Displacement Measurement Using Two-Photon Absorption Process in Si-Avalanche Photodiode and Fiber Bragg Gratings

Abstract

This paper proposes a displacement measurement system using two-photon absorption (TPA) process in a Si-avalanche photodiode and fiber Bragg gratings (FBGs). The use of TPA process eliminates high-frequency and complicated RF circuits usually required for intensity correlation measurements. By controlling the phase difference between the modulation signals for probe and reference light, the displacements of FBGs are precisely measured. Small displacement of an FBG by 0.4 mm was successfully measured in the proof-of-concept experiment.