Method for reducing the influence of crosstalk on quasi-distributed sensing network with time-division multiplexing fibre Bragg gratings

Abstract

Abstract A serial time-division multiplexing (TDM) quasi-distributed sensing array based on the ultra-weak reflection fibre Bragg gratings (FBGs) has been widely used in various areas. However, multiple reflections and shadow effect between FBGs with the same centre wavelength will accumulate as the number of gratings multiplexed increases, which will cause a significant increase in crosstalk of the reflection spectrum and will seriously affect the accuracy of the measurement results. In this paper, we theoretically analyse the instability of the results caused by multiple reflections and shadow effect, and propose a layer-by-layer compensation method to suppress crosstalk and improve the stability of the results. About 4000 FBGs with a reflectivity of 0.01% were multiplexed in the experimental system, and we measured the fluctuation of the centre wavelength of the grating at different distances to prove the effectiveness of the method we proposed. The experimental results show that the method proposed in this paper can greatly reduce the shift of the centre wavelength of the reflection spectrum and improve the stability of the system.