Discriminating Rayleigh backscattering induced false crosstalk in inline interferometric FBG sensor arrays.

The crosstalk between channels is a main factor restricting the performance of interferometric fiber Bragg grating (FBG) time-division and wavelength-division hybrid multiplexing arrays. The time-division crosstalk caused by multiple reflections and the wavelength-division crosstalk due to insufficient isolation are the main crosstalk problems in the Fabry-Perot (F-P) structure, seriously limiting the number of multiplexing devices and the system's applications. Many theoretical research and suppression scheme designs have been done to solve these problems. We have previously found a new crosstalk phenomenon called the false crosstalk in hybrid multiplexing arrays. This paper focuses on this phenomenon and constructs a theoretical model to analyze its causes and influencing factors. The model demonstrates the influences of Rayleigh backscattering (RB) noise and sensor position on the false crosstalk. Both theoretical and experimental results show that the false crosstalk is induced by parasitic interference in the leading fiber and changes with the leading fiber length. This study quantitatively reveals the crosstalk performance degradation with the change of sensor position in the hybrid multiplexing array and provides key support for optimizing the system array design and expanding the large-scale multiplexing capacity.