I. Introduction
Silicon-On-Insulator (SOI) has become a major platform for integrated photonic circuits. The ultra-high index contrast allows for extremely compact optical components, while the compatibility with CMOS processing technology brings large-scale and low-cost fabrication on the table. Sub-micron waveguides are definitely the most important and extensively used building block in a circuit, but their detailed behavior is often somewhat ignored. In most cases, the waveguide is simply modelled with a wavelength-independent propagation loss plus a linear dispersion. Yet in reality, a waveguide has unavoidable and performance-limiting imperfections.