  Future ground-based gravitational-wave detectors are slated to detect black
hole and neutron star collisions from the entire stellar history of the
universe. To achieve the designed detector sensitivities, frequency noise from
the laser source must be reduced below the level achieved in current Advanced
LIGO detectors. This paper reviews the laser frequency noise suppression scheme
in Advanced LIGO, and quantifies the noise coupling to the gravitational-wave
readout. The laser frequency noise incident on the current Advanced LIGO
detectors is $8 \times 10^{-5}~\mathrm{Hz/\sqrt{Hz}}$ at $1~\mathrm{kHz}$.
Future detectors will require even lower incident frequency noise levels to
ensure this technical noise source does not limit sensitivity. The frequency
noise requirement for a gravitational wave detector with arm lengths of
$40~\mathrm{km}$ is estimated to be $7 \times 10^{-7}~\mathrm{Hz/\sqrt{Hz}}$.
To reach this goal a new frequency noise suppression scheme is proposed,
utilizing two input mode cleaner cavities, and the limits of this scheme are
explored. Using this scheme the frequency noise requirement is met, even in
pessimistic noise coupling scenarios.
