Frequency modulation multiplexing for simultaneous detection of multiple gases by use of wavelength modulation spectroscopy with diode lasers

摘要

Modulation frequency multiplexing provides a straightforward method, analogous to television or radio broadcasting, for performing simultaneous detection of multiple gases by use of wavelength modulation spectroscopy with diode lasers. When fiber-optic Coupled lasers are used, our approach guarantees that all beams transit the same optical path and impinge on the same detecter, Each laser is modulated at a different frequency and the detector output is processed by a set of lock-in amplifiers, one for each laser, to measure the absorbance encountered by each laser. # 1998 Optical Society of America OCIS codes: 300.0300, 300.6380, 140.2020, 140.3480, 130.6010, 060.4230.