  We report a novel process variation-aware compact model of strip waveguides
that is suitable for circuit-level simulation of waveguide-based process design
kit (PDK) elements. The model is shown to describe both loss and -- using a
novel expression for the thermo-optic effect in high index contrast materials
-- the thermo-optic behavior of strip waveguides. A novel group extraction
method enables modeling the effective index's ($n_{\mathrm{eff}}$) sensitivity
to local process variations without the presumption of variation source. Use of
Euler-bend Mach-Zehnder interferometers (MZIs) fabricated in a 300~mm wafer run
allow model parameter extraction at widths up to 2.5~$\mu$m (highly multi-mode)
with strong suppression of higher-order mode excitation. Experimental results
prove the reported model can self-consistently describe waveguide phase, loss,
and thermo-optic behavior across all measured devices over an unprecedented
range of optical bandwidth, waveguide widths, and temperatures.
