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The Log Normal model for weak turbulences and Gamma-Gamma model for moderate to strong turbulences are being used for calculating the path losses for engineering Free Space Optical (FSO) communication link. Since FSO has been an attractive substitute to overcome the issues of RF spectrum license, high infrastructure cost and difficult terrains to ensure the availability of a network. Their application in mountainous and high density built up areas needs to be exploited. Atmospheric turbulence degrades the FSO communication performance arising due to variations in C n 2 (Refractive index structure parameter). Both these models have the limitation of NOT considering Rainfall parameter while calculating C n 2 . In this present paper we have included effect of Rainfall and presented the modified analytical model by re modeling C n 2 . To validate the impact, comparison of existing model and the modified path loss model has been presented using Meteorological (MET) data for a designed FSO communication link between geographically known mountainous locations of North eastern region of Arunachal Pradesh. The results emphasize that, the modified model is essential to ensure reliable and fail safe FSO link. [ABSTRACT FROM AUTHOR]

Application of fiber Bragg grating (FBG) in optical communication is an evolving field. In this research paper, various types of chirped FBG's (CFBG) have been used with avalanche photodiode (APD) on the designed optical fiber communication (OFC) link. Data rate of 20 Gbps and return-to-zero modulation format has been kept as fixed parameters. The designed link has been evaluated for varying fiber lengths (100, 200, 300, 400 and 500 km), various type of CFBG's (linear, quadratic, square root and cubic root) with Gaussian apodization function, varying grating lengths (10, 20, 30, 40 and 50 mm) and operating temperatures (5°C, 10°C, 15°C, 20°C, 25°C, 30°C). The designed OFC link has also been evaluated for APD with and without CFBG. The performance evaluation matrix parameters selected are Q-factor, bit error rate and eye diagram. The OFC link employing CFBG with APD has been found to be superior. In compensating chromatic dispersion, optimum results have been observed for linear CFBG with Gaussian apodization function in comparison to other types of CFBG with 50 mm grating length for the maximum transmission distance. [ABSTRACT FROM AUTHOR]

Orthogonal Frequency Division Multiplexing (OFDM) is one of the popular techniques used for 4 G, 5 G and backbone optical communication networks to meet the large data transfer requirement applications. Optical Communication model based on Coherent Optical OFDM (CO-OFDM) using 4-Quadrature Amplitude Modulation (QAM), 16-QAM and 64-QAM has been evaluated by different researchers. To understand and evaluate the effects of polarization, we have proposed an Optical Communication model with Polarization Division Multiplexing (PDM). The proposed CO-OFDM PDM system has been evaluated for different link lengths of 50, 100 and 150 km at varying data rates of 10, 20 and 30 Gbps. The performance of the designed link has been evaluated in terms of Q-factor, Bit Error Rate (BER), Optical Spectrum and constellation diagram. The results clearly exhibit that the Q-factor, BER and constellations are superior when PDM is incorporated with the CO-OFDM link using X-QAM. [ABSTRACT FROM AUTHOR]

Free space optical (FSO) communication is coming up as an attractive alternative to solve the connectivity hindrances. It is an efficient optical technology having several advantages such as narrow beam size, unlicensed spectrum, high reliability, huge modulation bandwidth, low power and higher grade of security. In this paper, we have proposed an FSO communication system model using EDFA-EDFA hybrid optical amplifier (HOA) configuration which provides enhanced reach and higher data rate. For transmitting channel, weak turbulence approximation which exhibits log-normal statistics is considered. Q-factor, bit error rate (BER) and Eye diagram have been taken as performance metrics. From simulative results, it has been observed that the designed FSO communication system efficiently enhances the transmission reach from 1,000 to 5,000 m along with a substantial improvement in Q-factor and BER. [ABSTRACT FROM AUTHOR]

The optical fiber communication offers a huge bandwidth for data transmission at higher data rates but to increase the throughput for long-haul networks, metro data links, and data centers, additional fiber is required which is not economical. For effective reception of signals at the receiver, the photo detector in optical communication requires higher efficiency, lower noise, ultrafast response and optimum received signal strength. The inherent dispersion and nonlinear impairments in optical fiber communication system can be overcome by using the Fiber Bragg Grating (FBG) which is a Dispersion Compensating Module. FBG helps to improve the long-haul transmission by providing an efficient system performance. This paper presents a detailed review of FBG and photo detectors and their use in an Optical communication system. This paper will help the researchers to find useful material at a single platform. [ABSTRACT FROM AUTHOR]