Fabrication technologies are not yet at a level where the exact phase relations between waveguides of different (or even nominally identical) lengths match the expected values to a sufficient degree. In most applications that rely on the phase of the light, devices will need to be tuned to the correct working point. Thermal tuning is the more common way to do this. The Thermo- and Electro-Optic Simulation Module quickly estimates power consumption required for a given phase shift, and optimizes the waveguide cross-section (including the heaters) for trade-offs between metal-induced loss and power efficiency.
Electro-optic effects tend to be much faster than thermo-optic effects, but they rely on specific crystalline materials. The Thermo- and Electro-Optic Simulation Module is suitable for the vast majority of cases in which the modes of the waveguides are very nearly linearly polarized.