Characterization of Recirculating Waveguide Meshes Based on an Optimization Method with a Parameter Space Reduction Technology

TL;DR

This paper introduces an optimization-based characterization method for recirculating waveguide meshes in programmable photonic circuits, enabling detailed imperfection analysis and improved modeling despite fabrication errors.

Contribution

It presents a novel parameter space reduction technique for characterizing individual component imperfections in complex waveguide meshes.

Findings

Successfully predicted mesh behavior with fabrication errors

Validated method on six different FIR/IRR filters

Demonstrated robustness under various practical scenarios

Abstract

Fabrication imperfections must be considered during configuration to ensure that the setup is suitable for the actual fabricated programmable photonic integrated circuits (PPICs). Therefore, characterization of imperfections is crucial but difficult, especially for PPICs made from recirculating waveguide meshes. The flexibility required by these meshes demands a more complex topology and compact TBU structure, complicating the characterization. In this paper, we propose a characterization method applicable to recirculating waveguide meshes based on an optimization approach, along with a step-by-step procedure to reduce the parameter space of optimization, allowing for characterizing imperfect parameters of each individual component within the waveguide mesh. To the best of our knowledge, this method can greatly broaden the range of characterized parameters compared to currently reported methods. In order to verify the effectiveness of our method, we used the characterized parameters to build a multi-frequency model of a mesh with fabrication errors and successfully demonstrated accurate prediction of its behavior. Furthermore, we applied our method on implementations of 6 different kind of FIR/IRR filters, to further prove the effectiveness of our method in configuring applications on meshes with fabrication errors. At last, our method was carried out under various scenarios considering beam splitter splitting ratio variance, inaccurate measurements of mesh and imprecise TBU insertion loss characterization, to demonstrate its strong robustness under various practical scenarios.