Fiber Optic Fresnel Ratio for Measurements of Liquids Refractive Index

In this project, the measurement is performed by fiber optic Fresnel ratio meter, An optical beam (526nm or 850nm ), that obtained from a laser diode is launched into a fiber. The optical beam is divided into two paths by a 1 × 3 single-mode fiber coupler. The short path serves as the probe and the long path ( reference fiber ), that is 3km in length serves as a delay time such that reflected beam from both fiber ends are time separated. The normalized probe signal is first taken in air for calibration, then in the liquid. The measured value of R is the ratio of the normalized probe signal for air and liquid. The reflection Fresnal ratio have been adopted to measure the refractive indices. The experimental results show that a good agreement with results of refractometer. In addition reflection signals from air-fiber and liquid-fiber are compered and produced change in path length interface to obtain the refractive indices for liquids.