This is the highest value recorded during the current performance-monitoring interval of the received optical power level measured at this port's input during the current performance-monitoring interval, expressed in the device's optical-power units. The highest received power seen in the interval matters because too strong a signal can saturate a receiver just as too weak a signal can starve it, so this checks against the upper end of the operating range. For example, after replacing a long attenuated span with a shorter fiber run, an admin would check that inOpticalPowerMax hasn't risen high enough to overdrive the receiver and require adding an attenuator.