REMOTE CO2 OPTICAL-FIBER SENSOR BY MOLECU LAR ABSORPTION AT 4.3 MU-M

This paper describes a remote optical fibre sensor for the carbon diox ide detection by molecular absorption in the near infrared (4.3 mu m) corresponding to fundamental mode nu(3). To overcome the problem of th e strong attenuation signal of optical fibre in the near infrared, we have used the opto-suppling technique which changes the working wavele ngth from 4.3 mu m to 860 nm and permits the use of standard optical f ibre 50/125. The simulation of absorption has been obtained by origina l modelisation of the absorption spectrum and the establishment of the calibration curves takes to the sensor to detect a partial pressures greater than 100 mu bar with a minimal error margin of 100 mu bar, whi ch is acceptable considering the future use of the device. The sensor has been designed to monitor the CO2 rate in enriched greenhouses.