Fig. 1. Structure diagram of optical fiber preform. (a) Structure diagram of optical fiber; (b) refractive index dispersion diagram

Fig. 2. Optical fiber loss spectrum

Fig. 3. Flowchart of preparation process of infrared coherent fiber bundle by the once stack-and-draw technique. (a) Single-fiber drawing of optical fiber; (b) preform of multi-fibers; (c) drawing of coherent fiber bundle; (d) end-face image of coherent fiber bundle taken by optical microscope

Fig. 4. Handheld near-infrared microscope capturing the end face image of the coherent fiber bundle

Fig. 5. Coherent fiber bundle resolution testing system and results. (a) Schematic diagram of the system; (b) resolution plate image; (c) group 3, items 4, 5, and 6; (d) groups 4 and 5

Fig. 6. Crosstalk rate testing system and results. (a) Schematic diagram of the system; (b) homemade diaphragm (perforated aluminium foil); (c) test results graph; (d) light input into two fibers graph

Fig. 7. Infrared imaging temperature resolution testing system and results. (a) Schematic diagram of the system; (b) thermal camera image; (c) infrared camera recorded image (after background removal)

Fig. 8. Infrared coherent fiber bundle imaging temperature resolution testing system and results. (a) Schematic diagram of the system; (b) thermal camera image; (c) infrared camera recorded image (after background removal)