Informatics Publishing Limited

N. Sangeetha ¹, A. Brintha Therese ¹, G. Aarthi ¹

Affiliations
1 School of Electronics Engineering, Vellore Institute of Technology University, Tamilnadu-632 014, IN

Abstract

Free-space optics (FSO) is a wireless line of sight technology that transmits high data rates using a narrow beam light through the air as transmission medium. The demands on bandwidth and spectral availability are endless. Many telecommunications providers have been deploying different types of access technologies, such as cable and fixed wireless, in order to fulfill the needs. In many cases, transmission using fiber optics is preferred due to their ability to send high data rates with high reliability. This paper shows that the Free-space optics technology is an alternative to the already established fiber optics technology. The main reasons are it requires less installation time and it can save the required costs significantly without losing the capability to send high data rates. The paper also presents an assessment on the performance and current state of the Free Space Optics technology. It represents FSO’s limits in use under certain conditions; there are also circumstances where it can provide a high speed secure transmission channel.

Keywords

FSO, Last Mile Solutions, OWC, RF.

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S. J. Grace Shoba ¹, A. Brintha Therese ¹

Affiliations
1 SENSE, VIT University, Chennai, IN

Abstract

Medical image analysis is important for early detection of several diseases related to the eye. The retinal fundus photographs are widely used in the diagnosis and treatment of various eye diseases such as diabetic retinopathy, glaucoma etc. Retina can be analyzed by detecting the features such as blood vessels, optic disk, macula, fovea, etc. The fovea is a small, slightly concave area without retinal capillaries and its detection is very important for ocular diagnosis systems. It appears as a dark area, in contrast to the rest of the retina where retinal vessels are enhanced by the fluorescent liquid. The fovea is so important because some specialized cells that provide central vision lie in it. This paper describes an automated detection of fovea. Detection of fovea is dependent upon approximate location of Optic Disk.Initially the retinal blood vessels is detected using mathematical morphology. Since the optic disk is usually the brightest component on the fundus, the high intensity value of pixels is used to locate it. From these values the highest pixel value is determined which is considered as the centre of the optic disc. Using this, the position of the optic disk is located approximately using the simple circular fitting method. Geometrical features are then used to localize the macula region successfully. The centre of the macula is the localized fovea region.

Keywords

Circular Fitting, Fovea, Macula, Mathematical Morphology, Retina.

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N. Subhashini ¹, A. Brintha Therese ¹

Affiliations
1 VIT University, Chennai – 600127, Tamil Nadu, IN

Abstract

To tackle tremendous growth in the network traffic, EPON (Ethernet PON Networks) based on Time Division Multiplexing (TDM) is being used. There is a need for a Dynamic Bandwidth Allocation (DBA) algorithm to control the flow of sequence of data among the subscribers. In this paper a new user prioritized Dynamic Bandwidth Allocation (DBA) algorithm is demonstrated. Depending on the prioritized request, bandwidth is allocated to each Optical Network Unit (ONU). The paper addresses Inter and Intra ONU allocation. The bandwidth is allocated fairly among the ONUs. The proposed algorithm is evaluated against various dynamic bandwidth allocation algorithms on different performance characteristics like fairness, bandwidth utilization and packet delay using MATLAB. Findings: The simulated results of the proposed algorithm show improvements in performance characteristics compared to the other algorithms.

Keywords

Bandwidth Utilization, Dynamic Bandwidth Allocation (DBA), EPON, Fairness, User Prioritization

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Surbhi Jain ¹, A. Brintha Therese ¹

Affiliations
1 School of Electronics Engineering Department, VIT University, Chennai-600127, IN

Abstract

The optical networks are fast, robust and error-free, but there are some nonlinearity hindrances which prevent them from being a perfect medium. The performance of wavelength division multiplexing (WDM) in radio over fiber (RoF) systems is found to be intensely influenced by nonlinearity characteristics within the fiber. In this paper, the performance of WDM network is analyzed using optical filter and various external modulation schemes under FWM nonlinearity effect. Here, the effect of input signal power on FWM is studied. Also, the threshold value of input power for different external modulation technique is calculated and hence duobinary modulation is found to be optimal technique for reducing FWM effect in WDM networks.

Keywords

DPSK, Duobinary, Four Wave Mixing (FWM), Noise Power, QAM, QPSK, Radio over Fiber (RoF), SNR, Wavelength Division Multiplexing (WDM).

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Surbhi Jain ¹, A. Brintha Therese ²

Affiliations
1 Vellore Institute of Technology, Chennai, IN
2 SENSE Department, Vellore Institute of Technology, Chennai, IN

Abstract

The optical networks are fast and error free but due to some nonlinearity effects, its performance degrades. The performance of wavelength division multiplexing (WDM) in radio over fiber (RoF) systems is found to be strongly influenced by nonlinearity characteristics inside the fiber. In this paper, we have studied the effect of four wave mixing (FWM) as one of the influential factors in the WDM for RoF using Optisystem Software.

Keywords

Radio Over Fiber (ROF), Wavelength Division Multiplexing (WDM), Channel Spacing, Power Level, Nonlinearities, Four Wave Mixing (FWM).

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