Optical transmission systems based on standard monomode fibers (SMF) and periodic amplification by means of semiconductor optical amplifiers (SOA) are examined taking into account practical boundary conditions of installed core networks, such as amplifier spacing, fiber attenuation and chromatic dispersion. The performance of ≥10 Gbit/s solution transmission in the second optical window (around λo = 1300 nm) has been investigated numerically. The results show the feasibility of transmission over at least 500 km SMF, even for a system design without signal filtering after the amplification Optimization of the laser transmitter parameters in terms of initial peak power. relative optical phase of neighbouring pulses and mark-to-space ratio leads to a significant improvement of the system capacity and bit error rate and allows a stable operation up to 23 Gbit/s. The capacity and Q-factor can be effectively upgraded using optical bandpass filters.