In both cases the same amount of light energy is launched. However, because light detectors are sensitive to light power, the shorter light pulse will appear to be one million times brighter and will therefore be easier to detect. This peak power sensitivity concept of light processing is a very important concept and is often neglected in many optical communications systems published in various magazines. TOP Misc Stuff Independent on how long the light remains on. The watt is more convenient to use since light detectors, used to convert the light energy into electrical energy, produce an electrical current proportional to the light power, not its energy.
Detectors often have conversion factors listed in amps per watt of light shining on the detector.
Remember, energy is power multiplied by time.