Patent ID: 8928885
Filing Date: 2015-01-06
Classification: G01N

Abstract:
1. A gas detection system using a semiconductor laser with a gas reference cavity for compensation, said system comprising: a first light source emitting a first beam of a first wavelength as a detection beam; a second light source emitting a second beam of a second wavelength, which is different from the first wavelength, as a reference beam, the first wavelength of said detection beam is same as the characteristic absorption lines of the gas to be detected; a first wavelength division multiplexer connected with said first light source and said second light source, for combining optical signals of first and second beams of different wavelengths into one beam to output; a broadband coupler connected with said first wavelength division multiplexer, said broadband coupler is used for dividing the laser light after being combined by said first wavelength division multiplexer into a first and second output beams according a certain ratio of power; a reference gas chamber, which is introduced with reference gas of the same composition as that of the gas to be detected and of a known concentration, and receives the first output beam from said broadband coupler to make it pass through the reference gas; a detection gas chamber, which is introduced with the gas to be detected, and receives the second output beam from said broadband coupler to make it pass through the gas to be detected; a second wavelength division multiplexer connected with said reference gas chamber, for splitting the beams passing through said reference chamber according to said first wavelength and said second wavelength; a third wavelength division multiplexer connected with said detection gas chamber, for splitting the beams passing through said detection gas chamber according to said first wavelength and said second wavelength; a first photodetector connected to said second wavelength division multiplexer for receiving the split beam having the first wavelength, so as to generate a first light intensity signal; a second photodetector connected to said second wavelength division multiplexer for receiving the split beam having the second wavelength, so as to generate a second light intensity signal; a third photodetector connected to said third wavelength division multiplexer for receiving the split beam having the first wavelength, so as to generate a third light intensity signal; a fourth photodetector connected to said third wavelength division multiplexer for receiving the split beam having the second wavelength, so as to generate a fourth light intensity signal; a feedback control unit for receiving and comparing said first, second, third and fourth light intensity signals, and converting the comparison result into a feedback signal so as to adjust the output of said first light source and said second light source.