Comparison of fiber-based Sagnac interferometers for self-switching of optical pulses

Self-switching of ultrashort optical pulses in a gain-distributed nonlinear amplifying fiber loop mirror (NALM) is investigated numerically in the soliton regime. Switching characteristics of this device is compared to those of the nonlinear optical loop mirror (NOLM) and the conventional NALM that uses a lumped gain. We show that, as compared with the NOLM or the conventional NALM, the gain-distributed NALM can produce higher-quality pulses and permits more efficient pulse compression. We also show that the gain-distributed NALM has several advantages over the conventional NALM such as sharpened switching edges, flattened switching peak, and robustness to gain variations.