This is the lowest value recorded during the current performance-monitoring interval of the actual optical carrier frequency measured at this port's input during the current performance-monitoring interval, expressed in MHz. The lowest frequency recorded in the interval helps characterize how far the incoming signal has drifted low, which matters for detecting a laser that's aging toward the edge of its tunable range. For example, an admin tracking a slow laser-aging issue would note that inOpticalFrequencyMin has been drifting further from the target grid frequency release over release.