QLI Labs has developed fiber optics, phase-resolved, swept-source low-coherence interferometer, which detects sub-nanometer path-length changes at sub-millisecond time-scales. The common path geometry renders extremely stable phase measurements, while the swept-source laser allows for super-fast detection. For example, we can detect evaporation rates of water droplets (i.e. thickness changes), which are found to be in the range of 1 nm/ ms.