We present the design and fabrication of a novel fiber optic multiparameter bend sensor. Unlike current intrinsic fiber optic multiparameter bend sensors that depend on multiple cores or multiple fibers, the new sensor is based on three circumferential active-cladding point modifications on a single optical fiber at specific axial locations along the length of the fiber. A commercial 30-W CO2 laser is used to cut three point modifications in the plastic cladding of the fiber. Each of the three defects is filled with fluorophores (quantum dots) with different peak emission wavelengths. A 405-nm laser (operating at 10-mW) is used to excite the quantum dots, while a spectrometer, coupled to the fiber, measures the emission signals of each of the three fluorophores simultaneously. Results show that bending direction and degree of curvature at a single localized modification region can be expressed as a function of the three fluorescence intensities.
Colonoscopy is the current gold standard for colon cancer screening and diagnosis. However, the near-blind navigation
process employed during colonoscopy results in endoscopist disorientation and scope looping, leading to missed
detection of tumors, incorrect localization, and pain for the patient. A fiber optic bend sensor, which would fit into the
working channel of a colonoscope, is developed to aid navigation through the colon during colonoscopy. The bend
sensor is comprised of a bundle of seven fibers doped with quantum dots (QDs). Each fiber within the bundle contains a
unique region made up of three zones with differently-colored QDs, spaced 120° apart circumferentially on the fiber.
During bending at the QD region, light lost from the fiber's core is coupled into one of the QD zones, inducing
fluorescence of the corresponding color whose intensity is proportional to the degree of bending. A complementary
metal oxide semiconductor camera is used to obtain an image of the fluorescing end faces of the fiber bundle. The
location of the fiber within the bundle, the color of fluorescence, and the fluorescence intensity are used to determine the
bundle's bending location, direction, and degree of curvature, respectively. Preliminary results obtained using a single
fiber with three QD zones and a seven-fiber bundle containing one active fiber with two QDs (180° apart) demonstrate
the feasibility of the concept. Further developments on fiber orientation during bundling and the design of a graphical
user interface to communicate bending information are also discussed.