Fig. 1. Structure of the proposed laser ring. CIR, optical circulator; OC, optical coupler; OI, optical isolator; VA, variable attenuator.

Fig. 2. Bifurcation diagrams for (a) the proposed laser ring with T1=0.7  ns, T2=1  ns, T3=1.3  ns, Δf1=Δf2=0  GHz, and k2=0  ns−1, and (b) the ECSL subject to COF.

Fig. 3. ACF (the first and second columns) and DMI (the third and fourth columns) computed from the intensity and phase time-series of chaos in different systems, respectively. The first row is for the ECSL with COF (kf=20  ns−1, τf=3  ns), the second row is for the laser ring without a feedback loop in SL2, the third row is for the laser ring with a moderate feedback loop in SL2 (k2=30  ns−1, τ2=2  ns), and the fourth row is for a feedback strength enhanced case (k2=60  ns−1). Parameters for the injection in the laser ring are set as σ1=σ2=σ3=20  ns−1, T1=0.7  ns, T2=1  ns, T3=1.3  ns, and Δf1=Δf2=0  GHz.

Fig. 4. TDS size as a function of the injection strengths and feedback strength in SL2. (a) and (b) present the TDS observed by the ACF from the intensity and phase time-series, respectively, and (c) and (d) show the TDS identified by the DMI from the intensity and phase time-series, respectively; Δf1=Δf2=0  GHz.

Fig. 5. TDS size as a function of the feedback strength and time delay in SL2 with σ1=σ2=σ3=20  ns−1 and Δf1=Δf2=0  GHz. (a) and (b) present the TDS observed by the ACF from the intensity and phase time-series, respectively, and (c) and (d) show the TDS identified by the DMI from the intensity and phase time-series, respectively.

Fig. 6. Evolution of the TDS size in the detuning frequency space with σ1=σ2=σ3=20  ns−1, and k2=30  ns−1. (a) and (b) present the TDS observed by the ACF from the intensity and phase time-series, respectively, and (c) and (d) show the TDS identified by the DMI from the intensity and phase time-series, respectively.