Fig. 1. Schematic diagram of the stochastic resonance system.

Fig. 2. Optical bistable hysteresis in the SOA with α=20  cm−1, η=0.75, g0=280  cm−1, L=300  μm, b=2, φ0=π4, and R=0.3.

Fig. 3. Bistable output characteristics with different system parameters of the SOA: (a) b=3, φ0=π4, R=0.3, and L=100  μm (red), 200 μm (green), 300 μm (blue), and 400 μm (black); (b) L=300  μm, b=3, φ0=π4, and R=0.1 (red), 0.2 (green), 0.3 (blue), and 0.4 (black).

Fig. 4. Bistability characteristics with different parameters: (a) R=0.3, L=300  μm, b=3, and φ0=0 (red), π4 (green), π3 (blue), and π2 (black); (b) R=0.3, L=300  μm, φ0=π4, and b=1.5 (red), 2 (green), 3 (blue), and 4 (black).

Fig. 5. Transmission properties of the stochastic resonance system with increasing noise intensities. (a)–(d) input signals S0=0.5  MW/cm2 with noise, in which normalized noise intensities D are 0∶1, 1∶1, 5∶1, and 10∶1, respectively; (a′)–(d′) the corresponding output signals through the stochastic resonance system with parameters L=300  μm, R=0.3, φ0=π4, and b=3.

Fig. 6. (a) Cross-correlation coefficients and (b) the cross-correlation gain as functions of the normalized noise intensity D at system parameters L=300  μm, R=0.3, φ0=π4, and b=3. The solid curves are the optimal fitted curves neglecting the random fluctuation.