Launching condition effect on CMC detecting optical fiber sensor based on the adsorption effect

In this paper an optical fiber sensor for detection of critical micelle concentration (CMC) is described. The sensor is based on evanescent wave phenomenon. The evanescent wave interacts with modules approaching the interface of the core cladding from the cladding side. When surfactant molecules adsorb onto the sensing region of the fiber, the optical output increases. When the concentration of surfactant solution reaches CMC and surfactants adsorb uniformly onto the sensing region, the output of the fiber increases abruptly. With the use of this phenomenon the sensor is able to detect the CMC of surfactant solution in real time instead of other methods , such as surface tension and electrical conductivity. In this paper the effect of launching condition of the light and interaction length of the sensing region on sensor sensitivity is described and it has been shown that selective rays launching and long interaction length of the sensing region improved the sensor sensitivity (Authors)