Optical Path Length Calibration: A Standard Approach for Use in Absorption Cell-Based IR-Spectrometric Gas Analysis

Figure 1

Schematic diagram of the setup used to calibrate the optical path length of a gas cell under test (CUT) with 𝐿 = 21 m (nominally). The reference cell has a nominal optical path length of 0.2 m. PD: photodiode. FP: Fabry-Perot etalon (removable).