In optics, a Fabry–Pérot interferometer or etalon is typically made of a transparent plate with two reflecting surfaces, or two parallel highly reflecting mirrors.Its transmission spectrum as a function of wavelength exhibits peaks of large transmission corresponding to resonances of the etalon. It is named after Charles Fabry and Alfred Perot.
The SA200 and SA210 Series of Scanning Fabry-Perot (FP) Interferometers are high-finesse spectrum analyzers that are frequently used to examine the fine structure of the spectral characteristics of CW lasers. The confocal FP cavity acts as a very narrow bandpass filter. The transmission wavelength of the cavity is tuned by adjusting the length of the cavity using piezoelectric transducers, which are driven using the SA201 controller or an equivalent function generator. The transmitted light intensity is measured using a photodiode, amplified by the transimpedence amplifier in the SA201 (or equivalent amplifier) and then displayed / recorded by an oscilloscope or data acquisition card. For more information on confocal Fabry-Perot cavities, please see Thorlab's online tutorial.
...