Fiber Optic Connector Types: Shapes and Polish Codes
The connector determines whether two cables can meet at all, and the polish on the ferrule determines how much light is reflected back. Both must match.
Quick Answer
| Connector | Latch type | Typical use | Size |
|---|---|---|---|
| LC | Small form factor, push pull | Patch panels, high density | Smallest common |
| SC | Square, push pull | Telecoms, older panels | Medium |
| ST | Bayonet twist | Legacy multimode | Medium |
| FC | Screw | Test equipment, industrial | Medium |
| MPO or MTP | Multi fibre push pull | Data centre trunk cables | Carries several fibers |
Polish Codes Explained
PC
Physical contact, slightly domed ferrule. Basic grade.
UPC
Ultra physical contact, better return loss. Usually blue body on single mode and beige or grey on multimode.
APC
Angled physical contact, the end face is cut at an angle. Lowest back reflection, usually green. Never mate APC to UPC, since the angles do not match and the connection will be lossy and possibly damaging.
Colour codes
Blue for UPC single mode, green for APC single mode, aqua for OM3 and OM4 multimode, violet for OM4 in some conventions, orange for OM1 and OM2.
Choosing Correctly
- Identify the connector on the existing equipment.
- Check the polish code, not only the connector shape.
- Decide simplex or duplex, depending on the transceiver.
- Match the fiber type, single mode or multimode.
- Check the boot style for the panel or tray you are using.
Real-World Applications
- Patch cords between panels and switches.
- Test leads for optical power measurement.
- Data centre trunk links with multi fibre connectors.
- Industrial links with screw coupling connectors.
Related Guides
For fiber types, read single mode vs multimode fiber. For the basics, see what is fiber optic cable.
FAQ
Can I join LC to SC?
Yes, with a hybrid patch cord or an adapter. The fiber type and polish must still match.
What happens if I mix APC and UPC?
High loss and possible connector damage. They are not compatible.
Which connector is best for patch panels?
LC for density, since it is the smallest common connector and allows duplex pairs in a small footprint.
How do I read the colour?
Green indicates angled single mode, blue single mode, aqua or violet multimode, orange legacy multimode.