Resolving accuracy-resolution trade-off in FBG via bidirectionally symmetric input AWG combined with the CoG algorithm

This paper proposes a bidirectional symmetric input arrayed waveguide grating (AWG) architecture based on multimode interference (MMI), fabricated on a silicon-on-insulator (SOI) platform using a double-etching process. Through systematic comparison of two AWGs designs, two interrogation strategies, and two algorithms, this study elucidates the fundamental relationships between design parameters, device characteristics, and interrogation performance. The developed 2 × 12-channel interrogation chip achieves insertion loss <6 dB, 3-dB bandwidth of 1.467 nm, and crosstalk < -22.9 dB. Experimental results demonstrate 3.94 pm accuracy at 2 pm resolution with excellent temperature stability, effectively overcoming the trade-off between accuracy and resolution for high-performance FBG interrogation applications, offering a viable approach for high-performance FBG interrogation systems.