Interferometric sensors, known for their high accuracy, often have limited measurement range due to the periodicity of their signal. This paper introduces a cavity-based interferometry concept using a laser with moderate coherence, combining ultra-high accuracy with ultra-high measurement bandwidth and range. Mid-fringe detection and interferometric visibility measurements are combined. Experimental results for length sensing show 1 nm accuracy with a 120 µm range (0.00083% relative uncertainty) and a bandwidth from 0 Hz to 20 kHz.

Johannes Dickmann, Liam Shelling Neto, Steffen Sauer, Stefanie Kroker