Utilizing a super-luminescent diode(SLD) in 1 330 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 detec...