Multi-longitudinal mode 532 nm photonic Doppler velocimetry for shock experiments.

A novel multi-longitudinal mode 532 nm photonic Doppler velocimetry (PDV) was proposed to solve the problem of high bandwidth requirements in shock experiments with velocities up to km/s. Compared to the conventional PDV system operating at 1550 nm, the utilization of a shorter wavelength of 532 nm enables nearly three times the velocity resolution. However, it also leads to a threefold increase in the Doppler frequency shift for a given velocity. To mitigate the bandwidth constraints, a multi-longitudinal mode laser is employed to downconvert the signal, effectively reducing the bandwidth requirements. The efficacy of this method is validated through theoretical analysis and experimental investigations on detonation shock scenarios. Furthermore, this approach eliminates the necessity for modulators, frequency shifters, and other devices, facilitating its applicability to non-communication bands.

A hybrid system for simultaneous velocity and distance measurements in dynamic experiments.

The accurate measurement of an object's motion requires knowledge of both its position and its velocity. The commonly used photonic Doppler velocimetry and broadband laser ranging techniques are ideal for conducting simultaneous dynamic experiments. Instead of employing two distinct measurement systems, we developed a hybrid system that can simultaneously measure velocity and distance in dynamic experiments. This reduces cost and complexity, particularly for multi-channel tests, by using only one probe, photodetector, and oscilloscope channel. By precisely synchronizing the velocity and distance data in time, the system can assist with interpreting the target's position and orientation.

Multi-reference broadband laser ranging to increase the measuring range.

Broadband laser ranging (BLR) is an appropriate method to obtain absolute distance in dynamic experiments. In this article, we first analyze the performance limit for BLR and indicate that the measuring range can be hardly increased while keeping the distance or time resolution unchanged. Then, multi-reference BLR is proposed, which can break this limit and greatly increase the measuring range. Its validity is demonstrated by an experiment with an explosively driven aluminum surface flying over 100 mm. This method would improve the capability of BLR.