Self-Mixing Interferometry on Long Distance: Theory and Experimental Validation

We consider the operation of a self-mixing interferometer on distances larger than the laboratory scale, that is, tens to hundreds of meters, and develop for the first time the theoretical analysis of SMI performances in the near and far field (FF), presenting results about signal amplitude (AM), SNR, C factor, spot size, and linewidth. Theory is also valid for the realistic case of an elliptical laser spot. Thereafter, we compare the theoretical findings with experimental data measured on white paper target using a diode laser SMI operating at 1550 nm, with a SNR =3.6 at 12-m distance and find good agreement. These results open the way to long stand-off vibration, displacement, and distance/velocity measurements.