Pulse width ( ton ) and dark period ( toff ) combine to yield more common paramteres - Frequency and Duty Cycle - which, combined with peak power ( Pp ), can be used to calculate average power ( Pa ).
DC=ton+toffton=PpPa
Careful, though: these parameters alone can be misleading, as different combinations can lead to the same (a, c, and d) or different (b and c or d) average outputs.