This paper presents the design and application of a compact, single-ended laser-absorption sensor for measuring temperature and H2O in high-temperature combustion gases. The sensor employs two fiber-coupled, near-infrared diode lasers and a fiber bundle for pitching the laser light and collecting the light that is backscattered off a native surface. The transmitting and receiving end of the sensor is housed within a 1/8” NPT pipe fitting along with a 6 mm diameter lens to increase the collection efficiency. These attributes enable the sensor to be directly integrated into a sealed, high-temperature environment without windows. The sensor was demonstrated with measurements of temperature and H2O mole fraction in a burner using calibration-free wavelength-modulation-spectroscopy techniques with a measurement bandwidth up to 25 kHz.
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