Network Infrastructures

The aim of the course is to provide basic knowledge in the telecommunication network infrastructures, especially in those systems based on wired connection, both in the access network and in the transportation one.

1. Copper transmission; Twisted pairs; attenuation; crosstalk effects NEXT (Near-End-X-Talk), FEXT (Far-End-X-Talk); Vectoring. 2. x-DSL Systems (x-Digital Subscriber Line) ADSL, SDSL, HDSL, SHDSL, VDSL. Modulation techniques (DMT-Digital Multi Tone; OFDM-Orthogonal Frequency Division Multiplexing). 3. Optical Fibre Systems I Introduction II Optical Fibres II.1 Light reflection and refraction. II.2 Optical fibres: description by geometric optics methods (core, cladding, step-index fibre; graded-index fibre). II.3 Maxwell’s Equations. II.4 Optical fibre propagation modes (cut-off). II.5 Single-mode optical fibres (HE11, mode-field diameter). II.6 Attenuation (attenuation coefficient, material absorption, Rayleigh scattering). II.7 Chromatic dispersion (group velocity dispersion, material dispersion, guide dispersion, higher-order dispersion, optimization of the refractive index profile in optical fibre core). II.8 Polarization effects in optical fibres (birefringence, polarization state fluctuations, Jones formalism representation, Stokes parameters representation, polarization dispersion). II.9 Linear regime propagation equation (gaussian pulses, chirped gaussian pulses, optical fibre “bandwidth”). III Light-matter interaction III.1 Wave-particle light characteristics. III.2 Energy and momentum conservation. III.3 Semiconductor energy band structure. III.4 Absorption. III.5 Spontaneous emission. III.6 Stimulated emission. IV Semiconductor Laser IV.1 Optical Gain IV.2 Feedback and threshold conditions. IV.3 Rate equations. IV.4 Semiconductor laser structures. IV.5 Multimode operation regime. IV.6 Single-mode operation regime (DFB, DBR). IV.7 CW operation: optical power-current response. IV.8 Semiconductor laser modulation: “small” signal regime, “large” signal regime (clipping), frequency response, chirping. IV.9 Noise in semiconductor laser (RIN, phase noise). V Passive optical devices V.1 2×2 directional coupler. V.2 Coupled mode theory. Coupling equations. V.3 Star coupler. V.4 Phase Array based devices (AWG). V.5 Optical filters (Fabry-Perot, grating). Tunable optical filters. V.6 Optical isolators. VI Integrated optics devices VI.1 Linear electro-optic effect (Pockels effect). VI.2 Amplitude and phase electro-optic modulators (LiNbO3). VI.3 Electro-optic switch. VII Optical amplifiers VII.1 Optical amplification. VII.2 EDFA, Erbium Doper Fiber Amplifier: amplification, pump techniques, EDFA architectures, gain characteristics, optical power conversion efficiency, noise (ASE, Amplified Spontaneous Emission), system applications (booster, in-line amplifier, pre-amplifier). VII.3 Raman distributed amplifier. VIII Optical receivers VIII.1 Photodiodes: PIN, APD, quantum efficiency, responsivity, shot-noise, bandwidth. VIII.2 Direct Detection (DD) receiver structure: front-end amplifier (transimpedence amplifier, high impedence amplifier). VIII.3 Pre-amplifier based optical receiver. VIII.4 Optical detection quantum limit. VIII.5 Optical receiver performance: thermal noise, sensitivity, signal-to-noise ratio (S/N), Bit-Error-Rate (BER). IX Point-to-point digital optical systems IX.1 Link power budget. IX.2 Dispersion effects: penalty, bandwidth limitations. IX.3 Long-haul in-line amplifiers optical systems. IX.4 NRZ, RZ formats. IX.5 Dispersion compensation. X Multi-channel optical systems X.1 TDM (Time Division Multiplexing) optical systems. X.2 SCM (Sub-Carrier Multiplexing) optical systems. X.3 WDM (Wavelength-Division-Multiplexing) optical systems: wavelengths ITU grid, tunable optical sources, crosstalk effects. XI Nonlinear optical effects. XI.1 Stimulated Brillouin scattering. XI.2 Stimulated Raman scattering. XI.3 Kerr effect: Self-Phase Modulation (SPM), Cross-Phase Modulation (XPM), Four-Wave Mixing (FWM). XII Optical network topologies. XII.1 PON (Passive Optical Network). XII.2 Optical access networks: FTTC, FTTB, FTTH, WDM+PON architectures. XII.3 Optical Transport Network. ADM (Add and Drop Multiplexer). OXC (Optical Cross Connect). All Optical Networks. XIII Measure techniques for optical fibre communication systems: attenuation, OTDR; chromatic dispersion measures, measures in PON networks.

Silvello Betti