Routing into these two types of systems involves routing an RF signal into two possible types of components:
- An SMA connector, preferrably a vertical connector
- An SFP, XFP, or similar connector for the optical module
SMA connectors require a wideband signal transition that can provide the required bandwidth. Generally, routing with a coplanar waveguide structure on the outer layers of the PCB will be sufficient to reach into the connector with low return loss up to 10's of GHz as long as there are no via transitions.
An example of this type of wideband signal transition using a blind via is shown below (area circled in yellow). The footprint used here includes a small array of blind stitching vias to set the via transition impedance to a target value.
For routing into the SFP/XFP or similar connector for an optical module, follow the same strategies you would normally follow with digital channels running at high Gbps data rates. This is because those lines will be able to handle broad bandwidths associated with digital signals, so they will not have a problem also handling high-frequency RF signals.