In-line saturable absorber in transmission systems with cascaded semiconductor optical amplifiers

A significant improvement of high bit-rate RZ transmission system performance was demonstrated by employing an in-line saturable absorber. The basic features of such a system are discussed. Error free 5-Gb/s single channel transmission over 30000 km has been obtained at 1.3-μm in a fiber loop setup. The saturable absorber was fabricated directly in the semiconductor optical amplifier by ion-implantation.