Fig. 1. Structure of series-parallel WDM fiber Bragg grating sensor network

Fig. 2. Overlapping types of FBG reflection spectra. (a) Non-overlapping; (b) partly-overlapping; (c) fully-overlapping

Fig. 3. Wavelength demodulation architecture of GRU model

Fig. 4. Unit structure of GRU network

Fig. 5. Training process of GRU model

Fig. 6. Three typical cases of overlapping spectral wavelength detection. (a) Non-overlapping; (b) partly-overlapping; (c) fully-overlapping

Fig. 7. Effect of training samples on detection performance

Fig. 8. Effect of batch size on detection performance

Fig. 9. Effect of numbers of GRU hidden units on detection performance

Fig. 10. Cumulative probability distribution of RMS for different methods