This thesis studies and examines the behaviors and characteristics of various kinds of fiber ring lasers, which includes active mode-locked erbium doped fiber ring laser, parametric amplifier based fiber ring laser, nonlinear optical loop mirror (NOLM) – nonlinear amplifying loop mirror (NOLM-NALM) fiber ring laser and some of their regenerative counterparts for better stability. Ultrafast operations: 40GHz to Tera-Hertz optical pulses have been achieved by using either fractional temporal Talbot effect or rational harmonic detuning with Gaussian modulating signal. Gaussian modulating signal is studied and used in replace of cosinusoidal modulating signal for AM mode-locking. With this type of modulating signal, a record high rational harmonic detuning order has been achieved in the active harmonically mode-locked fiber ring laser: 1230th order, with a base modulation frequency of 100 MHz. Phase plane analysis is used to study the laser system stability, which shows transient and steady state behaviors of the system. Bidirectional lightwaves propagation behaviors in an erbium doped fiber ring laser are investigated and NOLM-NALM structure is proposed. Three operation regimes are obtained numerically, namely single operation, period doubling operation and chaotic operation; however only two are observed experimentally due to hardware limitations.