New all-fiber velocimeter

A new all-fiber velocity interferometer system for any reflector (AFVISAR) was developed. It was conceived and realized with the purpose of using it as the basic measuring element of a complete system for multiple point velocity measurements. Its main features are that it works at 532nm and partly adopts the multimode optical fiber. The velocimeter consists of only fibers or fiber coupled components and has no optic elements such as optic lenses or reflectors. It is therefore very compact and easy to operate. Unlike the conventional AFVISAR, which uses single-mode optic fiber components, the laser beam in this new interferometer system arrives at and reflects from the target surface through a multimode optical fiber component, and then enters and interferes in a [3×3] single-mode fiber coupler. Its working principle is elaborated on in this article. Preliminary experiments using a split Hopkins pressure bar (SHPB) device show that the new interferometer can successfully measure the velocity profiles of the metal specimen along the axial or radial direction. Further experiments on a one-stage gas gun are under consideration.