The authors describe an optical fibre laser Doppler velocimeter (FLDV) system which consists of a manipulator that is easy to handle and a small probe. The manipulator, with a tilting mechanism of 0.3 mu m resolution, has been developed to achieve a high transmitting efficiency of laser power into a single-mode fibre. A beam expander with a perforated lens is used in the probe in order to improve the quality of the measurement volume and to reject light scattered at the front lens. The performance of the FLDV was examined by measuring the tangential velocity of a rotating disc and the longitudinal velocity of turbulent water in a pipe at three flow rates. The results show an excellent performance of the FLDV.
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