Wavelength monitoring with mutually modulated cross-gain modulation in a semiconductor optical amplifier and Brillouin amplifier

We analyze and implement mutually modulated cross-gain modulation (MMXGM) in a semiconductor optical amplifier (SOA). In this effect, optical wavelength changes are converted into modulation phase changes with high sensitivity and resolution. In the slow-light transition regime, we demonstrate picometer sensitivity to the optical wavelength. We analyze the spectroscopic performance of the SOA-based MMXGM and the previously developed Brillouin-based MMXGM techniques, and compare them to that of material-dispersion-enhanced, slow-light spectroscopy in a Brillouin amplifier.