Theoretical analysis and experimental investigation of optical fiber curvature sensors
Student thesis: Doctoral Thesis
An optical fiber curvature sensor with topological features built directly onto the optical fiber is elaborated in this thesis using, amongst others, the theory of light propagation through bent optical fibers. Bending the optical fibers alters the propagating rays' trajectories, concentrating them on the outer (convex) side of the bend in proportion to the bend curvature. A purposely built loss ("sensitive") zone on the convex fiber-side captures this modulation effect in the form of the correspondingly reduced intensity of light transmitted to the output fiber end. In order to better understand such sensor quantitatively, a number of research directions have been explored. This includes the analysis within the domain of physical optics applied to the bent optical fiber, ray tracing simulations based on the principles of geometric optics, and pourer loss calculations using the transmission coefficient formulas. As a result, the relationship between the sensitivity and dimensions of the sensor's pre-built sensitive zone are established. This has been verified experimentally. An optimal sensitive zone with a maximum response to curvature has been specified. It has been shown that the sensitivity of the curvature sensor depends strongly- on the dimensions of its "sensitive zone", and this dependence has been defined.
- Optical fiber detectors