Table 1.

Summary of the best experimental performances for fiber optic plasmonic refractometers

Sensor configuration	Wavelength range	Ultimate bulk refractometry	Figure of merit	Reference
I. Geometry-modified fibers
Unclad/etched fiber	500–800 nm	ca. 4,000 nm/RIU	ca. 40	[19–22]
Side-polished/D-shaped fiber	500–800 nm	ca. 3,200 nm/RIU	ca. 64	[23–27]
Tapered fiber	500–800 nm	ca. 11,800 nm/RIU	ca. 118	[28–34]
Hetero-core structure	500–800 nm	ca. 5,000 nm/RIU	ca. 33	[35, 36]
U-shaped fiber	500–800 nm	ca. 30 ΔA/RIU	N/A	[37]
Arrayed fiber end face	500–1,600 nm	ca. 120 nm/RIU, ca. 17 ΔI/RIU	ca. 1	[38–41]
II. Grating-assisted fibers
LPFGs	800–1,200 nm	ca. 10 ΔT/RIU	N/A	[44]
TFBGs	1,500–1,600 nm	ca. 500 nm/RIU	ca. 2,500	[46, 50–52]
III. Specialty fibers
Polarization maintaining	ca. 800 nm	ca. 3,200 nm/RIU	ca. 40	[54]
Microstructured	500–800 nm	ca. 6,430 nm/RIU	ca. 90	[55–62]*
Polymer	700–800 nm	ca. 1,300 nm/RIU	ca. 9	[63–65]

ΔA/RIU absorption change per refractive index unit, ΔT/RIU transmission change per refractive index unit, ΔI/RIU intensity change per refractive index unit, N/A not applicable

*Only theoretical values