Displacement measurement using phase-shifting optical feedback interferometry

A laser sensor using optical feedback interferometry has been designed to measure displacements up to several micrometers. For this purpose a Lithium Niobate crystal generates a phase-shift in order to modulate at a frequency of 580 kHz the optical path difference between the sensor and the target. This setup has been calibrated by means of a commercial optical fiber sensor. The overall accuracy resulted to be up to 40 nm, for a 1 kHz sinusoidal motion of the target at 10 cm away from the sensor.