This is the lowest value recorded during the current performance-monitoring interval of the transmitted optical power level measured at this port's output during the current performance-monitoring interval, expressed in the device's optical-power units. The lowest transmit power seen in the interval is the figure that matters most here, since any dip below the transceiver's rated output could be starving the far-end receiver during that period. For example, if outOpticalPowerMin drops noticeably during the hottest part of the day, an admin might suspect the transceiver's laser is thermally derating in a poorly ventilated shelf.