Fig. 1. (a) Sketch of the Kretschmann prism configuration used for plasmonic sensing; (b) its sensing principle

Fig. 2. Sketch of the plasmonic sensor based on fiber grating

Fig. 3. (a) Sketch of the uniformfiber grating and its transmission (black curve) and reflection (red curve) spectra; (b) sketch of the tilted fiber gratings and its transmission; (c) sketch of the eccentric fiber gratings and its transmission; (d) sketch of the excessively tilted fiber gratings and its transmission; (e) sketch of the long-period fiber gratings and its transmission

Fig. 4. Sketch of the SPR excitation around an optical fiber showing the required polarization of the electric field

Fig. 5. Plasmonic enhancementin gold-coated TFBG (blue curve and right-up inset) versus evanescent field TFBG in a normal bare fiber (red curve and right-down inset)

Fig. 6. Transmission spectra of a gold coated TFBG. (a) P-polarized incident light with SPR excited; (b) S-polarized incident light without SPR excited

Fig. 7. Sketch of phase mask based fiber grating inscription system

Fig. 8. (a) Sketch of the sputtering deposition of optical fiber coating; (b) principle of rotation coating method to obtain uniform thickness film layer; (c) microscope and scanning electron microscope view of a gold coated fiber surface

Fig. 9. Sketch of typical fiber optic sensor for bio-functionalization and specific measurement methods

Fig. 10. Scheme of fiber SPR sensors interrogation. (a) Wavelength interrogation; (b) intensity interrogation

Fig. 11. (a) TFBG SPR refractive index response spectral; (b) linear relationship between TFBG SPR refractive index and SRI changes

Fig. 12. Plasmonic TFBG cell intensity sensor[130]

Fig. 13. Plasmonic TFBG urinary protein sensor[127,128]

Fig. 14. Plasmonic TFBG glucose concentration sensor[131]

Fig. 15. Plasmonic TFBG electroactive microbe sensor[132]

Fig. 16. Plasmonic TFBG neurotransmitter sensor[133]

Fig. 17. Plasmonic TFBG gas sensor[40]

Fig. 18. (a) Picture of the packaged plasmonic fiber grating sensor; (b) biosensor inserted in a freshly biopsied tissue and its corresponding amplitude spectrum; (c) packaged sensor inserted in the operating channel of an endoscope[125]