Proceedings Article | 29 August 2013
KEYWORDS: Interferometers, Polarization, Visibility, Beam splitters, Single mode fibers, Calibration, Doppler effect, Optical components, Reflectors, Fiber optics
Acceleration measurement plays an important role in a variety of fields in science and engineering. In particular, the
accurate, continuous and non-contact recording of the shock acceleration profiles of the free target surfaces is considered
as a critical technique in shock physics. Various kinds of optical interferometers have been developed to monitor the
motion of the surfaces of shocked targets since the 1960s, for instance, the velocity interferometer system for any
reflector, the fiber optic accelerometer, the photonic Doppler velocimetry system and the displacement interferometer.
However, most of such systems rely on the coherent quasi-monochromatic illumination and discrete optic elements,
which are costly in setting-up and maintenance. In 1996, L. Levin et al reported an interferometric fiber-optic Doppler
velocimeter with high-dynamic range, in which fiber-coupled components were used to replace the discrete optic
elements. However, the fringe visibility of the Levin’s system is low because of the coupled components, which greatly
limits the reliability and accuracy in the shock measurement. In this paper, a compact all-fiber interferometer system for
measuring the shock acceleration is developed and tested. The advantage of the system is that not only removes the
non-interfering light and enhances the fringe visibility, but also reduces polarization induced signal fading and the
polarization induced phase shift. Moreover, it also does not require a source of long coherence length. The system bases
entirely on single-mode fiber optics and mainly consists of a polarization beam splitter, a faraday rotator, a depolarizer
and a 3×3 single-mode fiber coupler which work at 1310 nm wavelength. The optical systems of the interferometer are
described and the experimental results compared with a shock acceleration calibration system with a pneumatic exciter
(PneuShockTM Model 9525C by The Modal Shop) are reported. In the shock acceleration test, the interferometer system
measured shock acceleration with peak accelerations of ~100,000 m/s2 and the durations of ~0.2 ms which are
conformed to the results of the shock acceleration calibration system. The measured relative error of the acceleration is
within 3%.
