Multiple Reflections Induced Crosstalk in Inline TDM Fiber Fabry-Perot Sensor System Utilizing Phase Generated Carrier Scheme

An inline time-division multiplexing fiber Fabry-Perot (TDM-FFP) sensor system based on low-reflectivity fiber Bragg gratings (FBGs) is ideally suited to many applications. The intrinsic multiple reflections crosstalk (MRC) phenomenon in the inline TDM-FFP sensor system is a serious problem that limits the multiplexing number of sensors, which hindrances its practical applications. In this paper, a detailed analysis of the MRC in the inline TDM-FFP sensor system using phase generated carrier (PGC) scheme is reported. The equations of the interference intensity in the inline TDM-FFP sensor system with two sensors are deduced. The characteristics of the MRC are theoretically analyzed according to the equations and experimentally demonstrated. Finally, the instability of the MRC induced by random phase relationships of the sensors is analyzed using statistical method. The experimental results show that the crosstalk from the first sensor to the second sensor is ranged from 36.48 to 67.64 dB and to the third sensor is ranged from 16.02 to 60.64 dB.