Techniques and accuracy of determining the target acceleration from the spectrum of a laser autodyne signal in the presence of nonlinear effects caused by external optical feedback

Two autodyne (self-mixing) laser interferometry methods for determining microscale-motion parameters are considered, which are based on the analysis of the Fourier spectrum of a laser autodyne signal and use features of the spectra of interference signals from objects moving with a constant acceleration, including a possibility to accurately approximate such spectra by simple functions expressed in terms of the Fresnel integrals. The potential of using these methods under different levels of external optical feedback, which changes the generation conditions of the laser diode, and a relatively high noise level typical of autodyne laser-diode-based interferometers is assessed by means of numerical simulation. The influence of external optical feedback on the spectrum of the signal of an autodyne interferometer from a target moving with a constant acceleration is studied. It is shown that the nature of changes in the spectra of signal fragments with increasing feedback strength makes it possible to use the methods under consideration when the measurements are performed in the weak feedback regime. For both methods, conditions concerning the choice of signal fragments to analyze for achieving good accuracy in estimating motion parameters are found.