Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
(a) Schematic structure of the test system for diffusing gas detection. MFC: mass flow controller; PA: photoacoustic; DFB: distributed feedback. (b) Absorption coefficients of 1 ppm CH4 and interfering gases in the spectral range from 1640 nm to 1660 nm.
