A Nonlinear Model for the Operation of Fiber Optical Parametric Oscillators in the Steady State

In contrast to fiber optical parametric amplification, theoretical studies on the dynamics of fiber optical parametric oscillation are rare. In this letter, we propose a precise nonlinear model to predict the saturation gain and the output power of a fiber optical parametric oscillator (FOPO) in the steady state. This model utilizes the sinusoidal-input describing function as a quasi-linear approximation of the nonlinear dynamics of parametric amplification. To complete the nonlinear model of a FOPO, a model for the linear part of the FOPO cavity is established, and then the block diagram of a FOPO is derived. Based on this block diagram and the related transfer function, a graphical approach to attain the saturation gain and output power is introduced. In addition, a simplified graphical approach and a theoretical upper bound for the output power are investigated. Finally, the proposed model is experimentally verified, in which the theory is in agreement with the experiment.