A high-resolution velocimeter based on a fiber optic Sagnac interferometer

摘要

In this paper, we report a Sagnac interferometer based velocimeter with a resolution of 0.3μm/s. The sensor is constructed from commercially available telecommunication single mode fibers. A sensing probe is inserted on one side of the Sagnac loop to illuminate a test surface and to couple light back to the coil. Nonreciprocal phase shift appears between the counter-propagating waves when the surface is moving away or towards the sensing probe. A number of signal-to-noise-ratio enhancing techniques have been employed and a nanopositioner is also used to provide a known velocity to test the sensor response. Our experimental results have shown a linear relationship between the applied velocity and the sensor response within the nanopositioner restricted measurement range of 20μm/s.