MZI-switched dual-input SOI-AWG interrogator for neural-network-assisted FBG interrogation.

Abstract

A dual-input silicon-on-insulator (SOI) arrayed waveguide grating (AWG) fiber Bragg grating (FBG) interrogator, enabled by an on-chip Mach-Zehnder interferometer (MZI) switch, is proposed and experimentally demonstrated. The device integrates a polarization beam splitter (PBS), a thermo-optic MZI, and an asymmetric dual-input AWG. The MZI enables on-chip selection of two AWG input ports, generating complementary spectral responses without increasing the number of output channels. Due to fabrication-induced non-idealities in SOI-AWG responses, conventional fitting-based interrogation methods suffer from increased errors. A feature-engineered feedforward neural network (FNN) is developed by exploiting multichannel responses from the two input states. Experimental results show that the proposed dual-input FNN achieves an interrogation root-mean-square error (RMSE) of 2.33 pm on an independent external test set, reducing the error from 8.06 pm obtained by polynomial fitting. This work provides a compact and high-precision solution for on-chip FBG interrogation.