Single mode fiber optic transmissions and communications technologies are constantly growing and facing more challenges that limited its ability to transmit for long distances with great capacity (e.g.10Gbps and 40Gbps). One of these challenges is the degradation phenomenon that occurs when the optical signal passing through the fiber. There are three causes of this degradation, power attenuation, dispersion and nonlinear effects. Minimization of these effects will help the system to support long haul transmission distance with high capacity. In this paper, an optical communication link is constructed using Optisystem7.0. The degradation effect is studied and analyzed based on the BER and Eye Diagram obtained at the speed of 10 G bps and a distance ranging between 60 km to 100 km. The results show that the optical signal degrades when the transmission distance exceeds 60 km. An optical amplifier is introduced to eliminate the attenuation effect on the transmitted signal. It is found that at the speed of 40 Gbps the system performance limited to a distance of 5 km and this is due to the high dispersion effect. The results also show that Chromatic dispersion is the most significant affect of degradation phenomenon. The absence of nonlinear effect is also observed when the transmission power in the range of 1mw to 15mw.