add_route_from_corners builds a route that passes through a list of explicit corner points, given in absolute coordinates (database units — typically 1 nm). Reach for it when you want full control over the route shape — for example, to keep a waveguide inside a routing channel, match a specific floorplan, or reproduce a hand-drawn path.

This is optical routing: bends are bend_euler at the PDK minimum radius (5 µm for cspdk.si220.cband), so the curvature is continuous at each joint and the mode mismatch stays inside the loss budget.

Imports

import doroutes as dr
import gdsfactory as gf
from cspdk.si220.cband import PDK

PDK.activate()

Z-Detour Through Four Corners

We route from in.o2 to out.o1 through four corners. The detour goes east, then up, then back west, then down to the destination — the kind of shape you'd write when the floorplan needs the route to backtrack around an obstacle or stay inside a defined channel.

dr.types.validate_position(port) extracts (x, y) in dbu from a port handle, which is what add_route_from_corners expects for start / stop / corners.

c = gf.Component()
ref = c << dr.pcells.field1()

start = dr.types.validate_position(ref.cell.insts["in"].ports["o2"])
stop = dr.types.validate_position(ref.cell.insts["out"].ports["o1"])

# Corners are absolute (x, y) points in dbu. Field1 is 50×50 µm
# (50 000 dbu on a 1 nm grid).
corners = [
    (44000, start[1]),  # head east at the input y
    (44000, 35000),  # turn north
    (1000, 35000),  # turn west
    (1000, stop[1]),  # turn south to the output y
]

dr.add_route_from_corners(
    c=c,
    start=start,
    stop=stop,
    corners=corners,
    straight="straight",
    bend={"component": "bend_euler", "settings": {"radius": 5}},
)
dr.util.show_cell(c)

Next steps

• If you'd rather describe the route as a sequence of relative moves (reusable across placements), see Steps Routing.
• The bundle (N-wire) version of this routing style is [add_bundle_from_corners][doroutes.add_bundle_from_corners], demonstrated in Array Routing.
• Don't want to spell the corners out yourself? Let A* find them in A* Single Route.