinear phenomena that occur during transmission. To describe these effects is useful to
solve the nonlinear Schrödinger equation (NLSE), which is a second order partial differential equation. It’s hard to be
solved by analytical methods. This paper deals with using one method of the group of finite-difference methods, the socalled method of lines to solve NLSE. The first part is focused on the propagation of the unchirped Gaussian pulse in optical fiber including group velocity dispersion and then we investigated the effect of GVD in the spread of two
Gaussian pulses in the same optical fiber. The results show the interaction of these pulses. Then we have focused on the behavior of different chirped Gaussian pulses propagating in optical fiber in anomalous dispersion regime.
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