Switching times in Fabry-Perot measurements

A key issue in developing pendular Fabry-Perot interferometer as very accurate displacement measurements device, is the noise level. The Fabry-Perot pendulums is the most promising device intended to detect gravitational waves, and therefore the background and the internal noise should be accurately measured and reduced. In fact terminal masses generates additional internal noise due mainly to thermal fluctuations and vibrations. We propose to exploit the reflectivity change, that occurs in some special points, to monitor the pendulum free oscillations and eventually estimate the noise level. We find that in spite of long transients, it is an effective method for noise estimate, further we prove that to retaining only the sequence of escapes, rather than the whole time dependent dynamics, entails the main characteristic of the phenomenon. This could also be relevant for future gravitational wave detector developments.