We present a method by which the effect of laser field variations on the si
gnal output of an interferometric gravitational wave detector is rigorously
determined. Using the Laser Interferometer Gravitational Wave Observatory
(LIGO) optical configuration of a power recycled Michelson interferometer w
ith Fabry-Perot arm cavities as an example, we calculate the excess noise a
fter the input filter cavity (mode cleaner) and the dependence of the detec
tor strain sensitivity on laser frequency and amplitude noise, radio freque
ncy oscillator noise, and scattered-light phase noise. We find that noise o
n the radio frequency sidebands generally limits the detector's sensitivity
. (C) 2000 Optical Society of America [S0740-3232(00)01401-0].