Since the advent of optical communications, a greattechnological effort has been devoted to the exploitation of the huge bandwidth of optical fibers. Sta- ing from a few Mb/s single channel systems, a fast and constant technological development has led to the actual 10 Gb/s per channel dense wavelength - vision multiplexing (DWDM) systems, with dozens of channels on a single fiber. Transmitters and receivers are now ready for 40 Gb/s, whereas hundreds of channels can be simultaneously amplified by optical amplifiers. Nevertheless, despite such a pace in technological progress, optical c- munications are still in a primitive stage if compared, for instance, to radio communications: the widely spread on-off keying (OOK) modulation format is equivalent to the rough amplitude modulation (AM) format, whereas the DWDM technique is nothing more than the optical version of the frequency - vision multiplexing (FDM) technique. Moreover, adaptive equalization, ch- nel coding or maximum likelihood detection are still considered something ¿exotic¿ in the optical world. This is mainly due to the favourable char- teristics of the fiber optic channel (large bandwidth, low attenuation, channel stability, ...), which so far allowed us to use very simple transmission and detection techniques.

Comprises the proceedings of the 2004 International Tyrrhenian Workshop on Digital Communications, which will be held in Italy in 2004

Solving the Nonlinear Schrödinger Equation.- Modulation and Detection Techniques for DWDW Systems.- Best Optical Filtering for Duobinary Transmission.- Theoretical Limits for the Dispersion Limited Optical Channel.- Capacity Bounds for Mimo Poisson Channels with Inter-symbol interference.- QSpace Project: Quantum Cryptography in Space.- Quantum-aided Classical Cryptography with a Moving Target.- Channel Coding for Optical Communications.- Soft Decoding in Optical Systems: Turbo Product Codes vs. LDPC Codes.- Iterative Decoding and Error Code Correction Method in Holographic Data Storage.- Performance of Optical Time-spread CDMA/PPM with Multiple Access and Multipath Interference.- Performance Analysis and Comparison of Trellis-coded and Turbo-coded Optical CDMA Systems.- A Methodology for Calculating Performance in an Optical Fiber Communications System.- Markov Chain Monte Carlo Technique for Outage Probability Evaluation in PMD-compensated Systems.- A Parametric Gain Approach to Performance Evaluation of DPSK/DQPSK Systems with Nonlinear Phase Noise.- Characterization of Intrachannel Nonlinear Distortion in Ultra-high Bit-rate Transmission Systems.- Mathematical and Experimental Analysis of Interferometric Crosstalk Noise Incorporating Chirp Effect in Directly Modulated Systems.- On the Impact of MPI in All-Raman Dispersion-compensated IMDD and DPSK Links.- Modulation Formats for Optical Fiber Transmission.- Dispersion Limitations in Optical Systems Using Offset DPSK Modulation.- Integrated Optical Fir-filters for Adaptive Equalization of Fiber Channel Impairments at 40 Gbit/s.- Performance of Electronic Equalization Applied to Innovative Transmission Techniques.- Performance Bounds of MLSE in Intensity Modulated Fiber Optic Links.- On MLSE Reception of ChromaticDispersion Tolerant Modulation Schemes.