Study On Chaotic Characteristics Of Polarization-maintaining Erbium-doped Fiber Ring Laser

The polarization-maintaining erbium-doped fiber ring laser which was based on the structure of saturable absorber can output stable ultra-narrow line-width single frequency laser, and has been applied in the optical fiber sensing and communication system, however, the laser’s characteristic in the field of non-linear dynamics research has not been studied properly. Under the condition of increasing degrees of freedom, the laser’s time domain output characteristic changing with laser parameters has not been analysised theoretically and experimentally.In this paper, the polarization-maintaining erbium-doped fiber ring laser’s characteristic of output which under the condition of pump modulation, loss modulation and external feedback has been studied by simulation and experimental methods. And the output time series have been analysised by chaos detecting methods. The main research content is as follows:1. For pump modulation, numerical and experimental results both show that the laser will be driven into chaotic state by a three-period-paroxysmal or a period-doubling bifurcation.2. The characteristic of laser’s output under the condition of loss modulation has been analysised theoretically. Loss modulation has been introduced by cavity length modulation, and the laser in the state close to the threshold has driven into chaotic state by paroxysmal route with increasing of modulation frequency. Another kind of loss modulation is introduced by intra-cavity polarization-maintaining fiber M-Z Interferometer and experiment shows that the laser enters chaotic state by paroxysmal route or period-doubling bifurcation.3. The effect of feedback caused by 40 km delay fiber has been studied numerically and experimentally. The theory appeared that the laser entered chaos through period-doubling bifurcation. While in the experiment, the one-dimensional intensity chaos was not observed. However, the laser lost its stability by the microwatt level optical feedback, and entered the multimode coherence-collapse state.The paper has studied the nonlinear dynamics characteristic of polarization-maintaining erbium-doped fiber ring laser theoretically and experimentally. The condition to produce chaos and the unstable factor were griped, which could expand the area of chaotic fiber laser’s application and made the foundation of advancing the stability of fiber ring laser.