Reply to “Comment on ‘Thermal phase noise in Fabry-Pérot resonators and fiber Bragg gratings’ ”

Abstract

The previous Comment clarifies a few key points that were unclear in an earlier paper by its authors, in particular their definitions of phase and of phase noise. We now agree that this earlier paper was modeling the resonance-frequency fluctuations of a Fabry-Perot resonator, whereas our article [Phys. Rev. A 89, 033818 (2014)] was modeling the noise in the phase of the resonator's output field. In light of the Comment, the two pictures are indeed consistent. The resonance-frequency fluctuations are independent of group index, whereas the phase noise in the output field is proportional to group index. This important dependence was pointed out in our paper [Phys. Rev. A 89, 033818 (2014)]. From a more physical standpoint, we argue that phase noise can be described without resorting to the concept of signal-to-noise ratio and that, although the phase noise is of course in part a property of the fiber itself, its group-index dependence is introduced solely by the resonator.