New M.E. Thesis Submitted from ECE Student


The tremendous growth of Internet traffic has created increasing demand on high capacity optical communications networks. The optical transmission networks offer improved possibilities for dealing with ever growing demands on transmission bandwidth and system capacity. In the last 20 years, the optical transmission networks have become one of the most important part in the telecommunication hierarchy, whose seamless integration with conventional network applications and services forces a further development and a broader deployment of optical networks in all telecommunication areas.

The deployment of future optical networks and upgrade of existing ones will be governed by the growth of the traffic in all network areas. The question arising here is, what is the best transmission technology to be implemented in future systems. Dense wavelength division multiplexing (DWDM) networks has emerged as a very attractive option. Choice of modulation format plays a critical role in the design and performance of fiber optic communication system. In the next generation of lightwave systems, high speed data rate like 10Gb/s or 40Gb/s is very attractive. In addition, to pack more channels into one single fiber, channel spacing is decreased from 200GHz to 50GHz. The direct side-effect is that linear and nonlinear degrading effects will be severe in such high-speed lightwave systems. An optimal modulation format which is more tolerant to linear and nonlinear impairments is needed urgently. Using the different types of modulation formats, it is predicted that the advanced modulation formats enhance the overall performance of the optical communication systems at high bit rate In this thesis, focus of work is set on 4 x 10Gb/s based DWDM optical transmission system with different modulation formats in order to investigate the role of modulation formats in implementation of next generation optical transmission networks. In this, we studied different components of DWDM transmission system and its configuration. DWDM system is limited by different linear and nonlinear impairments. Linear impairments include optical attenuation, chromatic dispersion and polarization mode dispersion. Nonlinear impairments include Kerr nonlinearities and scattering.
In the first stage I designed and investigated single-channel Transmission System at 10 Gb/s channel data rate and then 4 channel DWDM system(4 x 10Gb/s) is designed and variation in the results with different modulation formats are studied. I generated and studied the characteristics of modulation formats like Return to Zero and advanced modulation formats like CSRZ and SSBRZ. All these modulation formats Performance is compared in single channel. Different results such as optical spectrum, electrical spectrum, eye-diagram, Q-Value, eye opening, eye-closure, OSNR etc. are observed to evaluate the performance of the system. Finally the performance of four channel DWDM system at 4 x 10Gb/s data rate with RZ, CSRZ and SSBRZ modulations formats has been analyzed.

Leisure Readings :