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تقييم اداء الكشف المباشر والمتشاكه في نظام اتصال الليفة الضوئية == Performance Evaluation of Direct And Coherent Detections In Optical Fiber Communication System
Author name:
علاء عبد الزهرة جعفر
Supervisor name:
علي يوسف فتاح
General topic:
Electrical, Electronic and Communications Engineering
Specific topic:
Electronics and Communications Engineering
Degree:
Master
University:
University of Technology - Electrical Engineering Department - Electronic Engineering Branch
Language:
English
University location:
Baghdad
First pages:
34T504 - p.pdf
Abstract:
تطورت خدمات الاتصالات بشكل متسارع في السنوات القليلة الماضية خصوصا في المسافات بعيدة المدى وبمعدل نقل البيانات بدقة عالية وخسائر قليلة في جميع انحاء العالم. وقدمت تقنيات مختلفة لزيادة سعة الارسال في انظمة اتصالات الالياف الضوئية بواسطة جمع مسارات البيانا | In recent years, there has been an extensive development of optical fiber services. They provide transmission over long distances at a high data rate with few losses all over the world. Different techniques have been introduced to increase the transmission capacity of optical fiber communication systems by a multiplexed high data rate stream into an optical fiber such as Dense Wavelength Division Multiplying (DWDM) technique. Since the deployment of DWDM technique, the focus on introducing large system capacity with high system performance, different detection techniques have been introduced to enhance the system performance with high sensitivity. In this work, two types of detection techniques (direct and coherent detection) have been evaluated and compared with each other. These detection techniques have been evaluated based on several models of encoding format such as Return to Zero - Differential Phase Shift Keying (RZ - DPSK) and Non Return to Zero - Differential Phase Shift Keying (NRZ - DPSK) at 10 Gb/s as a data rate.These systems were first simulated with a single channel to analyze the performance with no Stimulated Raman Scattering (SRS), Cross Phase Modulation (XPM) and Four Wave Mixing (FWM) effects. Whereby the system of 8×10 Gb/s is simulated at 200 GHz, 100 GHz and 50 GHz as channel spacing. Three types of dispersion compensation schemes are used in the link channel. These systems are simulated using (Optisystem version 10.0) software package. The performance of the designed systems are evaluated through Q.factor verses input power and Bit Error Rate (BER) verses Signal to Noise Ratio (SNR).The polarization interleaving is used with the WDM systems to decrease the nonlinear effects and the crosstalk arising among the adjacent channels.The obtained results of the 67% RZ - DPSK arrived to the threshold power at input power less than of the 50% RZ - DPSK, as well as the 50% RZ - DPSK system arrived to maximum Q.factor lower than 33% RZ - DPSK. This is due to the pulse duration of 33% RZ - DPSK is smaller than of 50% and 67% RZ - DPSK.The results show that the coherent detection technique has better performance than the direct detection technique. The coherent detection technique has Q.factor equal to 45, while the direct detection has Q.factor equal to 27 at the same input power ( - 5dBm), while the coherent detection technique arrived to the threshold power at the input power less than of the direct detection technique.The BER of the 33% RZ - DPSK with coherent detection with 10 Gb/s at 300 km as transmission distance achieved ?10?^( - 12.9) at SNR of 10 dB, while for the 33% RZ - DPSK with direct detection is achieved a BER of ?10?^( - 8.8) with SNR of 10 dB.The performance of the proposed systems has been improved extrusivly with increase the space channel, where the performance of the systems at 200 MHz as channel spacing has best performance than 50 MHz as channel spacing.By adapting coherent detection with 33% RZ - DPSK technique of 200 MHz as channel spacing, DWDM system can carry high data rate with long - haul transmission distance.
