Fig. 1. Fiber Mach-Zehnder interference system based on 3×3 coupler

Fig. 2. Flow chart of feedback control program algorithm

Fig. 3. Schematic of positive and negative feedback judgment

Fig. 4. Results of feedback control. (a)(b) Without positive and negative feedback judgment; (c)(d) with positive and negative feedback judgment

Fig. 5. Input signal

Fig. 6. Signal detected by interference system

Fig. 7. Amplitude spectrum of signal detected by interference system

Fig. 8. Frequency spectrum of signal detected by interference system