Unbalance of the Sagnac interferometer through nonlinear asymmetry

In this work, we studied the behavior of Sagnac interferometer powered by a CW signal and under the nonlinear effects of self-phase modulation, cross-phase modulation, and Raman, in two configurations (balanced and unbalanced) and five scenarios (by varying the value of the Raman fraction). In the balanced configuration, we observed that the presence of Raman effect in the loop changes the curves of transmissivity and reflectivity of the device, but only the components generated by the Raman effect (Stokes waves) are switched to the transmitted port. In the unbalanced configuration, we obtained an oscillating behavior as for transmissivity and reflectivity, which breaks the characteristic of nonlinear fiber mirror, thus enabling the transmission of the pumping wave for certain combinations of values of input power and Raman fraction.