Toward single-ended absorption spectroscopy probes based onn backscattering from rough surfaces: H2O vapor measurements near 1350 nm

摘要

We demonstrate feasibility of a new class of absorption spectroscopy sensors which use return scattering from native surfaces such as the piston of an automotive engine. Our demonstration experiment collects backscatter through a 2-mm-diameter aperture, consistent with a small sensor footprint. A 20 mW DFB laser is used, but only 10 A mu W is collected. We studied the noise associated with motion of the rough surface and found an RMS level of 7 %. Wavelength modulation spectroscopy (WMS) was use