Study and Analysis of Spectrally Efficient Modulation Formats in High Speed DWDM Optical Systems

Abstract

The exponentially increasing demand for the channel capacity in long haul high speed transmission systems has pushed the fiber-optic communication technology to adopt dense wavelength division multiplexing (DWDM) system as a viable solution. To maximize the performance of such optical networks, suitable system design strategies to optimize the parameters related to data transmission within the channel characteristics becomes a critical area of research. Usually the optical channel capacity is influenced by signal shape, dispersive and non-linear characteristics of the guiding medium and the interference from various sources. These impairments appear to be much detrimental in a multi-channel optical guiding medium especially at a higher data rate in the presence of fiber nonlinearities. Thus, in order to exploit the best system transmission capacity with the least performance degradation, a thorough understanding, modeling and characterization of optical channel behavior under various operating environments becomes an important problem. newlineThe main objective of this thesis is to analyze different approaches to mitigate the channel impairments influencing the capacity limitations in optical fiber communication. Changes in optical transmitters, receivers and transmission medium are not a preferred solution owing to relatively higher cost and complex hardware setup requirements. However, efficient optical modulation approach emerges as a promising technique with cost effective solution in the current scenario. In fact, signal spectral bandwidth, tolerance to dispersion, resistance to nonlinear crosstalk, susceptibility to accumulated noise, and other system performance measures are directly related to the optical modulation format. Incorporation of certain modulation scheme in optical transmitter with appropriate receiver helps to improve the capacity crisis of the transmission system quite effectively. Recent research in advanced optical modulation formats confirms the improved data transmission with an acceptable syst