Enhanced laser self-mixing interferometry based on tunable Fabry-Perot Filter

In this paper, an enhanced laser self-mixing interferometry based on tunable Fabry-Perot Filter is proposed. The frequency-modulated (FM) self-mixing signal is transformed into intensity variations by a Fabry-Perot Filter, which transforms laser frequency variations into intensity variations when the laser wavelength is set to the edge of the Fabry-Perot Filter steep transmission profile. We compared the enhanced approach with the conventional SMI. The magnitude of obtained F-P enhanced SMI signal is about 40 times stronger than that from conventional SMI. The new approach can improve signal-to-noise ratio and extend the applicability of SMI into new fields allowing lower backscattering signals. Our approach overcomes the spectral range limitation of some optical edge filtering approach, since the wavelength of Fabry-Perot Filter can be changed to match the different lasers for an enhanced SMI signal.