Optical Fiber CO Sensor Research On Transmission Gas Cell

Carbon monoxide(CO) is a kind of colorless, odorless, and highly toxic gas. A gas leakage in the home and industrial production are particularly easy to be overlooked and lead poisoning, and severe cases may cause death. Therefore, in order to ensure the safety of people's lives and industrial production, we need to be able to quickly and accurately detect the CO gas concentration, by which accidents can be detected so that we can safely and quickly evacuate before the CO concentration arrive the dangerous level.There are many shortcomings by the traditional detection methods, such as poor stability, low sensitivity, short life, and cannot be adapted to the harsh environment. The spectral absorption optical fiber sensor mainly uses the light to detect the gas, therefore it may be more suitable for harsh environment in industrial complex detection and has a good prospects.This article presents the solution of harmonic detection after difference detection. In order to effectively eliminate the interference of instability factor and highly improve the detection sensitivity and SNR. This paper put forward the overall design of the sensor.Mathematical model of transmission type of gas cell that based on cascaded GRIN Lens couples was analyzed. This design solves the coupling problem between the optical fiber and fragmented optical elements. The PIN can be directly connected to the end of optical fiber. There is rarely transmission loss and it will not be affected by electromagnetism, which can be used in harsh environment and is suitable for long-distance transmission. At the same time, the lens connected in series, without increasing the length of the gas chamber lengthened absorption path length, making the detection accuracy is greatly increased.To weak signal detection section, firstly, the resultant signal after differential detection and the “pure” reference signal input phase sensitive detector together. Using the principle of useful signal and noise uncorrelated to filter noise and extract the useful signal.Finally, based on the theoretical analysis, complete experiments of the optical fiber sensor co concentration detection and verify the feasibility of the experiment scheme.