Correlation properties and power density spectrum of shot noise process; Laser phase noise modeling and Lorentzian power spectrum of lasers; Coherent optical communication systems: Homodyne and heterodyne detection schemes, BER analyses - super - quantum and shot noise limits for homodyne PSK, Synchronous and asynchronous FSK, Impact of finite laser linewidth on BER, Polarization control and diversity schemes, Frequency alignment schemes; Review of optical amplifiers - Semiconductor amplifiers, Erbium - doped f ibre amplifiers (EDFAs) and Raman amplifiers, Analytical modelling of gain saturation in EDFAs, Gain equalization in EDFAs, ASE noise in EDFAs, Amplifier cascades, Amplifier spacing penalty; BER analysis of lightpaths in WDM backbones in presence of ASE no ise and switch crosstalks; Optical duobinary modulation: Spectral efficiency, Basic scheme, BER analysis, Impact of fibre nonlinearities; Advanced modulation schemes, Advanced detection schemes, Advanced Coding Schemes, Advanced optical networking, Optical Channel capacity and energy efficiency.