This is the lowest 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 lowest received power seen in the interval is what matters most for this metric, since a dip toward the receiver's sensitivity floor is the earliest warning of an impending loss-of-signal condition. For example, if inOpticalPowerMin dips close to the receiver's specified sensitivity threshold during just one interval each night, an admin might correlate that with a nightly temperature swing affecting a marginal splice.