Simultaneous broadband laser ranging and photonic Doppler velocimetry for dynamic compression experiments

Abstract

A diagnostic was developed to simultaneously measure both the distance and velocity of rapidly moving surfaces in dynamic compression experiments, specifically non-planar experiments where integrating the velocity in one direction does not always give the material position accurately. The diagnostic is constructed mainly from fiber-optic telecommunications components. The distance measurement is based on a technique described by Xia and Zhang [Opt. Express 18, 4118 (2010)], which determines the target distance every 20 ns and is independent of the target speed. We have extended the full range of the diagnostic to several centimeters to allow its use in dynamic experiments, and we multiplexed it with a photonic Doppler velocimetry (PDV) system so that distance and velocity histories can be measured simultaneously using one fiber-optic probe. The diagnostic was demonstrated on a spinning square cylinder to show how integrating a PDV record can give an incorrect surface position and how the ranging diagnostic described here obtains it directly. The diagnostic was also tested on an explosive experiment where copper fragments and surface ejecta were identified in both the distance and velocity signals. We show how the distance measurements complement the velocity data. Potential applications are discussed.

Shock Measurements Based on Pendulum Excitation and Laser Doppler Velocimetry: Primary Calibration by SI-Traceable Distance Measurements

“…In either case, if a shock system that includes a moving test block is not readily available, then mechanical calibration with a suitable rotating system, such as that described in Refs. [14] and [15], may prove useful and simple to implement.…”

Frequency-Modulated Chirp Signals for Single-Photodiode Based Coherent LiDAR System

“…In the single-photodiode-based coherent receiver with LO as a chirp signal, the LO and the out-going signal are usually split after amplification at the transmitter, for example by an Erbium-doped fiber amplifier (EDFA) [24], [30]. In this case, both the transmitted signal and LO are corrupted by amplified spontaneous emission (ASE) noise.…”

“…At the receiver, the polarization states of the Rx signal and LO were first aligned by two polarization controllers (PCs) to maximize the beating [26], [30], and then combined with a 3-dB coupler. The LO power at the input of the 3-dB coupler was 13.4 dBm and the Rx signal power was swept from −10.6 dBm to −66.8 dBm with a step size of −5 dB.…”

Ultrafast Fiber Bragg Grating Interrogation for Sensing in Detonation and Shock Wave Experiments

“…This approach differs from the previously published CFBG interrogation method described in [1,2,4] in that the detection in the time-stretch streaked approach fully resolves the CFBG spectrum and is sensitive to spectral changes in real time, whereas the original CFBG approach [11,12,13] is only sensitive to time changes in the integrated CFBG spectrum. In both approaches, the CFBG sensor still offers a common benefit to researchers seeking embedded fiber detection of dynamics when a minimally-intrusive embedded sensing method is desired or when direct line of sight optical access (i.e., streak camera, optical ranging [14], PDV [15], VISAR [16], etc.) is not possible.…”