Polarization Mode Coupling Involved in a Capillary Optical Fiber Sensor: Modeling and Experimental Validation

Theoretical and experimental work is reported on a distributed polarimetric fiber optic sensor designed for application in capillary gas chromatography. The emphasis is made on the modeling of the polarization mode coupling mechanism in relation to the vapor zone distribution. Conditions are established to quantify the vapors´ amount in the capillary from a Fourier analysis of the time-modulated optical signal. The model predicts an exponential temporal decay of the modulation amplitude for any initial vapor zone distribution at the injection and the quantification is related to the pre-exponential factor.