We describe a method for distinguishing optical modes of a resonator based on the characterization of the temperature sensitivity of a mode’s resonance frequency and its dispersion characteristics. This method requires an interrogator (made up of a tunable laser, broadband light source, frequency comb, or some combination thereof) capable of measuring resonator response spanning one or more free spectra range(s). This moderately broadband spectrometer is used to acquire spectra spanning multiple FSR over multiple temperatures/pressure/stimuli to characterize the stimuli specific (e.g. temperature) sensitivities of individual modes and the mode spacing (FSR) dependence on the stimuli. The stimuli (temperature) dependence of the mode frequency and dispersion is then used to uniquely identify the mode number of the observed mode, allowing the user to match the correct calibration coefficients to the mode under observation.
The invention is a method for utilizing a moderately broadband spectrometer to utilize the mode frequency (vm), mode-to-mode separation (FSRmn), and their respective dependence on a thermophysical perturbation (e.g. temperature) to uniquely label each mode.
The methodology described here allows us to use lower SWAP value lasers in lieu of more expensive lasers, broadband lasers. This is expected to lead to a factor-of-five or more reduction in instrument cost.