Table 1.

Summary of the parameters of the tapered based RI sensors.

Type of the Sensor	Taper Geometry	Sensitivity/RIU Resolution RIU	RI Range	Reference
Single taper devices	Waist 60 μm	10−4 RIU	1.36–1.46	[43]
	Waist 7 μm	8.2 × 10−6	1.3330–1.3447	[61]
Mie scattering (silica nanoparticles)	Waist 2.8 μm	1.8 × 10−5 RIU	1.32–1.46	[63]
LPG	Waist 34 μm LPG 400 μm	1 × 10−4 RIU	1.30–1.34	[65]
	Waist 20 μm LPG ca. 400 μm	650 nm/RIU	1.00–1.36	[57]
	Waist 120 μm LPG 380 μm 6 periods	372 nm/RIU	1.33–1.46	[55]
	Waist 55 μm Length 3 mm	490.9 nm/RIU	1.3642–1.4015	[75]
MZI	Waist 25 μm LPG 300 μm	8.5 × 10−5	1.330–1.335	[64]
	Waist 63.75 μm LPG 414 μm	5.8 × 10−6 RIU	1.332–1.362	[67]
	Waist 54.6 μm LPG 564 μm	2066 nm/RIU	1.407–1.421	[30]
	Bi-taper length and waist 165 and 278 μm LPG period 550 μm and length 30 mm	−108.16 nm/RI	1.338–1.363	[92]
	Waist 66.5 μm Length 309 μm	7041.21 nm/RIU	1.4406–1.4458	[91]
FBG	Waist 30 μm	2.5−5 × 10−5	1.450–1.456	[68]
	-	1.63 ± 0.0 × 105 3.05 ± 0.01 × 105 dB/RIU	-	[70]
	6–8 μm	876–1233 nm/RIU	1.3380–1.3510	[76]
	Waist 90 μm LPG 500 μm	226.6 nm/RIU	1.33–1.38	[77]
	UFBT 167 μm DSB 82 μm	86.565 nm/cm/RIU	1.3332–1.4140	[21]
	Waist 40 μm	10−4 RIU	1.315–1.3618	[46,79]
Photonic crystals	Waist 71.7 μm	1529 nm/RIU	1.3355–1.413	[80]
	Waist 30 μm	1600 nm/RIU	1.3333–1.3577	[81]
	Waist 2 μm	190 nm/RIU	1.000–1.009	[85]
	Waist 60 μm	8.5 × 10−5	1.34–1.44	[82]
	Waist 70 μm	1426.70 nm/RIU	1.3917–1.4204	[83]
	Length 440 μm Waist 284 μm	281.6 nm/RIU	1.3333–1.3737	[84]
SPR	Waist 48 μm	3.2 × 10−5 RIU	1.33–1.40	[93]
	-	2 × 103 nm/RIU	1.335–1.380	[94]
	Waist 300 μm	15 × 103 nm/RIU	-	[95]
Multi-taper devices	Waist 52 μm Length 552 μm	261.9 nm/RIU	1.3333–1.3737	[73]
	Waist 76.5 μm and 13.2 μm	4000 nm/RIU	around 1.45	[39]
	Waist 17 μm Length 3 mm	500.6 nm/RIU	1.333–1.411	[74]
Bending at 45° and 90°	Waist 40 to 50 μm	126.15 nm/RIU at 90o	1.333–1.359	[90]
Fibre Loop Ring Down Technology	Waist 28.2 μm Length 728 μm	−388.581 μs/RIU	1.3333–1.3737	[87]
Sagnac loop	Waist 18, 13 and 9 μm Length: 16, 17 and 18 mm	3617 nm/RIU	1.33–1.41	[88]
Michelson interferometer	Length 20cm	1.35 × 104/RIU	1.3330–13470	[71]
	Waist 165–185 μm Bi-taper length is 375–490 μm Device length 20 mm	−178.424 dB/RIU	1.351–1.4027	[78]