The purpose of this book is to study the transmitting of the optical signal (laser) via optical fibers to reach long distances about 600km and find suitable solutions to fix the problems of attenuation and dispersion and possibility of using optical regenerators which were used as an alternative to traditional ways (electronic regenerators) and showing the benefits of using optical regenerators. Virtual photonics programs have been used to find simulation to optical systems in order to represent special modules for research A dense wavelength division multiplexing was described, whereas 64 channels have been amplified at the same time and was obtain (constant signal output) without going to use automatic gain control. Also a preamplifier module was studied including optical pumping, amplifier length and the effect on gain and noise.