Real Time Velocity Measurement with All-fiber Self-mixing Speckle System

A novel method for real time velocity measurement is proposed. All-fiber laser measurement system is built by an erbium-doped fiber amplifier (EDFA). The measuring principle is based on laser self-mixing speckle, modulations of laser output caused by the optical feedback from an outer moving object. The generation of speckle signal is theoretically analyzed and experimentally obtained. A Labview programme is developed for waveform acquisition, noise reduction and numeric calculation. The signal processing shows a linear relationship between the energy density of speckle signal and the velocity of the moving object. In the experiments of real time velocity measurement by a rotating aluminum plate, we obtained measurement error less than 4.1% in the range of velocity from 234 to 508 mm/s. The study indicates that the all-fiber self-mixing speckle system can be applied in remote velocity sensing and measurement.