This study presents an original optical system designed for measuring the free surface velocity for shock wave diagnostics. The system is based on a solid Fabry–Perot etalon interferometer coupled to a tunable, single frequency laser. The setup assembled for this purpose can measure velocities up to 200 m s−1 and has a resolution time of about 1 ns. This system was validated in shock experiments performed on thin aluminum samples. The shock waves were generated by a pulsed laser on a water confinement configuration and the surface velocity was measured on the opposite side of the sample. The signals obtained are in good agreement with numerical simulation and results found in the literature. This system presents an interesting alternative to the velocity interferometer system for any reflectors (VISAR) commonly used in shock experiments.