Monitoring changes in the refractive index of gases by means of a fiber optic Fabry-Perot interferometer sensor

We have developed a simple fiber optic Fabry-Perot interferometer (FPI) sensor that is used to precisely monitor changes in the refractive index of gases. The operating principle of the sensor is discussed in this paper, and it was noticed that the wavelength positions of the FPI reflectance peaks change linearly with the refractive index of gases. Using this unique property of FPI sensors, it is feasible to achieve a resolution of better than 10−5 in monitoring the changes in the refractive index of gases. The sensor has been successfully used to monitor changes in the refractive index of nitrogen gas as a function of pressure.