All-fiber differential interferometer for nanometric displacement measurement

An all-fiber differential interferometer is proposed to measure nanometric displacements based on the characteristics of unidirectional transmission of light in the circulator. In the new interferometer system, one laser is used as the light source, and two circulators are used as two independent homodyne interferometers to constitute the differential optical-path. Thus, two interference signals are generated without affecting each other. Subsequently, object displacement is reconstructed by comparing the phases of the signals. In this study, the feasibility of the proposed method is demonstrated by experimental measurements, and results show that the standard deviation is in the order of 1 nm.