A High-Precision Wavelength Demodulation Method Based on Optical Fiber Fabry-Perot Tunable Filter

A high-precision wavelength demodulation method based on optical fiber Fabry-Perot tunable (FPT) filter is proposed for the fiber Bragg grating temperature sensing system. This algorithm uses the original sampling data obtained from the data acquisition card to simultaneously calculate the transmission spectrum of the F-P etalon (FPE) and the reflection spectrum of the fiber Bragg grating (FPG) sensors. In each scanning cycle, the transmission spectrum wavelength of the F-P etalon (FPE) is calibrated dynamically in real time, the reflectance spectrum central wavelength of the FPE sensors is calculated by referring to the transmission spectrum wavelength of the FPE that has been calibrated. It effectively weakens the perturbation effect caused by the nonlinear and non-reproducibility of narrowband light source from the fiber FPT filter, reduces the numerical error and effectively eliminates the pseudo peak of the FPE, and greatly improves the measurement accuracy of the system. Most programming languages can implement this algorithm. A temperature sensing experiment for the proposed method has been carried out. Results showed that the demodulation precision by our method could reach up to ±0.2 °C, wavelength demodulation accuracy 3 pm.