In this thesis, we propose a fiber ring harmonic mode-locked fiber laser and detuning modulation frequency. We generate amplitude modulation by exciting outside RF modulation signal. In case of producing high speed pulse train signal, we also drive isolator in the fiber ring cavity system to stable the RMS jitter. Then we also generate phase modulation by exciting outside RF signal to make the phase longitudinal modes locking. At the last, we utilize amplitude modulation and phase modulation to produce high speed pulse train in the fiber ring cavity system. In this fiber ring cavity system, we use three different kinds component to produce high speed pulse train and detuning the RF modulation frequency to ameliorate RMS jitter.