MULTIPLEXED DIODE-LASER SENSOR SYSTEM FOR SIMULTANEOUS H2O, O-2, AND TEMPERATURE-MEASUREMENTS

A multiplexed diode-laser sensor system has been developed to monitor multiple species and measure multiple flowfield parameters along a sin gle path with optical fibers and scanned-laser absorption techniques. Two InGaAsP lasers were tuned over H2O transitions near 1347 and 1392 nm, and an AlGaAs laser was tuned over an O-2 transition near 760.65 n m to record fully resolved absorption concurrently at a repetition rat e of 2 kHz. The system was applied to measure H2O, O-2, and temperatur e simultaneously in a heated static cell and in room air. Wavelength m odulation with second-harmonic detection, applied simultaneously in th e O-2 measurements, yielded a minimum detectable absorbance of 1.6 x 1 0(-6)/Hz(1/2) and an O-2 detectivity of 6.3 parts in 10(6) in a 1-m pa th length.