Fig. 1. Structure of tunable dual-bandpass MPF based on CFBG

Fig. 2. Output optical spectrum of MZI (Inset: detailed drawing of amplified interference spectrum)

Fig. 3. Optical spectrum after reflection by cascaded CFBG

Fig. 4. Frequency response of MPF

Fig. 5. Frequency response curves of MPF with different length differences of MZI arm

Fig. 6. Relationship curves between central frequency of dual-bandpass and length difference of MZI arms. (a) First passband; (b) second passband