Effect of Launching Angle of Light on Critical Micelle Concentration Determination Using an Optical Fiber Sensor Based on Adsorption Effect

In this paper, an optical fiber sensor for the determination of critical micelle concentration (CMC) is described. The sensor is based on the adsorption effect. When the concentration of the surfactant solution reaches the CMC, the outputs from the fiber suddenly begin to increase due to the interaction between the evanescent wave and surfactant molecules. Using this phenomenon, the sensor is able to determine the CMC of the surfactant solution in real time. The effect of launching angle of the light and interaction length of the fiber in the sensing region on sensor sensitivity has been studied. It has been found that the selective rays launching close to the critical angle of the fiber and the long interaction length of the sensing region increase the sensor sensitivity.