Standard sensor calibration test in angular interrogation scheme. Reflectance spectra as a function of incident angle of the sensor device obtained by injecting different weight percentage concentration of glycerol in distilled water (0.1–0.5% w/v): (a) at 1250 nm, (b) at 850 nm, (c) 650 nm, and (d) 530 nm. The refractive index difference between DI water and the level of glycerol concentration evaluated is shown in the legend.