4. Conclusions
Fiber laser intracavity absorption spectroscopy (FLICAS) wasused to simultaneously measure temperature, CO concentration,and CO2 concentration in the temperature range 296–1200 K. The methane concentration can be measured only at temperatures lower than 373 K, due to deficient data in the HITRAN database related to “hot” transitions. The temperature can be measured using CO2 lines in the 6390–6410 cm−1 range or using CO spectral lines in the vicinity of the bandhead (6408–6418 cm−1 range). The sensitivity to CO is about 400 ppm at room temperature and about 0.2% at 1200 K. The sensitivity to CO2 is between 1 and 10% depending on temperature. This range of sensitivities makes FLICAS sensors suit-able for many applications, although it can be improved at least an order of magnitude by increasing the generation time.The main advantages of FLICAS measurements are the possibility of simultaneously measuring CO, CO2 and temperature in a very short time (3.7 s in this work, without averaging) and operating under conditions of strong broadband absorption or light scattering, which are common in flames and other harsh environments. Accurate absolute concentration measurements demand knowledge of the optical path length. When this cannot be easily determined, calibration against known concentrations is required.