The amplitude noise responses of optical-frequency-discriminating systems,
based on Fabry-Perot cavities with intensity noise compensation, are analyz
ed considering also the effect of the resonator transient. From the point o
f view of amplitude noise immunity, systems based on transmission or reflec
tion alone behave in a quite similar way within the discriminator bandwidth
, whereas a proper combination of both these signals not only increases the
sensitivity to frequency noise but also allows for higher rejection to amp
litude noise.