Optical Communications

Aim of the course Optical Communications is providing the tools to design and realize high performance optical systems and networks. It describes both advanced devices and systems as optical amplifiers, photonic crystals and optical coherent communication systems, and some fundamental phenomena occurring in optical fibre like birefringence and non-linear effects. Finally, the capacity of the optical channel is analysed both in linear and in non-linear regime. It is preparatory to Optical Communications the course Network Infrastructures.

Special Optical Fibres: Plastic Optical Fibres (POF), Photonic Crystals, Photonic crystals optical fibres. Optical Amplifiers: Fundamentals on optical amplification, 3-levels systems; 2-levels systems, Optical Gain. Gain Saturation, Noise in optical amplifiers (ASE, Amplified Spontaneous Emission), EDFA (Erbium Doper Fiber Amplifier), SOA (Semiconductor Optical Amplifier), Distributed optical amplification. RAMAN Amplifier. Birefringence and polarization dispersion: Birefringence, Differential Group Delay, PMD (Polarization Mode Dispersion), Jones matrix, Polarization representation in the Stokes space, Stokes vector and Poincaré sphere, Müller matrix, Principal States of Polarization, PMD Dynamical Equation, PMD statistics, Effects of the PMD on the performance of IM-DD optical communication systems, Measure techniques for PMD, PMF (Polarization Maintaining Fibres). Optical fibre propagation in non-linear regime: Non-linear Schrödinger Equation, SPM (Self-Phase Modulation), FWM (Four-Wave-Mixing), XPM (Cross-Phase Modulation),Solitons. Coherent Optical Communication Systems: Coherent optical systems: homodyne and heterodyne receivers, Demodulation techniques: coherent, differential, envelope, Balanced optical receiver. Phase-quadrature optical receiver. Polarization diversity optical receiver, Phase mo/demodulation techniques (PSK, DPSK), Amplitude mo/demodulation techniques (ASK – envelope demodulation), Frequency mo/demodulation techniques (FSK, CPFSK), Polarization mo/demodulation techniques (PolSK, ASPSK), Multilevel coherent optical systems (M-PSK, QPSK, QAM, N-SPSK, N-4QSK). Capacity of the optical fibre communication channel: Capacity of the optical channel in linear regime, Capacity of the optical channel in non-linear regime.

Silvello Betti