xPDK Layout basics
layer
This section allows to define a list of GDS layers. These will be written to GDS or Oasis file or OpenAccess database.A layout oriented PDK should have one or more of these therefore.
Per layer single-layer operations are available (DRC, derived), see single layer.
applayer
This section allows to define a list of applayers. These will not be written to any output, but are typically needed for supporting DRC.Per layer single-layer operations are available (DRC, derived), see single layer.
MultiLayerOps
This section is for multi-layer (GDS or app) operations. See multi layer.A basic design kit does not need this section, but when a series of (gds or app) layers exists, it is likely to be needed to describe more complex rules and define inter-layer aspects.
xsection
This defines axsection
which in EDA-design is often called a cad or design layer. In OptoDesigner this is a mcs.A layout oriented PDK should have one or more of these therefore and they are key for schematic / circuit design also, as connecting ports in a schematic should have a matching xsection.