부산대학교 도서관

In this letter, we present the design of two-cascaded cavities, used as sensing head, for improving the performance of a fiber refractometer. The sensing system makes use of the Coherent-OFDR technique. Using the proposed method, only 15 % length of the sensing signal is used to calculate the refractive index (RI) of the sample under test. Due to reduction of the scanning range used for RI calculation, the nonlinearity effect in wavelength scanning is also reduced. In order to optimize the length of the sensing signal, the proposed design considers the ratio of length of each cavity. We describe, step-by-step, the design parameters; and the experiments to demonstrate the effectiveness of the proposed method. In the experiments, a resolution of 10 −6 is reported.