Abstract
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.
Highlights
Laser Doppler Velocimetry (LDV) came into use in the middle of the 1960s with the frequency shift measurement of a He–Ne laser through liquid excited by an ultrasonic wave.1 Right after that, flow velocity measurements of gases and liquids were reported.2,3 Velocity measurements to study the dynamic mechanical properties of materials were initiated in the middle of the 1960s.4 A few years later, the VISAR5 (Velocity Interferometer System for Any Reflector) became more and more available and has since been used for shock physics experiments on novel materials
When the time resolution gets too limited by the interference fringe size, slightly modified Photonic Doppler Velocimetry (PDV) systems are used with signal processing based on phase analysis
We presented a multi-wavelength crosstalk-free photonic Doppler velocimetry system with 16 channels
Summary
Laser Doppler Velocimetry (LDV) came into use in the middle of the 1960s with the frequency shift measurement of a He–Ne laser through liquid excited by an ultrasonic wave.1 Right after that, flow velocity measurements of gases and liquids were reported.2,3 Velocity measurements to study the dynamic mechanical properties of materials were initiated in the middle of the 1960s.4 A few years later, the VISAR5 (Velocity Interferometer System for Any Reflector) became more and more available and has since been used for shock physics experiments on novel materials. The increase in the number of channels could create crosstalk issues if the physical spacing between the measurement points reduces. It is the case on 3D carbon materials.14 This crosstalk issue can be canceled by wavelength multiplexing if the channel spacing is greater than the maximum Doppler frequency.
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