Research on the enhancement of signal‐to‐noise ratio by radio frequency white noise in compact dense‐pattern multipass cell for trace gas detection

Abstract

The number of reflections is increased as much as possible in the optical multi-pass absorption cell to improve the effective optical path, but easily affected by light overlap resulting in light path interference. We present a novel strategy for suppressing the optical interference and improving the signal-to-noise ratio (SNR) with the radio frequency (RF) bandwidth-limited white noise. A linear output spectral response of the intensity with the CH4 concentration between 50 ppmv and 180 ppmv with a distributed feedback laser (DFB) at 1.653 μm was observed. The results show that the addition of RF noise effectively increases the laser line width and improves the SNR. About 3.6 gain in the SNR has been achieved using the RF noise, which led to a minimum detectable concentration of 0.03 ppmv (SNR = 1573). This performance level can reduce the difficulty of light adjustment and is very suitable for applications to trace gas sensing in harsh environment.

Ppb‐level CO2 sensor based on a miniature multipass cell with eight‐petaled spot pattern

“…[31][32][33] TDLAS technology, grounded in the Lambert-Beer law, asserts that extending the optical absorption path can substantially elevate detection sensitivity. 34,35 Multipass cells compact a lengthy absorption path into a smaller physical space, thereby reducing overall system size. 36 John U.…”