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Article
Phase Noise Compensation for Coherent Orthogonal Frequency Division Multiplexing in Optical Fiber Communications Systems

Author: J.K. Hmood
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2009 Volume: 5 Issue: 2 Pages: 3-10
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this paper, the Coherent Optical (CO) systems using Orthogonal Frequency Division Multiplexing (OFDM) for dispersion compensation is demonstrated. The Quadrature Amplitude Modulation QAM-OFDM transmitter signal was controlled by the Mach-Zender Modulator (MZM) which modulates the laser source with wavelength of 1550nm. The heterodyne receiver with dual-polarization optoelectronic down-converter is used to obtain good coherent detection without using optical phase locked loop. The analytical part was done using a software simulator. All the proposed system components were simulated using VPIphotonic simulation software for testing CO-OFDM system. The transmitted signal, optical spectrum, eye diagram and constellation diagram was obtained to evaluate system performance.


Article
Novel Optical Fiber Sensor Based on SGMS Fiber Structure for Measuring Refractive Index of Liquids and Gases

Author: J.K. Hmood
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2011 Volume: 7 Issue: 4 Pages: 17-21
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

In this paper a single mode-gap-multimode-single mode fiber structure (SGMS) as refractive index sensor is demonstrated. A beam propagation method (BPM) for the circular symmetry waveguide is employed for numerical simulations of the light propagation performance in such fiber devices. The multimode interference effect is revealed to design optical fiber sensor with reasonable linearity in wide range of refractive indices. A simple way to predict and analyze the spectral response of the SGMS structure is presented with the derived approximated formulations. The proposed sensor is realized by using standard optical fibers.Results indicate that the proposed SGMS structure can be exploited for measuring a broad refractive index range with reasonable high resolution. The results achieved for refractive indices in the range of 1.1 to 1.43 have best linearity with correlation coefficient 0.9991 at wavelength of 1550 nm. Therefore, it can be suggested that the SGMS structure fibers are attractive for measuring refractive index of both gases and aqueous solutions such as chemical liquids, biological, and biochemical sensing.

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