jevillegasd
commented
2 years ago Waveguide crossings tool
The waveguide crossings tool allows for .... inserting waveguide crossings automatically.
- Upon calling path_2_waveguide2() if any of the selected paths intersects with one another, and a cell for a crossing has been configured in the waveguide XML file (and exists in the technology files), a user may insert a crossing cell automatically at the crossing location.
- Modifications include minor changes in path_to_waveguide, a new file in SiEPIC utils called crossings (is this the correct location??), and a change in core waveguideGIU to include the parameter 'crossing_cell' in the search for waveguide parameters. I've copied the 4crossing cell from Prof Shi (in the EBeam PDK) in the GSiP technology gds files so that the crossings functions have something to do with the generic tech by default, and modified the corresponding WAVEGUIDE.xml definition to include an example of referencing the crossing cell.
It can be tested using the attached file, to generate the other attached file: crossings.zip
Know issues
- To generate the crossing it expects that the crossing is well centered and uses the bounding box (not the DevRec bounds) to determine the size of the crossing cell, therefore it's always slightly larger than what it needs because of the pin half_length. This normally doesn't generate any problem since the waveguides themselves will snap to the new pins upon creation.... but sometimes they don't, leaving small spaces between the waveguide and the crossing cell.
- The crossing cell needs to be square and only supports manhattan waveguides. Putting a non-manhattan crossing now generates an undefined behavior (usually just cuts the waveguide in place and leaves disconnected crossings in each crossed location)
A small change in the reading part of the layer information, in the form of a recursive call to allow deeper structures in the layer deck. Tested against AMF_PDK and is working well (I think that's the only PDK library initialization that is using this function currently). Nested groups in the layer deck can with this be used to allow extra categorization. For example: