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Int. J. Elec&Electr.Eng&Telecoms. 2015 Sunil K Panjeta, 2015 Research Paper ISSN 2319 2518 www.ijeetc.com Special Issue, Vol. 1, No. 2, July 2015 National Conference on Emerging Trends in Electronics & Communication (ETEC-2015) 2015 IJEETC. All Rights Reserved NOISE FIGURE AND GAIN OPTIMIZATION OF MULTISTAGE EDFA FOR DIFFERENT FIBER LENGTH AND PUMPING POWER Sunil K Panjeta 1 * *Corresponding Author: Sunil K Panjeta, panjetasunil@gmail.com Information revolution implies that multimedia networks need high bandwidth real-time communication services. At present, optical fiber is the only transmission medium offering such large bandwidth with low loss communication links. To amplify an optical signal with a conventional repeater, one performs photon to electron conversion, electrical amplification, retiming, pulse shaping, and then electron to photon conversion. Although this process works well for moderate speed single wavelength operation, it can be fairly complex and expensive for high speed multiple wavelength systems. Thus a great deal of effort has been expended to develop all-optical amplifiers. These devices operate completely in the optical domain to boost the power levels of multiple light wave signals over spectral bands of 30 nm. Optical amplifiers are in general bit rate transparent and can amplify signals at different wavelength simultaneously. Optical amplifiers are mainly classified into travelling wave s semiconductor optical amplifier, fabry-perot semiconductor optical amplifier, Erbium doped fiber amplifier, Raman & Brillouin fiber amplifiers. In this, analyzed the performance of augmented gain EDF amplifier systems by enhancing the stages of EDF amplifier and further by variation in pumping power on designed EDF amplifier system. The length of doped fiber in EDFA is also effected. The design evaluates the performance of the network for a given pattern specifies the design accessibility for the speed enhancement. The Performance of an Optical Communication system can be improved by the use of EDFAs as an Optical Amplifier. Erbium Doped Fiber Amplifier (EDFA) is an important element in DWDM networks. For the present work, we have used EDFA design software tool. The proposed model consists of an input source, isolator, pump source, erbium fiber and WDM coupler. It simulates various characteristics such as amplified spontaneous emission, minimum gain, maximum gain, average gain, noise figure, gain flatness, gain tilt etc. in efficient manner. It confirms the excellent agreement between simulations and results obtained in real EDFA design. And also changing the design parameters on four stages EDF amplifier such as Input Pump Power, doped fiber length the different performance parameters (gain and noise figure) can be optimized without changing the values of isolator, erbium fiber length and WDM. 1 Asstt. Professor, Dept. of Electronics & Communication Engg., YIET, Gadholi, Yamunanagar, Haryana, India. 148
INTRODUCTION Optical Amplifier An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. Different types of optical amplifiers: Optical amplifier can serve several purposes in the design of optical fiber communication systems. An important application for long haul transmission systems is in replacing the electronic generators with optical amplifiers which can amplify several channel simultaneously. Such a replacement can be carried out as long as the cumulative effects of dispersion and optical noise do not limit the system performances. W hen amplifiers are used to replace electronic generator, they are called in-line amplifiers. This is the most widely used type of amplifier since every system needs many of those. Another way to use optical amplifiers is to increase the transmitter power by placing an amplifier at the transmitter output. Such amplifiers are called booster amplifiers The last application is an increase in receiver sensitivity achieved by placing a high gain low noise amplifier at the receiver input. Such amplifiers are called preamplifiers There are several types of optical amplifiers which are based on different physical principles. The most widely used amplifiers are known as EDFA (Erbium Doped Fiber Amplifier) which are based on the use of excited Erbium ions placed in the core of a fiber. They operate near 1550 nm. Other ions can be used to amplify in other optical band but none work as well as Erbium. Semiconductor Optical Amplifiers (SOA), which are semiconductor lasers where the mirror feedback has been eliminated, are also based on the population inversion principal. They operate in the 1300 and 1550 nm regions and can also be used for optical signal processing since they are highly nonlinear. These amplifiers have an intrinsic bandwidth limitation (30 nm for the C band EDFA and the bulk SOA). While Erbium Doped Fiber Amplifiers (EDFA) will continue to dominate fiber optics systems, other optical amplifiers are emerging. Most noticeable are Raman and Parametric fiber amplifiers, two amplifier types whose operational principles are based on two nonlinear processes (SRS and FWM respectively). They can be used to achieve wide bandwidths that can be used anywhere within the fiber bandwidth since the fundamental spectroscopic properties of the materials providing the gain do not play a role. The optical fiber can be doped with any of the rate earth element, such as Erbium (Er), Ytterbium (Yb), Neodymium (Nd), or Praseodymium (Pr) the host fiber material can be either standard silica, a fluoride based glass or a multi component glass. The operating regions of these devices depend on the host material and doping elements. Fluorozirconate glasses doped with Pr or Nd are used for operation in the 1300 nm window, since neither of these ions can amplify 1300 nm signals when embedded in silica glass. The most popular material for long haul telecommunication applications is a silica fiber doped with Erbium, which is known as a EDFA. In some cases, Yb is added to increase the pumping efficiency and the amplifier gain.the operation of an EDFA by itself normally is limited to the l530-1560 nm region. The active medium in an optical fiber amlifier consists of 149
a nominally 10-30-m lenght of optical fiber that has been lightly doped with a rare earth lement, such as erbium (Er), ytterbium (Yb), thulium (tm) the host fiber material can be standerd silica, a fluoride-based glass, or a tellurite glass. Doped Fiber Amplifiers Doped Fiber Amplifiers (DFAs) are optical amplifiers that use a doped optical fiber as a gain medium to amplify an optical signal. They are related to fiber lasers. The signal to be amplified and a pump laser are multiplexed into the doped fiber, and the signal is amplified through interaction with the doping ions. The most common exampleis the Erbium Doped Fiber Amplifier (EDFA), where the core of a silica fiber is doped with trivalent Erbium ions and can be efficiently pumped with a laser at a wavelength of 980 nm or 1,480 nm, and exhibits gain in the 1,550 nm regions. An Erbium-Doped Waveguide Amplifier (EDWA) is an optical amplifier that uses a waveguide to boost an optical signal. Amplification is achieved by stimulated emission of photons from dopant ions in the doped fiber. The pump laser excites ions into a higher energy from where they can decay via stimulated emission of a photon at the signalwavelength back to a lower energy level. The excited ions can also decay spontaneously (spontaneous emission) or even through nonradioactive processes involving interactions with phonons of the glass matrix. These last two decay mechanisms compete with stimulated emission reducing the efficiency of light amplification. The amplification window of an optical amplifier is the range of optical wavelengths Figure 1: Schematic Diagram of a Simple Doped Fiber Amplifier for which the amplifier yields a usable gain. The amplification window is determined by the spectroscopic properties of the dopant ions, the glass structure of the optical fiber, and the wavelength and power of the pump laser. Basic Principle of EDFA A relatively high-powered beam of light is mixed with the input signal using a wavelength selective coupler. Theinput signal and the excitation light must be at significantly different wavelengths. The mixed light is guided into asection of fiber with erbium ions included in the core. This high-powered light beam excites the erbium ions to theirhigher-energy state. When the photons belonging to the signal at a different wavelength from the pump light meet theexcited erbium atoms, the erbium atoms give up some of their energy to the signal and return to their lower-energystate. A significant point is that the erbium gives up its energy in the form of additional photons which are exactly in the same phase and direction as the signal being amplified. So the signal is amplified along its direction of travelonly. This is not unusual - when an atom lases it always gives up its energy in the same direction and phase as theincoming light. Thus all of the additional signal power is guided in the same fiber mode as the incoming signal. There is usually an isolator placed at the output to prevent reflections returning from the attached fiber. 150
Such reflections disrupt amplifier operation and in the extreme case can cause the amplifier to become a laser. Figure 2: Dual Stage EDF Optical Amplifier Design SOFTWARE USED In the desiging of the EDF optical amplifier required software is Gain Master EDF-OPTICAL AMPLIFIER DESIGN EDFA optical amplifier designing is done with help of the Fiber Optical Simulation Program and the Gain Master. Design tools are used. In this design we show that the optical amplifier gives all the parameter of the erbium fiber and that gives the idea how the signal is to be transfer from one location to the other location. In this design we find the gain, wave length and noise parameter. The software allows for schematic representations of an optical amplifier to be input via a graphical user interface which mimics the symbolic language often used by engineers to outline a design on paper. The program tracks the optical power through the design, integrating the differential equations to solve the propagation of signal, pump, and Amplified Spontaneous Emission (ASE) bands through all erbium fiber sections. Once a simulation is complete, the user may look inside the design by graphing the power propagating through any fiber in the design, as well as through the length of all erbium fiber sections. Also, by use of the probe component, the user may make common two-point Figure 3: Four-Sstages EDF Optical Amplifier Design 151
Figure 4: Simulation Results of Four-Stage EDF Optical Amplifier by Gain Master measurements of interest, such as gain, noise figure, conversion efficiencies, etc. Probe result snapshot of simulation software used, Gain master is shown in Figure 4. Optical parameters of any component may be changed and the simulation re-run to observe the ef f ects on amplif ier performance. ERBIUM PARAMETERS ANALYSIS Effect on Enhancing the Stages from Second to Fourth of EDFA In this we have shown the variation of gain and noise with respect to wavelength by enhancing the stages of EDFA from 2 nd stage (Figure 2) to 4 th stage by assembling the optical blocks isolator, WDM, Erbium doped fiber and were added to compose the complete 4 th stage EDFA system shown in Figure 3 and then simulated with the help of simulator Gain Master and tabulated the parameter values. The effect of increase the no. of stages on noise figure and gain is considered, shown in Figures 5 and 6. The tabulate effect can be seen from Table 1. Figure 5: Noise Figure Spectrum of EDF Optical Amplifier (a) Single-Stage, (b) Dual Stages, (c) Four-Stage 152
Figure 6: Gain Spectrum of EDF Optical Amplifier (a) Single-Stage, (b) Dual-Stages, (c) Four-Stages Table 1: Analysis of EDFA Gain, Noise Figure with Single-Stage, Dual-Stage and Four-Stage EDF Optical Amplifier Figure 7: Gain Spectrum of EDF Optical Amplifier on Effect of Input Pumping Power (0.12 W, 0.35 W, 0.55 W, 0.85 W) Effect of Pumping Power on Designed EDFA The optical parameters, Gain and noise figure has been analyzed on designed system 4 th stage EDFA with different pumping power. Figures 7 and 8 shows the gain spectrum and Noise figure spectrum of EDFA on different pumping power 0.12 W, 0.35 W, 0.55 W, 0.85 W respectively. As the pump power increases, gain increases while the Noise figure decreases, however gain flatness increases along with Figure 8: Noise Figure Spectrum of EDF Optical Amplifier on Effect of Input Pumping Power (0.12 W, 0.35 W, 0.55 W, 0.85 W 153
Table 2: Analysis of EDFA Gain, Noise Figure by Variation of Pumping Source Power the increase in pumping power (tabulated in Table 2). Effect of Doped Erbium Fiber Length on Designed EDFA The parameters Gain and Noise figure has been measured with different Lengths 10 m, 20 m, 30 m and 50 m from the designed simulation models and that has been plotted as shown in Figures 9 and 10 and tabulated in Table 3. Figure 9: Noise Figure Spectrum of EDFA in Four-Stage Design When Doped Erbium Fiber Length Used is (a) 10 m, (b) 20 m, (c) 30 m, (d) 50 m Figure 10: Gain Spectrum of EDFA in Four-Stage Design When Doped Erbium Fiber Length Used is (a) 10 m, (b) 20 m, (c) 30 m, (d) 50 m 154
Table 3: Analysis of EDFA Gain, Noise Figure with Effect of Length of Doped Erbium Fiber As the doped Erbium fiber length increases from 1 m to 20 m gain increases but above 20 m it starts decreases, as shown in graph with fiber length 30 m, 50 m conclude that doped fiber length must lies between 1 m to 20 m. CONCLUSION This paper shows that the optical amplifier is to be used for amplify the signal and basically designed an optical amplifier to increase the level of the input signal and found that the optimum parameters for the transmission of the data. The input wavelength is taken in between 1520-1617nm. Moreover it also shown the noise spectrum of the erbium doped optical amplifier. Wavelength Division Multiplexing (WDM) technique is used for the multiplexing of the signal. It shows the results of the fourth stage of the optical amplifier and the different optimum parameters of the optical amplifiers. optical amplifier up to the threshold value the gain increases after that the gain decreases with wavelength and becomes zero at the peak value of wavelength on the similar pattern the noise also 1 st increases and then decreases and finally becomes zero at the peak wavelength. Pumping power effect on EDF amplifier is analyzed Simulation Results indicate that Gain and noise figures are affected by pump power. It may be observed that the Gain is optimized and Noise Figure initially decreases with increase in Pump Power and then attains the same value. The doped Erbium length in the EDFA design is also analyzed with results of length taken 10 m, 20 m, 30 m and 50 m and found that the optimized gain in range 10 m-20 m, after that gain decreases with increasing of doped erbium fiber length in EDFA design. REFERENCES 1. Aditya Goel and Ravi Shankar Mishra (2010), Design of Broadband EDFA for Next Generation Optical Network, International Journal of Neural Networks and Applications, January-June, pp. 9-13. 2. Berkdemir Cuneyt et al. (2009), On the Temperature-Dependent Gain and Noise Figure Analysis of CB and High- Concentration EDFAs with te Effect of Cooperative Upconversion, IEEE Journal of Lightwave Technology, Vol. 27, No. 9. 3. Farah Diana Binti Mahad and Abu Sahmah Bin Mohd Supa a (2009), EDFA Gain Optimization for WDM System, Faculty of Electrical Engineering Universiti Teknologi, Vol. 11, No. 1, pp. 34-37, Malaysia. 4. Harun S W, Samsuri N N and Ahmad H (2004), Partial Gain Clamping in Two Stage Double Pass L Band EDFA Using a Ring Resonator, IEEE. 5. Jang J H, Jung J H and Lee K K (1999), Implementation of Automatic Gain Controlled Bidirectional EDFA in WDM Networks, IEEE CLEO/Pacific Rain. 155
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