Mode locked fiber ring laser using graphene nanoparticles as saturable absorbers to compress the pulse width has been studied. An experimental method to demonstrate the generation of pulse train with 50 GHz repetition rate with an ultrashort pulse width has been demonstrated. This method uses a combination of rational harmonic mode-locking (RHML) and a saturable absorber in the fiber ring laser. The pulse width using saturable absorbers is shorter by about a factor of 2 compared to that without a saturable absorber. Pulse generation using fiber ring laser with a saturable absorber has been analyzed. The experimental results are in agreement with the results from the simulation.