Table 3.

RMSE of the calibration interpolating functions in Fig. 5.

RMSE (${\mathrm{cm}}^{-1}$)	Second-order	Third-order	Fourth-order
Device 1	3.56	3.49	3.47
Device 2	0.98	0.92	0.91
Device 3	0.76	0.60	0.52