Amplitude and phase noise of periodic orbits in a nonlinear optical system: theory and experiments

In this paper we present results of amplitude and phase noise analysis and measurements of periodic orbits and relate them to signal-to-noise ratios of subcarrier communication systems. The nonlinear system that we have chosen to investigate is the two-section Fabry-Perot laser diode, which supports self-sustained pulsation dynamics. Theoretical analysis is based on the rate equations with Langevin noise forces with self-consistent auto- and cross-correlation functions. The dynamics with noise is obtained by numerical integration using the fourth-order Runge-Kutta method. The phase and amplitude noise is then obtained using digital filtering and spectral analysis. The noise characteristics are also derived analytically using a perturbation method. Experimentally, the noise characteristics of the periodic orbit are analyzed in the electrical domain after photodetection. With proper bandpass filtering, the amplitude and phase noise of each harmonic in the periodic orbit is characterized independently