Baseband Macromodeling of Linear Photonic Circuits for Time-Domain Simulations

In this paper, we propose a novel approach to build real-valued baseband models of linear, time-invariant, passive photonic devices, circuits, and systems, which allows modeling of photonic wavelength filter circuits with their full dispersion effects in an accurate way. The proposed technique starts from the scattering parameters of the photonic systems under study and leverages on the modeling power of the vector-fitting algorithm, thereby leading to both complex- and real-valued baseband state-space models. The modeling procedure is robust and applicable to general linear passive photonic devices and circuits, and the physical properties of the resulting models for the time-domain simulation, such as stability and passivity, can be properly guaranteed. The built models are systems of first-order ordinary differential equations (ODEs), which can be efficiently simulated in a variety of ODE solvers at baseband frequencies rather than in the optical frequency range. We demonstrate the applicability and accuracy of the proposed method on two examples of photonic filter circuits.