Fig. 1. Sensing structure. (a) Structure schematic of sensor; (b) sensing structure under microscope;(c) graphene quantum dots (GQDs) under scanning electron microscope

Fig. 2. Initial transmission spectra of thin-core fiber. (a) Before tapering; (b) after tapering

Fig. 3. Spectral lines of sensor after coating with graphene quantum dots-polyvinyl alcohol (GQDs-PVA). (a) Initial transmission spectrum; (b) spectral analysis

Fig. 4. Schematic of temperature and humidity experimental apparatus

Fig. 5. Temperature experimental results of sensor before and after tapering. (a) Temperature drift before tapering; (b) temperature fitting before tapering; (c) temperature drift after tapering; (d) temperature fitting after tapering

Fig. 6. Temperature experimental results of sensor after coating GQDs-PVA. (a) Temperature drift; (b) temperature fitting

Fig. 7. Temperature stability of sensor after coating GQDs-PVA

Fig. 8. Humidity experimental results of sensor after coating GQDs-PVA. (a) Relative humidity drift; (b) relative humidity fitting

Fig. 9. Humidity stability of sensor after coating GQDs-PVA