Study of Wavelength-Dependent Bend Loss in Step-Index Multimode Fiber-Optic Microbend Displacement Sensor

In this article, the wavelength dependence of bend loss in a step-index multimode optical fiber (100 µm core diameter; fused silica) was investigated for fiber bend radii ranging between 2.0 and 4.5 mm using six excitation wavelengths, namely, 337.1, 470, 590, 632.8, 750 and 810 nm. The results obtained from fitting the bend loss measurements to Kao's model and utilizing MATLAB indicate that bend loss is wavelength dependent and transmission loss in multimode optical fibers increases with the decrease in the fiber bend radius. Furthermore, the response of a microbend fiber optic displacement sensor was characterized at 337.1, 470, 632.8, 750 and 810 nm. Measurements obtained from the microbend sensor indicate that the sensor output power is linear with the applied displacement and the sensor output is wavelength dependent.