Design on optical fiber methane sensing systems employing wavelength-scanning based differential absorption techniques

Utilizing a super-luminescent diode (SLD) in 1330 nm band and a fiber Fabry-Perot tunable filter (FFP-TF), an optical fiber methane sensing system is experimentally demonstrated. The differential absorption technique and a reference method are employed: a reference channel is introduced to eliminate the fluctuation of light source spectrum, and the two wavelengths are acquired by tuning the FFP-TF. The influence of the light source, loss of leading fiber, and the filters' variations are all avoided. A minimum detectable methane concentration of 0.15% achieved.