A variable valve mechanism of an internal combustion engine capable of changing at least one of two valve physical quantities, i. The present invention first estimates a first feedback weight of the mobile unit during a first slot. This method utilizes the same narrow band-pass spectral filter for the detection of the gas of interest for both the signal and the reference channels. Preferably, within the passage a connector is adapted to electrically connect the inner conductor of the coaxial cable and the lead wire. The first optical adhesive layer is located between the first substrate and the second substrate.