Fig. 1. Design of sensors. (a) Sensor structure diagram; (b) 3D printed model drawing; (c) sensor plane grinding diagram; (d) sensor tilted surface grinding diagram; (e) actual cross-sectional image of sensor

Fig. 2. Physical diagram of experimental detection system

Fig. 3. Schematic diagram of coupling between incident light and receiving fibers

Fig. 4. Comparison curves for different tilt angles

Fig. 5. Comparison curves of output powers for different incident fiber radii

Fig. 6. Comparison curves of output powers for different receiving fiber radii

Fig. 7. Simulation results of three parameters. (a) Comparison curves for different amounts of misalignment; (b) comparison curves for different inner fiber spacings; (c) comparison curves for different outer fiber spacings

Fig. 8. Analysis of variation of light intensity with light path. (a) Analysis of light intensity variations for different light paths; (b) linear fitting for different light paths

Fig. 9. Growth of Trichoderma longibrachiatum on surface of tissue paper. (a) Surface morphology; (b) 148 μm; (c) 264 μm and 212 μm; (d) 468 μm

Fig. 10. Information of Trichoderma longibrachiatum on surface of tissue paper samples. (a) Absorbance information; (b) correspondence between mold height and absorbance

Fig. 11. Growth of Trichoderma longibrachiatum on surface of rough edge paper. (a) Surface morphology; (b) 262 μm; (c) 509 μm; (d) 194 μm and 375 μm; (e) 104 μm

Fig. 12. Information of Trichoderma longibrachiatum on surface of rough edge paper samples. (a) Absorbance information; (b) correspondence between mold height and absorbance

Fig. 13. Growth of Trichoderma longibrachiatum on surface of ink-dyed paper. (a)‒(e) Tissue paper; (f)‒(k) rough edge paper

Fig. 14. Information of Trichoderma longibrachiatum on surface of ink-dyed paper samples. (a) Spectrum of tissue paper; (b) spectrum of rough edge paper; (c) relationship between height of mold on surface of tissue paper and absorbance; (d) relationship between height of mold on surface of rough edge paper and absorbance