Analysis of the nonlinear optical switching in a Sagnac interferometer with non-instantaneous Kerr effect

作者：Ferreira A C; Costa M B C; Coelho A G Jr; Sobrinho C S; Lima J L S; Menezes J W M; Lyra M L; Sombra A S B^*

来源：Optics Communications, 2012, 285(6): 1408-1417.

DOI：10.1016/j.optcom.2011.10.026

• Sagnac interferometer
• NOLM
• Relaxed Kerr nonlinearity
• Soliton
• Quasi-soliton
• All-optical signal processing

In this work we present a study of the performance of nonlinear switching in a Sagnac interferometer under the action of a relaxed Kerr nonlinearity, using ultrashort optical pulses. Soliton and quasi-soliton pulses have been used as initial conditions. We include the effect of GVD (Group Velocity Dispersion) and consider that losses are negligible. The transmission, compression factor (C) and extinction ratio [X-Ratio(tr)] curves versus input energy were analyzed for two lengths of the loop (1Z(o) and 2Z(o)) of the Sagnac interferometer, where 4 is one soliton period. It was verified that an increase of the response time (tau) of the relaxed Kerr nonlinearity leads to a degradation of the nonlinear switching, transmission, compression factor and extinction ratio curves. For instance, in the quasi-soliton propagation regime with loop of length 1Z(o) and input energy 1.83 pJ, the extinction ratio (X-Ratio(tr)) decreases from +8.13 dB, at the instantaneous nonlinear medium, to -0.83 dB, -2.50 dB, -5.95 dB, -8.63 dB, -10.11 dB and -12.10 dB, at the relaxed medium with tau=1 ps, tau=2 ps, tau=5 ps, for tau=10 ps, tau=15 ps and tau=30 ps, respectively. In the soliton propagation regime with loop of length 2Z(o) and time duration of 10 ps, for the input pulse (pump power of 0.34 W), one can observe that for the non-instantaneous nonlinear medium, as tau increases, the transmitted output pulses are delayed to longer times (21.49 ps, 23.9 ps and 25 ps) and the pulse envelope starts presenting broadening effects (14.7 Ps and 29 ps) for tau=2 Ps and 5 ps, respectively. In our analysis, for the Sagnac interferometer with ring of length 2Zo=5.06 km, the chirp distribution has revealed that the spectral profile of the output pulses are smoother for the non-instantaneous medium with tau=2 ps and 5 ps. In this sense, these two last situations are more suitable for switching applications in WDM systems. These studies are crucial for the analysis of the behavior of the Sagnac interferometers based in non-instantaneous Kerr response fibers, applied in telecommunication systems, in optical signal processing, optoelectronics instrumentation and in several related fields.

• 出版日期2012-3-15