TEMPERATURE SENSITIVITY OF AN OPTICAL-FIB ER CARBON-DIOXIDE PRESSURE SENSOR

An optical fibre sensor to measure weak partial pressures of carbon di oxide has been designed and realized. This sensor is based on direct m olecular absorption in the near infrared at 4.3 mu m. It is an extrins ic and amplitude modulation type sensor. In the lineal-region between 0 and 2000 mu bar, the calibration curve that represents the transmitt ed power versus the carbon dioxide partial pressure in air shows a sen sitivity of 20 nW/mbar with a minimum detectable pressure of 25 mu bar . This article describes a temperature sensitivity analysis for all op toelectronic components and proposes a calculation method to distingui sh two successive levels of partial pressure in a surrounding atmosphe re where the temperature can vary. The experimental results show that without using a reference signal, the maximum variation of temperature is +/-1.4 degrees C. The use of a reference signal combined with ther moelectric cooling of the photodetector tolerates a temperature variat ion of +/-25 degrees C.