Theoretical and experimental study of self-reference intensity-modulated plastic fibre optic linear array displacement sensor

Abstract

A self-reference intensity-modulated plastic fibre optic displacement sensor of linear array configuration is presented in this paper. It consists of receivers categorised into two reference groups. The effect of the number of receivers in each reference group on the group and displacement ratio responses is investigated. Theoretical analysis, based on Gaussian beam model for multiple receivers at different offset distances, is presented. Simulation results that are based on the derived model are employed to study the ratio function for different reference groups. The predicted sensor performance, in terms of linear range and sensitivity, is verified by experiment. There is a very good agreement between the predicted and measured characteristics. The effects of the number of receivers in each reference group on linear operation range and sensitivity are compared and discussed. Both theoretical and experimental results show that the optimal linear array configuration is the (10,1) configuration. This configuration gives the best performance in terms of sensitivity and linear operational range and it is shown to have a linear sensitivity of 0.25mm−1 with non-linearity error of less than 2.0% (without additional nonlinear compensation) within a linear operation range of 15mm. In addition, the linear range of the optimal linear array (10,1) configuration is up to 10 times greater than existing plastic fibre configurations, and about 30 times greater than existing glass fibre configurations.