Routing automation between components ports

fp.Linked, a functional module for port routing automation, is included in PhotoCAD. This module automates the routing of components in a layout by defining port connections in a Python script. For ports that require waveguide transition, the tool automatically selects the appropriate waveguide transition unit to convert the different waveguide types. After running the script file, a local folder is created to store the generated GDS, netlist, etc.

Linked

Linked, a functional module for port routing automation, is included in PhotoCAD. This module automates the routing of devices in a layout by defining port linking relationships in a Python script. For ports that require waveguide transition, the tool automatically selects the appropriate waveguide transition unit to convert the different waveguide types. After running the script file, a local folder is created to store the generated GDS, netlist, etc.

This example uses a script to place several different types of waveguides, set the connection relationship between waveguide ports, and achieve automatic routing of different types of waveguides through Linked in PhotoCAD.

Full Script

Section Script Description

Import the functional modules and the gpdk package:

from fnpcell import all as fp
from gpdk import all as pdk
from gpdk.technology import get_technology
from gpdk.technology.waveguide_factory import EulerBendFactory

Define class Linked:
```
class Linked(fp.PCell):
```

Define build function to generate components

Parameters correspond to instances, graphics, and ports in the function module:
```
def build(self):
    insts, elems, ports = super().build()
```
Implemented the waveguide used to connect the component ports in the function using the get_technology() module in gpdk:
```
TECH = get_technology()
```
The SBend module in gpdk creates an S-shaped bend which is an Euler Bend, where parameters such as distance, height, waveguide_type and bend_factory control the lateral distance of the two ports, the vertical distance of the two ports, waveguide type and the process of the bend, respectively. Parameters such as radius_min, l_max and waveguide_type control the process of the generated EulerBend:
```
sbend = pdk.SBend(distance=100, height=-90, waveguide_type=TECH.WG.FWG.C.WIRE, bend_factory=EulerBendFactory(radius_min=15, l_max=35, waveguide_type=TECH.WG.FWG.C.WIRE))
```

Define four different types of straight waveguides through the Straight module in gpdk, with the parameters length and waveguide_type controlling the length and type of the straight waveguide, respectively:

straight_fw = pdk.Straight(length=5, waveguide_type=TECH.WG.FWG.C.WIRE)
straight_fe = pdk.Straight(length=5, waveguide_type=TECH.WG.FWG.C.EXPANDED)
straight_mw = pdk.Straight(length=5, waveguide_type=TECH.WG.MWG.C.WIRE)
straight_sw = pdk.Straight(length=5, waveguide_type=TECH.WG.SWG.C.WIRE)

Create six different devices from each of the four different types of waveguides defined below, and control the position of the device by the translated(x,y) method; control the rotation angle of the device by the rotated(degrees=n) method

sb10 = sbend.translated(-200, 0)
s10 = straight_fw
s15 = straight_fe.translated(100, 0)
s20 = straight_sw.translated(200, 0)
s30 = straight_mw.rotated(degrees=30).translated(300, 100)
s40 = straight_fw.rotated(degrees=30).translated(50, 100)

Define the connection relationship between the ports by calling the fp.Linked module to achieve automatic routing and combine all waveguides used for device port connection as device. For example, sb10["op_1"] <= s10["op_0"] defines that the op_0 port of device s10 is connected to the op_1 port of sb10. The completed device has only two ports, op_0 of sb10 and op_1 of s40:

device = fp.Linked(
    link_type=TECH.WG.SWG.C.EXPANDED,
    bend_factory=TECH.WG.FWG.C.WIRE.BEND_EULER, #bend_factory,
    links=[
        sb10["op_1"] >> s10["op_0"],
        s10["op_1"] >> s15["op_0"],
        s15["op_1"] >> s20["op_0"],
        s20["op_1"] >> s30["op_0"],
        s30["op_1"] >> s40["op_0"],
    ],
    ports=[sb10["op_0"], s40["op_1"]],
)

Instantiate device:
```
insts += device
```
Returns the instance, element and port of the generated device:
```
return insts, elems, ports
```

Create layout units using class Linked:

if __name__ == "__main__":
    from gpdk.util.path import local_output_file

    gds_file = local_output_file(__file__).with_suffix(".gds")
    library = fp.Library()

    TECH = get_technology()
    # =============================================================
    # fmt: off

    library += Linked()

    # fmt: on
    # =============================================================
    fp.export_gds(library, file=gds_file)
    # fp.plot(library)

Export GDS Layout
1. - Linked: Top Level Layout Unit
  - Linked_x1: Subunits of Linked, containing Linked_links and other component modules.
  - Linked_links：Automatically generated combinations of waveguides connecting ports of various types of components.
  - SBend: Eulerbend of the generated S-shape defined in the script.
  - Straight*: Define the generated Straight waveguide in the script.
2. The Linked_links in the Cells list is a collection of waveguides automatically generated under the Linked function. Double-click on the Linked_links to hide them, and you can see in the layout the S-shaped EulerBend and the five straight waveguide shapes placed by the script, whose positions are realized in the script by .translate().
3. Double-click Linked_links again to display it, and you can see that the connection waveguide generated by the script is adapted according to the port waveguide type, and the bend is automatically selected according to the port direction and angle to adjust the waveguide direction.

AutoTransitioned

In the case that the device ports need to connect to different types of waveguides, the AutoTransitioned method can be used to implement the transition of the component ports, and the specific schematic of this function is given in gpdk > routing > auto_transitioned > auto_transitioned.py, and the core usage is as follows

if __name__ == "__main__":
    from gpdk.util.path import local_output_file

    gds_file = local_output_file(__file__).with_suffix(".gds")
    library = fp.Library()

    TECH = get_technology()
    # =============================================================
    # fmt: off
    from gpdk.components.mmi.mmi import Mmi

    library += AutoTransitioned(device=Mmi(waveguide_type=TECH.WG.FWG.C.WIRE), waveguide_types={"*": TECH.WG.SWG.C.WIRE})

    # fmt: on
    # =============================================================
    fp.export_gds(library, file=gds_file)
    # fp.plot(library)

Here, different waveguide types of component ports are connected by using the AutoTransitioned class, where the parameter device is used to receive the components whose ports need to be automatically converted; waveguide_types receives the waveguide types of the converted ports, where *: TECH.WG.SWG.C.WIRE is a key-value pair and * refers to all undefined ports. Finally we can get the following device after port auto-transition.