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-Pérot 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/µm. 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 µm range.
Funder
Fundação de Amparo à Pesquisa do Estado de São Paulo
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Cited by
1 articles.
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