Analyzing data transmission parsimeters with optical fiber based on Asho Begune modulation

Dissertation for Master's Degree in Electrical Engineering, Electronics Orientation

Abstract

Chaos theory was founded by Lorentz at the end of the 20th century. Chaos science investigates non-linear systems and their behavior in different conditions. Since the systems around us are mostly non-linear, by creating feedback in them, they may show chaotic behavior, so chaos theory can be used to build chaotic systems and signals.  . One of the standard chaotic wave generating systems is the Chua Oscillator, which is examined in full detail to learn about the chaotic system's performance. Since chaotic signals have unique properties such as high bandwidth, proper correlation properties, pseudo-noise and sensitivity to the initial value, and at the same time, they are very suitable for telecommunication systems. In addition, due to the importance of optical communication and the large volume of information transmission in this sector, attention has been increased day by day, and for this reason, efforts to increase the transmission capacity and its security are also of great importance. Therefore, in this thesis, an optical communication system based on coherent chaotic modulation has been prepared. Chaotic modulation has been used as an external intensity (amplitude) modulation for the optical system. Therefore, in general, the application of chaos theory has been used in chaotic modulations for the optical telecommunication system so that the properties of chaotic systems can be used for optical telecommunication.  Therefore, the valuable goal of the thesis is to investigate the effects of chaotic modulation in the optical fiber environment, and for this reason, first chaotic modulations and then optical fiber were designed. CSK, DCSK, ACSK, FM-DCSK modulations are mentioned among the digital chaotic modulations. In this thesis, ACSK non-polar chaotic modulation is used to evaluate the chaotic properties of the optical transmission medium. In addition to digital chaotic modulation, analog chaotic modulation has also been avoided, and the difference in the results of these two modulations is noticeable in the chaotic transmission section. The structure of optical communication has also been simulated with the help of SoftTDM toolbox of Matlab software.

Key words: chaos theory - chaotic signals - secure communication - optical communication

Chapter 1: Basics and generalities of chaos theory research

Abstract

In the definition of the problem, it can be said that chaos is one of the new sciences that has been able to enter all scientific fields in recent years under the name of chaos theory. One of these fields is to enter the engineering fields, so in this research, this theory (chaos) in electronics will be examined first. For this purpose, in this chapter, the basics and history of chaos theory will be explained and the reasons for the discovery of this theory in electronics will be discussed. And we will learn about the main cause of chaotic behavior.

Introduction

Determinism and determinism is a philosophical belief according to which every event or action is considered the inevitable result of previous events and actions. Therefore, according to this belief, any event or action can be predicted before its occurrence, or the reasons for the occurrence of that action can be found out in retrospect. They imagined the world in a set of systems that move in a specific and predictable way according to the algebraic laws of nature. Therefore, they believed that the effects are linear, for them, specific causes. The person who strengthened the base of determinism in modern science was an English scientist named Isaac Newton who lived in England about three hundred years ago. Newton's laws are completely based on certainty, because they claim that everything that happens in the future is completely determined by what happened in the past.

One of the fundamental principles of experimental science is that measurements do not have infinite accuracy in practice, but there is a degree of uncertainty in measurements. In fact, to measure and record each measurement, an infinite number of digits are needed to reduce the uncertainty as much as possible, but this can never completely eliminate the uncertainty. In the science of dynamics, the presence of uncertainty in any real measurement means that in the study of any system, its initial conditions cannot have infinite accuracy, and this problem sooner or later leads to uncertainty in the future behavior and predicting how the system will function. More than a century ago, based on the second principle of thermodynamics, Mr.

More than a century ago, based on the second principle of thermodynamics, Mr. Ludig Boltzmann proposed the hypothesis of initial turbulence in the study of the irregular behavior of gases, so that entropy became a topic of discussion. All these topics were raised with reference to the same inaccuracy in measurement. This scientific view and philosophical discussions in the field of science, about the uncertainty in measurements and the problem of disorder, all before the work (proposition of chaos theory) of Edward Lorentz, one of the mathematicians of MET University in America, who was very interested in weather research and its forecasting. With the discovery of the butterfly effect phenomenon and the sensitivity of many systems to the initial condition and as a result of the inherent nature of chaotic behavior in many systems based on nonlinear dynamic dynamics, the scientific and philosophical view of Heisenbergian uncertainty led to the inherent uncertainty in nonlinear dynamic dynamics and as a result creating behavior with seemingly irregular manifestations, namely chaotic dynamics. From this time on, the concept of chaos had not only taken a theoretical and mental form. But also as a phenomenon that can be modeled and simulated, it was discussed and researched in scientific circles[1].

Concepts and History of Chaos

Chaos [1] (pronounced in English as Kias) literally means chaos and disorder. The root of chaos comes from the Roman word Chaos, whose concept belongs to the ancient Roman poet named Ovid - in his opinion, Chaos was disorder and formless matter that had unlimited space and dimensions, so that it is assumed that it existed before the orderly world was formed, and the creator of existence created the orderly world from it. Chaos is a term that describes seemingly complex behavior in seemingly well-behaved and simple systems that can be seen in many real-world phenomena. Chaotic behavior, at first glance, seems disorderly and random, like the behavior of a complex system with very high degrees of freedom or like the behavior of a system that is affected by external noise.

The phenomenon of chaos was first observed during meteorological studies by a person named Edward Lorentz through numerical calculations and computer simulation. In 1961, as a meteorologist at MIT University, he was working on atmospheric modeling using computers. By choosing a simplified model of the Raleigh-Bernard phenomenon, which occurs in a layer of air caused by a temperature difference, he proposed that the response and behavior of this phenomenon can be obtained by a system of three nonlinear differential equations. He then drew a diagram of wind direction and speed with the help of a primitive calculator, thus achieving a great discovery. He found that the slightest change in the initial conditions caused a change in behavior patterns. In such a way, the answer is completely different, and based on this, the issue of "butterfly effect" was raised and the unpredictability of the weather situation for a long time was confirmed. Lorentz's findings were so fundamental that it started a wave to expand the research on the nature of chaos. In this way, a group of scientists, instead of relating the changes in the behavioral patterns of the system due to a small change in the initial conditions, to the issue of disturbance and noise from the environment on the system, to the nature of the behavior They knew the dynamic dynamics of nonlinear and within the related system. As a result, the phenomenon of chaos was considered as an inherent property and special behavior of nonlinear systems.

In the figure below, the chaotic third order dynamics that Lorentz used can be seen. You can see an example of the chaotic behavior of this dynamic in figure (1-2)[2].

Figure 1-1. An example of an experiment that leads to Lawrence's differential equations is x_1 (indicated by x in the equations in the text) average fluid rotation speed, x_2 (indicated by) horizontal temperature difference distance and x_3 (indicated by z) vertical temperature difference[2].

Figure 1-2. Chaotic behavior of Lorenz dynamics[2]

1-4- The first recognition of chaos in electronics using a simple electric circuit

We have chosen such a simple electric circuit to show that first, chaotic behavior can often exist in real systems, secondly, chaotic behavior can exist and be observed in very simple systems and everyday systems that are many around us. All the parts that exist in this electrical circuit are found in radios, televisions, tape recorders, and most electrical devices. This electric circuit shown in Figure (1-3), as you can see, this very simple circuit only consists of a diode, inductor and an AC voltage source (V(t)=Vo sin(2) and a DC voltage source