In recent years, optical fibers became increasingly important means for huge amount of data transport. As time goes on, data dimensions requested become higher and higher, and deployment of submarine links based on optical fibers cables has spread out in all the world. Most recent systems use coherent technology in order to satisfy such data requests due to the fact that coherent transceiver exploits power, phase and polarization modulation. But there exist submarine cables deployed in the past that used to work with older, IMDD (Intensity-Modulation Direct-Detection) technology, in which only power modulation was used to carry information. The peculiarity of these links is that chromatic dispersion is compensated periodically along the fiber spans (Dispersion Managed, DM), by placing Dispersion Compensation Units (DCU).