Fig. 1. Schematic of a MPS-ISFBG structure

Fig. 2. ISFBG filter with two insertedπphase shifts

Fig. 3. The relationship between the 3 dB bandwidth and shape factor of ISFBG in different factors

Fig. 4. Transmission channel of the central frequency at 193.10 THz

Fig. 5. ISFBG filter with three insertedπphase shifts

Fig. 6. ISFBG filter with multiple insertedπphase shifts and threeπphase shifts structure

Fig. 7. Transmission channel of central frequency at 193.100 THz