We propose new frequency-modulation optical-optical triple-resonance (
FM-OOTR) optical heterodyne spectroscopy, which can eliminate the Dopp
ler-background in the recently developed optical-optical triple-resona
nce (OOTR) spectroscopy and provide improved resolution and sensitivit
y. Theoretical considerations and line shape calculations are presente
d. The potential applications of FM-OOTR technique to laser frequency
stabilization with significant advantages can be expected.