The Study Of Displacement And Curvature Sensor Based On Few-Mode Multi-Core Fiber

Fiber optics sensors have many advantages such as immune to electromagnetic interference, light weight, and corrosion resistance and so on. This kind of sensors has been widely investigated, and many kinds of sensors have been proposed.Few-mode multi-core fiber(FM-MCF) is a new type of transmission medium, which is used to satisfy the rapid growth of bandwidth. Optical signal transmission theory of FM-MCF has become a research focus in communication field. The FM-MCF has a large capacity, multi-channel in one fiber, lower nonlinear, lower mode dispersion, and several modes can propagate in one core at the same time. The FM-MCF attracts many attentions in communication field. The FM-MCF not only has a good performance of mode transmission but also can measure the physical parameters based on mode interference.A sensing system based on mode interference of few-mode multi-core fiber is investigated in this paper; a displacement and a curvature sensor have been studied in detail. The major contributions of this paper are given in the following aspects:We set up a sensing modal and analyze the sensing theory, and a detail calculation is given. The impacts to sensitivity of sensor are investigated, and the mode excited technology is also investigated in this paper.The fiber optics displacement sensor is investigated based on aforementioned theory. The sensing element is a segment of FM-MCF, and two segments single mode fiber are used as input and output. We analyze the parameters of fiber and structure parameters of sensor, which will have influence on the performance of displacement sensor. The experimental results showed that the sensitivity of this sensor is-61.18pm/?m with the displacement from 0 to 60?m, the error between the experimental results and the theoretical calculation is less than 3.9%.Because the FM-MCF contains several cores, we present a curvature sensor which is temperature-immune. The experiment results show that the temperature have no influence on the measurement of curvature. And the sensor have sensitivities as high as 137.0pm/m-1, 103.0pm/m-1, 68.0pm/m-1 and 30.8pm/m-1 under different gaps between two fiber cores with the curvature from 0 to 4.5m-1.Therefore, the experimental results were in excellent agreement with the theoretical calculation.