A hot-pluggable transceiver module snaps into a cage on a switch, router, or optical line terminal so the port’s medium can be chosen separately from the chassis.
One cage can take a fiber module or a copper module. The module converts between the equipment’s electrical signal and the cable. Modules are sold for different speeds, so the rate belongs to the module you seat, not to one fixed speed of the cage.
How the Cage and Module Fit
- Cage: A socket on the face of the switch, router, or optical line terminal. The host’s electrical contacts meet the module when it is fully seated.
- Hot Swap: The module can be removed and replaced while the chassis stays powered. A change of cable type does not require taking the equipment down.
- Separate Medium: Fiber or copper is a choice of module. The cage and the rest of the chassis stay put.
Fiber and Copper in One Slot
The host still presents an electrical signal to the cage. A fiber module turns that signal into light on fiber and turns incoming light back into an electrical signal. A copper module keeps the path electrical and drives a copper cable. Either module occupies the same cage.
| Choice | What Changes |
| Fiber module | The cable side is light on fiber. The host side remains the equipment’s electrical signal. |
| Copper module | The cable side stays electrical on a copper cable. The same cage accepts it. |
| Speed | Modules are sold for different speeds. The seated module, the port, and the far end have to share a speed they all support. |
What Stays the Same When the Module Changes
The chassis, the cage, and the act of seating a module stay the same. What you change is the medium and the speed that particular module was built for. A module made for a higher speed still needs a port that can run it, and the device at the other end of the cable has to match.