Table 4.

Calculation of uncertainties of the second method experimental setup at ${\lambda }_{WM}\approx 1530\mathrm{nm}$ and for a period of time of 30 min, corresponding to n = 2245.

Magnitude	Component of Uncertainty	Value (pm)	Type	Uncertainty Contribution (pm)
${\lambda }_{ref}$	Absorption line value	3.5 × 10−1	B	1.8 × 10−1
λFBGI	Measurement stability	6.0 × 10−4	A	1.3 × 10−5
	Optical resolution	8.0 × 10−1	B	2.3 × 10−1
	Display resolution	1.0 × 10−2	B	2.9 × 10−3
	On-off repeatability	2.0 × 10−1	B (*)	1.2 × 10−1
	Expanded uncertainty (U) (k = 2)			±6.3 × 10−1

(*) Obtained by experimentally estimating the lower and upper bounds.