Optical EngineeringMethod to minimize spurious background signals in gas detectors based on correlation spectroscopy using a Fabry-Pérot bandpass filter shape optimization
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The parasitic background signal produced by gas detectors using a Fabry-Pérot interferometer (FPI) as a modulator is shown to be very sensitive to the infrared bandpass filter characteristics. This parasitic signal is generally the feature limiting the sensitivity of such devices. We review this problem, and provide a general approach to filter choice that minimizes the background amplitude for this kind of detection system. It is shown that in general filters with very abrupt transitions from the stop to passband are in fact undesirable, and fortuitously the optimum choice of filter leads to easily realized, low-cost designs.