Multi-wavelength crosstalk-free photonic Doppler velocimetry

Multiplexed photonic Doppler velocimetry systems are developed to measure velocities with high density in physics experiments such as shock physics experiments on novel materials. Decreasing the mesh size can lead to crosstalk issues, which can be overcome by wavelength multiplexing. Crosstalk has been characterized on a line of eight collimators with a pitch of 1 mm. A crosstalk-free photonic Doppler velocimetry system with 16 telecom wavelengths was built. Wavelength multiplexing provides as well a reduction in the total number of fiber components. The system was designed for velocities up to 1000 m/s and with a bandwidth of 2 GHz. In the frequency domain, the channel spacing is 100 GHz, which is more than enough to prevent any crosstalk. A ramp compression experiment was carried out by a high-pulsed-power generator to demonstrate the dynamic performances of the crosstalk free system at about 80 m/s.