Long distance remote sensing of methane gas using a 1.65 /spl mu/m DFB LD and a single mode fiber

摘要

We have developed DFB LDs for the sensing of various kinds of gases, and, the 1.65 /spl mu/m DFB LDs, which have been used for methane gas sensing, have the longest wavelength at the present stage. These LDs are packaged in butterfly modules with a thermo-electric cooler and an optical isolator for convenience of practical use. Second harmonic detection and differential absorption methods are widely used as the detection techniques, and wavelength stabilization to one of the absorption lines of a given gas is a key technique for both methods. For the wavelength stabilization a DFB LD module with a reference gas cell has been developed.