Overview of the Key Advantages of OFDM System and its Effects of Drawbacks

Due to increasing data traffic worldwide, the demands on optical communication systems in terms of bit rate, spectral efficiency and bandwidth flexibility will increase in the coming years. To cope with this, among other things, the multi-carrier orthogonal frequency division multiplexing (OFDM) in combination with coherent reception is under discussion for future systems. However, as OFDMS systems are sensitive to nonlinear perturbations, this work presents Procedures that reduce such influences. Thus, impairments of the channel estimation are examined by transmitter-side quantization errors and possibilities are shown of reducing them or even eliminating them altogether. In addition, the influence of the non-linear characteristic of the electro-optical modulator is studied and demonstrated that nonlinear distortions can be significantly reduced by digital preprocessing of the transmission signal. On the receiver side, this work deals with synchronization procedures for frame detection and estimation of the frequency deviation between carrier and local oscillator. For this purpose, digital methods are developed which provide a sufficiently accurate estimate for modulation formats with high spectral efficiency under the influence of chromatic dispersion and amplifier and phase noise.