Constraint Based Quality Estimation and Performance Analysis in WDM/DWDM Network

Abstract

The rapid growth of internet with high speed applications such as online video and multimedia conferences require larger bandwidth. The present wireless or wired network is not capable enough to handle such high-speed data communication. It can be managed with the proper management of Wavelength Division Multiplexing/Dense Wavelength Division Multiplexing (WDM/DWDM) technology, which uses optical fiber as its transmission medium known as lightpath where data is transmitted in the form of a light signal. The implementation of WDM/DWDM technology is a two step approach, where the first step is lightpath provisioning and the second step is Wavelength Assignment (WA). The combination is termed as Routing and Wavelength Assignment (RWA) technique, which is the fundamental aspect of WDM/DWDM optical network system. RWA plays a key role to provide a Quality of Transmission (QoT) to the end users. It depends on various Physical Layer Impairments (PLIs), which affects QoT in optical networking.
This research work focuses on the estimation and management of PLIs based quality parameters in WDM/DWDM networks in order to get efficient and qualitative optimal lightpath for the end users. PLIs such as Dispersion Penalty (DP), Stimulated Raman Scattering (SRS), Amplified Spontaneous Emission (ASE), and Four-Wave Mixing (FWM) etc., are considered for the estimation of quality parameters to achieve better QoT with maintaining of minimum Blocking Probability (BP). Based on these, four different approaches of estimation techniques are listed below:
optical fiber can accommodate multiple channels of different wavelength over the single transmission medium. Also, refractive index of the fiber is the function of wavelength, and hence different wavelengths lead to different speeds of signal. As a result, the light pulse gets broaden, which is known as dispersion. This approach estimates the DP over the lightpath. Based on DP, optical lightpath is computed among all possible path along with the analysis of blocking probability.
• Optical amplifiers are used to enhance the signal strength in WDM/DWDM network. These amplifiers also lead to SRS. In order to mitigate the crosstalk arising from to SRS, an algorithm has been suggested to compute power penalty parameter for all possible paths. The variation in power penalty with a changing input power of the signal is investigated to determine path selection.
• The power penalty due to SRS can be eliminated by using Erbium Doped Fiber Amplifier (EDFA) in place of Raman amplifier. But the EDFA generates ASE noise, that degrades optical signal strength. It is represented in terms of Optical Signal-to-Noise Ratio (OSNR), which further uses RWA algorithm to improve the QoT of a lightpath.
• Based on PLI information along with RWA, Ant Colony Optimization (ACO) has been used in order to acheive a better QoT over a lightpath. The ACO based RWA (ACO-RWA) has been compared with traditional ACO. In summary, the objective of the thesis is to provide four different approaches of quality parameter estimation in order to provide a better QoT over a lightpath.algorithm, and found to be superior in performance.