For each of these connectors, there are three available options for the length type: Geometrical, Optical and Group.
- Geometrical optimizes the geometrical, physical length of the center path of the waveguide
- Optical optimizes for the integrated effective index along the waveguide
- Group optimizes for the integrated group index along the waveguide
These connectors are very useful in designing phase sensitive devices, such as an asymmetrical Mach-Zehnder interferometer and 90 degree hybrid.
For example, the asymmetric Mach-Zehnder model, shown below, combines two 50-50 MMIs with a small asymmetric delay to achieve any desired splitting ratio.