X-Nico

Optical ring resonators

where $\backslash mathcal\{F\}$ is the finesse of the ring resonator, $\backslash nu\; \{f\}$ is the free spectral range, and $\backslash delta\backslash nu$ is the full-width half-max of the transmission spectra.

Tunable diode laser absorption spectroscopy

Another way to measure the temperature is by relating the FWHM of the probed absorption line to the Doppler line width of the species at that temperature.

see also