Crosstalk Reduction and Demodulation Stability Promotion in Inline Fiber Fabry–Pérot Sensor Array Using Phase Generated Carrier Scheme

An inline time-division multiplexing (TDM) fiber Fabry-Pérot sensor array based on the low-reflectivity fiber Bragg gratings (FBGs) is promising for lots of sensing applications. The intrinsic multireflection (MR) between the FBGs with the same Bragg wavelength is a serious problem, which induces crosstalk and generates false detection information. Furthermore, the amplitude of the demodulated signal cannot reach a stable state due to the MR. Here, we presented a full theoretical demonstration of the MR-induced crosstalk fluctuation and demodulation instability, where the phase generated carrier method was used as the interrogation scheme. An interference synthesis method was presented to reduce the MR-induced crosstalk and to promote the demodulation stability simultaneously. The experimental results showed that a crosstalk reduction of 18 dB and a demodulation stability promotion of 1.42 dB could be achieved with the FBG reflectivity of 5%. The principle of the method can be extended to the array with more TDM channels.