An optical fiber gas sensor based on harmonic detection

Principle of absorption spectrum optical fiber gas sensor was introduced. Mathematical model of optical fiber gas sensor based on difference-harmonic detection was presented and analyzed, and structure of the sensor was designed. Using the difference between referenced light intensity to metrical light intensity, we can counteract the fundamental wave component. Detecting 2nd harmonic of difference signal, we can obtain the gas concentration. By using this method, system´s ability of detecting 2nd harmonic component is enhanced, and system´s resolving power is increased too. Experimental results show that optical fiber gas sensor based on difference and harmonic detection has good detection effects.