Spectrum Of Erbium Doped Fiber Amplifier Computer Science Essay Example

windows wavelength of input signal, input powers and the pump power. But the length of the fiber is the spacing of repeater where is one of the project outcome of this project.

OptiSystem is a design and simulation software for fiber optics application. OptiSystem enables users to simulate/design next generation optical networks, current optical networks, SONET/SDH ring networks, amplifiers, receivers, transmitters. This software has many analysis tools eye diagrams, BER, Q-Factor, Signal chirp, polarization state, constellation diagrams, signal power, gain, Noise Figure, OSNR, data monitors, report generation, and more.

Objectives of Project

This project simulates and optimizes the performance parameters of EDFA. The objectives of this project are outlined as below:

• to increase output signal power .
• to flatten the gain of Erbium Doped Fiber Amplifier.
• to reduce the Amplified Spontaneous Emission (ASE) of Erbium Doped Fiber Amplifier .

Problem Statement

In order to have a high capacity transmission system, there are several ways such as by using wave-dense multiplexing(WDM) technique, increase the power of output transmission system, reduce the losses in transmission system and etc. By increase the number of optical amplifier in long haul transmission system is able to increase the output power of transmission system but this will increase the costs. Thus, the better solution is to optimize the performance of optical amplifier.

The output signal power is mainly affected by gain of the EDFA. The gain is affected by many factors which are the doping concentration and doping profile of the erbium doped fiber, length of the fiber, wavelength windows input signal, input powers and the pump power. The increase the input signal power certainly will increase the output signal power but the gain decreases. The wavelength

of input signal of EDFA can be in 1530nm to 1565nm (C-band) or 1570nm to 1605nm (L-band). The gain of C band is greater than L-band but the absorption is also large.

Amplified Spontaneous Emission Noise (ASE) of Erbium Doped Fiber Amplifier (EDFA) amplified together with the input signal. To obtain high output power, the Erbium Doped Fiber Amplifier (EDFA) need high optical pump power and high inversion. Thus, the higher inversion applied in EDFA, the higher the ASE noise. In the others word, Noise Figure will increase with the gain of EDFA.

Gain flatness is a function of inversion level. Typically 40% to 60% inversion leads to broadest gain with lowest ripple. The gain at the L band is flatter than C band but the C band has lower gain. The use of gain flattening filter can be a solution of gain flatness problem but it will decrease output signal power.

Scope of the Project

This project only involves the optimization of Erbium Doped Fiber Amplifier. The other types of optical fiber amplifiers are not involved. This project focuses on the simulation using software optisystem and does not involve any hardware. In addition, reduction of the noise covered in this project which covers Amplified Spontaneous Emission noise only and does not covers any others’ noises such as thermal noise, human noise and etc. The optimization of Erbium Doped Fiber output signal power is included in this project. This project is focus on the long haul transmission system where using the single mode fiber only.

Project Outcomes

In the end, The Erbium Doped Fiber Amplifier simulated with increased gain flatness. The Erbium Doped Fiber Amplifier simulated with high output power and

the spacing of repeaters were increased but the Erbium Doped Fiber Amplifier simulated have small amount of Amplified Spontaneous Emission.

Methodology

The basic information of optical fiber amplifier was obtained from the reference book and from internet sources. The information obtained is the basic configuration of optical amplifier in optical transmission link, advantages and disadvantages of Erbium Doped Fiber Amplifier, the Amplified Spontaneous Emission Noise (ASE) and etc. Second methods of data and information collections are from journal, magazine and reference books. The data and information is more advance such as the effect of ASE noise, analysis of gain flatness of EDFA, the relationship between ASE noise and pump power and etc.

Thesis Structure

Chapter 1: In this chapter, the objectives of the project were introduced. In overview of the project will introduce the basic idea of project and some basic knowledge related in this project. The problems and the expected outcome of this project were also stated.

Chapter 2: In this chapter, the research to background related of this project will be discussed. The concept structure of future work of this project will be come out by literature review. How to solve the problem stated in chapter 1 by applying the correct theory were explained in details.

Chapter 3: The procedures of solution to the stated problems in this project were explained in this chapter. The procedures that have been chose and the choice of procedures have to state in this chapter. The problems of problems’ analysis and collection of were included.

Chapter 4: The results of this project were show in this chapter. The results include simulation of the transmission link and analysis of the performance transmission link. The discussions

of the results also have to include.

Chapter 5: The objective, discuss the findings and conclude the limitation of this project are being justified in this chapter. Some recommendations on how to improve the project were discuss at the end of this chapter.

Literature Review

This chapter discussed all the useful theory and data about this project. The literature review was referring the journal, article, reference books and data sheet. These sources were collected from the library, internet and IEEE library website.

Introduction

Optical fiber has three main types of property which are dispersion, absorption, and scattering. These properties have cause attenuation, power losses, output power decrease where bring disadvantages to the long haul transmission. Dispersion occurs when the light travelling down a fiber optic cable “spreads out,” becomes longer in wavelength and eventually dissipates. Absorption is resulting by the impurities such as hydroxyl ions where will cause the optical power dissipated as heat power. Scattering is another major mechanism of attenuation in optical fiber. It happens when the light change direction or diffuse where caused by the light striking the small particles or the in-homogeneity of transmitting material.

Attenuation, a reduction in the transmitted power, has long been a problem for the fiber optics community. The increase in data loss over the length of a fiber has hindered widespread use of fiber as a means of communication. However, researchers have categorized three main sources of this loss: absorption, scattering, and, though it is not commonly studied in this category, dispersion.

With the demand for longer transmission lengths, optical amplifiers have become an essential component in long-haul fiber optic systems. An optical amplifier is a device that amplifies an optical signal directly,

without the need to first convert it to an electrical signal. By Optical amplifier, the capacity of optical transmission system is increases. Stimulated emission in the amplifier’s gain medium will cause amplification of incoming light.

Semiconductor optical amplifiers (SOAs), erbium doped fiber amplifiers (EDFAs), and Raman optical amplifiers lessen the effects of dispersion and attenuation allowing improved performance of long-haul optical systems. Optical amplifier Semiconductor optical amplifiers (SOAs), erbium doped fiber amplifiers (EDFAs), and Raman optical amplifiers lessen the effects of dispersion and attenuation allowing improved performance of long-haul optical systems.

OptiSystem

OptiSystem is a famous optical communication system simulation package for the design, testing, and optimization of virtually any type of optical link in the physical layer of a broad spectrum of optical networks, from long-haul systems to LANs and MANs. A system level simulator based on the realistic modeling of fiber-optic communication systems, OptiSystem possesses a powerful new simulation environment and a truly hierarchical definition of components and systems. Its capabilities can be easily expanded with the addition of user components and seamless interfaces to a range of widely used tools. There are many Models and Tools in Optisystem. The description of basic and relevant models or tools is show as below:

Erbium Doped Fiber

This model enables large and small input signal analysis, considering 980 nm or 1480 nm as wavelength pump. The numerical solution of the rate and propagation equations, assuming a two-level Er system, enables to design the amplifier in a co- or counter-propagating pump scheme. ASE is included in the simulations and fiber specifications such as geometrical parameters (for example, core radius, Er doping radius, Er metastable lifetime) as well as and absorption and

emission characterization (cross-section, fiber loss) are required as input files.

EDFA

The EDFA 1.0 designs Er-doped fiber amplifiers considering numerical solutions of the rate and the propagation equations under stationary conditions. The model includes amplified spontaneous emission (ASE) as observed in the amplifier Erbium Doped Fiber 1.0, however this module enables to the user selecting forward and/or backward pump as well as the pump power values.

Trapezoidal Optical

This model is an optical filter with a trapezoidal frequency transfer function.

Optical Filter Analyzer

This model can extract the frequency response of an optical component by comparing a reference optical signal before and after the calculation.

Optical source

There are 6 types of optical source:

• CW Laser
• Pump Laser
• White Light Source
• Laser Measured
• Laser Rate Equations
• LED
• Multiplexer and Demultiplexer

The WDM need the using of multiplexer and demultiplexer. In the Optisys, multiplexer and demultiplexer is a ideal multiplexer and demultiplexer.

Research Methodology

Chapter three explained the project methodology, approached taken and a closer look how the project was being conducted.

Understanding the project

There are three objectives of this project which are to increases the output signal power of the Erbium Doped fiber Amplifier (EDFA), to flatten the gain of the Erbium Doped Fiber Amplifier and reduce the Amplified Spontaneous Emission (ASE) of Erbium Doped Fiber Amplifier.

Literature review on the three objectives to finds out the methods to achieve the three objectives. The methods used in literature review are reviewing website’s information, reviewing journal and references book. The method of reviewing website’s information is for obtain the basic introduction on the fiber optic and Erbium Doped Fiber Amplifier. The second methods of reviewing journal and references books are to find out the methods of optimization the amplifier,

solutions of problems and etc.

The Transmission Link

The Figure 3.1 is the transmissions link that going to use in the project. The circuit is Erbium Doped Fiber Amplifier in multi-channels Wave Division Multiplexing (WDM) system. The WDM system used because the purpose of this project is to optimize the optical long haul transmission link system and the WDM is the necessary system in the long haul transmission link system.

There are 16 multiplexed signals which each channel spacing is 1nm. Most of the long haul transmission system such as Fiber to the Home system is using 16 or 32 channels in transmitter. At the receiver side, there are 16 channels output de-multiplexed by WDM de-multiplexer.

Output power of EDFA

The methods used to optimize the output power are by choosing the suitable parameters. The parameters are the input power and length of fiber. The input power selected is -23dBm for each channel (there are total 16 channels). Lastly, choosing C Band wavelength is one of the methods as C Band has larger gain property than L Band.

The gain of Erbium Doped Fiber amplifier is function of length of Erbium Doped Fiber. The erbium doped fiber length is set between 1m and 20m. The length of erbium doped fiber as the parameter to optimize EDFA’s gain because the EDFA’s gain increase dramatically with the length of erbium doped fiber.

The pump power was not chosen as the parameter to optimize the gain because pump power used as parameter for gain flatness of the EDFA.

Amplified Spontaneous Noise of EDFA

Since the Amplified Spontaneous Emission noise (ASE noise) is function of the gain, the noise figure was optimized by adjusting the gain of EDFA.

This method will limit the gain of the EDFA but it is more practical than the filtering method. The filtering method requires an optical filter to filter the noise but it is difficult and expensive to fabricate an optical filter [3].

The amplified spontaneous emission noise of EDFA was been observed and measured by noise figure of the EDFA system. The equation below [2] shows that noise figure is function of ASE noise and gain.

Measurement of the result

The results of this project will be analyzed by using dual port WDM analyzer. Dual port WDM analyzer is able to measure gain of EDFA, ratio of maximum and minimum gain and noise figure of the EDFA. The BER analyzer or eye diagram was used to measure the BER rate of each wavelength at receiver. The BER rate determines whether the EDFA designed is applicable in optical transmission system.

Conclusion

This Chapter will focus on the conclusion of the information contained in the report. This Chapter determine whether the objective is achieved.

In this report, the theory of the Erbium Doped Fiber Amplifier was described. Theory of parameters that influence the EDFA has been explained in detail. The nominal gain of the EDFA in this project is 36.3523dB. The gain flatness of the EDFA designed is A±0.695285dB and the maximum noise figure of the EDFA is 4.00012dB.

The typical gain of the EDFA is 30dB. However, the typical noise figure and gain flatness of an EDFA are 5.5dB and A±0.8dB. The EDFA designed in this project has been optimized from the typical specification as mentioned above. The gain was optimized 30 percent from the typical gain of EDFA. Whereas, the noise figure of

EDFA optimized to 37.50 percent. The gain flatness was optimized in 15.06 percent.

The Erbium Doped Fiber Amplifier designed in this project can be optimized by further research in future.

Optisystem (Amplifier Edition) was being recommended to use as the simulator to optimize the Erbium Doped Fiber Amplifier. The simulator Optisystem (Amplifier Edition) is more professional in optimization of the Optical Amplifier.

The gain flatness of Erbium Doped Fiber Amplifier can be optimized by using Automatic Gain Control. The automatic gain control system is a feedback system which able adjusting the gain of amplifier. Thus this will maintain the gain flatness of the Erbium Doped Fiber Amplifier. This can be simulated by using the Simulator of Optisystem (Amplifier Edition). The Automatic Gain Control system is an electronic device thus it can be done in hardware.

The Optical Amplifier, EDFA can be designed with its own core diameter or Numerical Aperture to get the optimum performance in practical. The core diameter of Erbium Doped Fiber is function of Gain and Noise figure.

The designed EDFA was done by simulation; this project was recommended fabricated to hardware.