Light control of a movable microbubble in an ethanol-filled fiber microcavity for displacement measurement

An optical fiber displacement sensor based on a lightcontrolled microbubble in an ethanol -filled fiber microcavity is proposed. The single -frequency 1550 nm laser in the side -lead-in single -mode fiber (SMF) produces an uneven temperature gradient by side irradiation in the ethanolfilled fiber microcavity. The microbubble shifts to the laser irradiation position along the microcavity due to the Marangoni effect and finally stops at the laser irradiation position. When the side -lead-in SMF moves, the microbubble follows. The surfaces of the microcavity and microbubble form a Fabry-Perot interferometer (FPI). The optical path difference (OPD) of the FPI is demodulated by the position of the side -lead-in SMF, which can be used for the displacement measurement with ultrahigh sensitivity (1.1 x 10-3 nm-1/mu m). What is more, the proposed structure is only sensitive to a one-dimensional direction and has the advantages of non -contact, large range, and high resolution, which makes it a perfect candidate for displacement sensors. (c) 2024 Optica Publishing Group