Remote System for Detection of Low-Levels of Methane Based on Photonic Crystal Fibres and Wavelength Modulation Spectroscopy

Table 1

Theoretical diffusion times to obtain 90% average methane concentration in the core of HC-PCF fibres for different lengths.

	One open end		Two open ends
ℓ (m)	t (s)	t (min)	t (s)	t (min)
0.02	16	0.27	4	0.07
0.06	136	2.27	34	0.57
0.18	1220	20.33	305	5.08
0.54	10980	183	2745	45.75