ANALYSIS OF DWDM SYSTEM USING DIFFERENT MODULATION AND COMPENSATION TECHNIQUE AT DIFFERENT BIT RATES MEENAKSHI SHARMA 1,NAVPREET KAUR 2 1 MTech Scholar,Deptt. Of ECE,IET Bhaddal,Punjab 2 Assistant Professor,Deptt. Of ECE,IET Bhaddal,Punjab Abstract: Dense wavelength division multiplexing (DWDM) is a fiber optic technology that can transmit multiple information streams simultaneously over the single fiber. In this paper we are doing comparative analysis of 16 channels Dense wavelength division multiplexing (DWDM) system using different modulation formats (NRZ, RZ ) and compensation schemes at different bit rates (10Gbps, 30Gbps and 60Gbps) with standard and dispersion compensated fiber on the basis of Q-factor, eyediagram and bit error rate for fixed gain EDFA and length both type of fiber. Keywords: DWDM, NRZ, RZ,Quality factor. I. INTRODUCTION The core of the global telecommunication network consists of wavelength division multiplexed (WDM) optical transmission systems. A WDM transmission link transport large amount of data traffic by multiplexing a number of lower capacity wavelength channels onto a single fiber. The use of WDM therefore allows increase in the capacity of long haul optical transmission systems or, decrease in the (10Gbps, 30Gbps, 60Gbps) with standard and dispersion compensated fiber on the basis of Q- factor, eye-diagram and bit error rate for fixed gain EDFA and length both type of fiber[3].in differnts modulation formats of transmitter In section III, described the methodology and simulation parameters and fiber parameters we are using. Section IV is result and section II, we are described discussion in which we are doing comparative study of DWDM optical communication system with different modulation formats at different bit rates. In the end section V, conclusions are made.cost of the transmitted bandwidth, i.e. the cost per transmitted bit. In long-haul WDM transmission systems there occurs nonlinear impairments.to build robust long-haul transmission systems at high bit rates these transmission impairments should be optimized &, if possible, compensated. It is beneficial to space WDM channels as closely as possible since all shared optical components operate within the limited wavelength window. In dispersion- managed systems utilizing single- mode fiber (SMF) and dispersion compensating fiber (DCF),the positive dispersion of single- mode fiber can be compensated by the large negative dispersion of dispersion compensating fiber (DCF)[1][].By using advanced modulation formats along with dispersion compensation schemes performance and tolerance of system can be increased. Advanced Modulation formats are very important to improve the spectral efficiency as bit rate of system gets higher.in this paper we are doing comparative analysis of 16 channels dense wavelength division multiplexing (DWDM) system using different modulation formats (NRZ, RZ) and compensation schemes at different bit rat II.MODULATION FORMATS A. NRZ Format Fig.1 (a) shows the schematic of NRZ transmitter. It is a type of amplitude shift-keying. ISSN 2394-0573 All Rights Reserved 2015 IJEETE Page 219
Traditionally, NRZ modulation format has been widely used format. Figure 1(a) NRZ Transmitter B. RZ ( return-to-zero) Format Fig.1 (b) shows the schematic of RZ transmitter. It has narrow optical spectrum then the conventional RZ format and high tolerance to group velocity dispersion (GVP) and mixed effect of self phase modulation (SPM)[8]. Figure 1(b) RZ Transmitter III. METHODOLOGY We are using Optisystem 10 for simulation and designing.it is an innovative, powerful and rapidly evolving software design tool. It enables users to test, plan and simulate almost all type of optical link. Below Fig.2 shows the Post compensation scheme of 16 channel DWDM system which is consist of transmitter, fiber and receiver. Figure 2 Post Compensation Scheme Transmitter has CW laser array with 16 output ports which has equally spaced emission frequency range from 191.5-194.5 THz, data modulator and the optical multiplexer. Data modulators are connected to each ouput port of CW laser array then signals from data modulator is fed to 16 input ports optical multiplexer having bandwidth 30GHz.loop control after multiplexer, EDFA (Erbium doped fiberamplifier) is placed after every fiber to compensate the losses of the fiber with constant noisefigure. Signals are demultiplexed with demultiplexer and at the end we use photodetector,low pass filter and BER analyser to find out the output.in post compensation scheme DCF fiber is placed after SMF to compensate the dispersion and nonlinearities and two inline EDFA are used. Table 1 shows the simulation parameters and Table 2 shows the fiber parameters used in the DWDM system. Table 1. Simulation Parameter Bit rate 10Gbps,30Gbps,60Gbps Sequence length 64 Samples per bit 256 30 GHZ Bandwidth Central frequency 191.5THZ of 1st channel Capacity 16X 10Gbps,16X30Gbps,16X60Gb ps Table 2. Fiber Paramater ISSN 2394-0573 All Rights Reserved 2015 IJEETE Page 220
SMF DCF Attenuation(dB/Km) 0.2 0.5 Length(km/span) 100 20 Dispersion(ps/Km-nm) 17-85 Differential group delay( 0.2 0.2 ps/km) 2 Effective Area m 80 22 Fig.4 shows Q-factor and BER of post- dispersion compensation scheme at 30Gb/s using modulation formats: (a) NRZ, (b)rz Fig.5 shows Q-factor and BER of post- dispersion compensation scheme at 60Gb/s using modulation formats: (a) NRZ, (b) RZ IV RESULTS AND DISCUSSION Below figures shows the simulated results of 16 channels of DWDM optical communication system. This system is analysed for post compensation at different bit rates.in this paper we are doing comparative analysis of 16 channels Dense wavelength division multiplexing (DWDM) system using different modulation formats (NRZ,RZ) and Post compensation at different bit rates (10Gbps, 30Gbps, 60Gbps) with standard and dispersion compensated fiber on the basis of Q-factor, eye-diagram and bit error rate for fixed gain EDFA and length both type of fiber. On the basis of simulate result we can say advanced modulation formats plays very important role. As we increases bit rate, quality factor start to decreases and bit error rate increases. At high speed advanced modulation formats and dispersion compensation scheme gives better results. Table 3 Different modulation formats having Q factor and BER Figure 3(a) Figure 3(b) Fig.3 shows the Q-factor and BER of Post- dispersion compensation scheme at 10Gb/s using modulation formats: (a) NRZ, (b) RZ Fig.3 shows the Q-factor and BER of Postdispersion compensation scheme at 10Gb/s using modulation formats: (a) NRZ, (b) RZ Figure 4 (a) ISSN 2394-0573 All Rights Reserved 2015 IJEETE Page 221
dispersion compensation scheme using DCF using different modulation system NRZ, RZ at different bit rates 10Gbps, 30Gbps and 60 Gbps. We observed that at high bit rate RZ format gives better performance on the basis of Q factor, bit error rate (BER) and eye opening.in this we can say that RZ modulation format is faithful for long distance communication.in RZ format we get higher Qfactor and lower bit error. Figure 4(b) Fig.4 shows Q-factor and BER of post- dispersion compensation scheme at 30Gb/s using modulation formats: (a) NRZ, (b)rz Figure 5(a) Figure 5(b) Fig.5 shows Q-factor and BER of post dispersion compensation scheme at 60Gb/s using modulation formats: (a) NRZ, (b) RZ V. CONCLUSION In this paper we have analysed 16 channels DWDM optical communication system for post REFERENCES [1]Govind P. Agrawal, Fiber-optic communication systems, Third edition, 2002, John Wiley & Sons, Inc, ISBN: 0-471-21571-6. [2]Gerd Keiser, Optical fiber communications, third edition, 2000, McGraw- Hill Higher Education, ISBN: 0-07-116468-5. [3] Gupta, S.; Shukla, N. K.; Jaiswal, S., "Pre-, post, symmetric1 and 2 compensation techniques with RZ modulation," Recent Advances in Information Technology (RAIT), 2012 1st International Conference on, vol., no.pp.251,255, 15-17 March 2012. [4]Buckley Sean Beyond-100G, Fujistu network communications inc. [5 ] R. Llorente, R. Clavero, F. Ramos, J. Marti, Linear and nonlinear crosstalk evaluation in DWDM networks using optical Fourier transforms, EURASIP Journal on Applied Signal Processing Volume 2005, 1 January 2005, Pages 1593-1602. [6] Van den Borne, D.; Jansen, S.L.; Gottwald, E.; Krummrich, P.M.; Khoe,G-D; de Waardt, H., "1.6-b/s/HzSpectrally Efficient Transmission Over 1700 km of SSMF Using 40 85.6-Gb/s POLMUX-RZ-DQPSK," Lightwave Technology, Journal of, vol.25, no.1, pp.222,232, Jan. 2007. [7] D. van den Borne, Robust optical transmission systems, Technische Universiteit Eindhoven, ISBN 978-90-386-1794-7 2008. [8] Anjali Singh, Modulation formats for high speed, long haul fiber optic communication systems, Inphi corporation. [9] Kahn, J.M.; Keang-Po Ho, "Spectral efficiency limits and modulation/detection techniques for ISSN 2394-0573 All Rights Reserved 2015 IJEETE Page 222
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