A real-time displacement reconstruction method based on an all-fiber Fabry-Perot interferometer (FPI) is proposed, utilizing the fiber end face and the object surface to form an extrinsic FPI. Using the constant phase difference of 90 degrees between the two output ports of the 2 x 2 coupler, two-phase orthogonal FPI signals carrying the object motion information can be detected by two invisible photodetectors, and real-time displacement reconstruction can be realized by adopting inverse tangent and unwrapping processing procedures. Results show that the absolute errors of the experiment are below 80 nm.
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