Oscillating optical fiber speckle patterns: modeling and application

Author(s)

Fujiwara, Eric ; Wu, Yu Tzu ; Suzuki, Carlos K.

• Document type: Journal article
• Source: OPTICS CONTINUUM; v. 1, n. 12, p. 13-pg., 2022-12-15.

Abstract

Speckle patterns produced by the interference between multiple optical fiber modes carry detailed information regarding the waveguide characteristics. However, reflection-type setups implemented with fiber coupler and mirror generate oscillating specklegrams that cycle consistently around well-defined states. To study such a peculiar phenomenon, an analytical model derived from a multimode fiber Fabry-Perot interferometer investigates the contributions of the cavity length, refractive index, and laser wavelength, revealing a sinusoidal modulation of the correlation coefficient. Experiments confirm the effect of the fiber-mirror distance on the specklegram changes: computing the correlation and tracing the spatiotemporal evolution of a light granule through active contour models yielded a phase sensitivity of 15.71 rad/mu m. Furthermore, the presented system works as a precise displacement sensor enhanced by the extended correlation algorithm, achieving 3 nm resolution with linear response over a 70 mu m range. (AU)

• FAPESP's process: 17/25666-2 - Development of an optical fiber force myography sensor for applications in human-robot interfaces
• Grantee: Eric Fujiwara
• Support Opportunities: Regular Research Grants