Transparent All-Optical Regeneration and Wavelength Conversion in Dense Wavelength Division Multiplexing (DWDM) transmission systems are key issues to ensure the progress of the transparent networks and their actual implementation. In this paper recent progress of several All Optical 2R experimental systems focused on single and Multi-channel approaches will be reported. In particular will be analysed the implementation matters and the regeneration capabilities of several devices based on the exploitation of non-linear phenomena in several media: Semiconductor Optical Amplifier (SOA) and Optical Fibres in non linear regimes
