Abstract

This paper describes a new multipoint simultaneous measurement in optical fiber laser Doppler velocimetry, which employs a laser diode modulated by injection current and many probes with an unbalanced optical fiber interferometer each. The beat shift frequency of each probe is set a different frequency by the difference in the optical path length of unbalanced illuminating fibers, and each velocity is calculated from the Doppler power spectrum with the beat shift frequency varying with each probe. Two-point simultaneous measurement is demonstrated in air flow with the measurement error less than 3.5% in velocity range of ±3 m/sec.

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