Fiber optic patch cables come with different connector types on the ends, and picking the wrong one means the cable simply will not plug in. The three you will see most often are LC, SC and ST. Here is how they differ and which one you need.
The short answer
- LC: small, push-latch connector. Fits SFP/SFP+/QSFP transceivers on modern switches, routers and NICs.
- SC: larger, square push-pull connector. Common on patch panels, media converters and fiber-to-the-home equipment.
- ST: round, twist-lock bayonet connector. Found on older and industrial equipment.
Side-by-side comparison
| Feature | LC | SC | ST |
|---|---|---|---|
| Ferrule size | 1.25 mm | 2.5 mm | 2.5 mm |
| Locking style | Push-latch (like an RJ45 clip) | Push-pull | Twist bayonet |
| Size | Small, high density | Medium, square | Medium, round |
| Typical use | Data centers, SFP modules, modern switches | Patch panels, media converters, telecom, FTTH | Legacy networks, industrial and some campus gear |
| Common today? | Yes, the standard for new equipment | Yes, in panels and telecom | Declining, mostly legacy |
LC (Lucent Connector)
LC uses a 1.25 mm ferrule, half the size of SC and ST, so you can fit twice as many ports in the same space. That is why it became the standard for SFP, SFP+, SFP28 and QSFP optics. It clicks in with a small latch, similar to an Ethernet plug. If you are connecting to a current switch or server NIC, you almost certainly need LC on at least one end.
SC (Subscriber Connector)
SC is a square, snap-in connector with a push-pull design. It is easy to plug and unplug by hand and is very common on older patch panels, media converters, optical network terminals (ONTs) and telecom equipment.
ST (Straight Tip)
ST has a round body with a twist-and-lock bayonet, similar to a BNC coaxial connector. It was widely used in early multimode networks and is still found in industrial settings and legacy patch panels. For new installs, LC or SC is usually the better choice.
Duplex vs simplex
Most fiber links need two strands, one to transmit and one to receive, so patch cables are usually duplex (two connectors per end, clipped together). Simplex cables have a single strand and are used with single-fiber (BiDi) optics and some media converters.
Mixed connectors: LC-SC, LC-ST and more
Mixed networks are normal. A new switch with LC ports connected to an older SC patch panel needs an LC-SC cable. A legacy ST panel needs an LC-ST or SC-ST cable. Patch cables come in every combination, so look at the port or panel at each end and match them.
UPC vs APC polish
Connector end-faces come with two common polish types:
- UPC (Ultra Physical Contact): flat-ish polish, usually blue connector body for single-mode. Standard for most data networking.
- APC (Angled Physical Contact): 8-degree angled polish, usually green connector body. Reduces back-reflection and is common in FTTH, CATV and some telecom links.
Do not mix UPC and APC. The different end-face angles do not mate properly, which causes high loss and can damage the connector. Check what your equipment uses.
Connector and fiber type must both match
The connector is only half of the decision. You also need to pick the fiber type (multimode OM3/OM4 or single-mode OS2) that matches your transceivers. Read our guide: OM3 vs OM4 vs OS2: How to Choose the Right Fiber Optic Patch Cable.
Handling and cleaning tips
- Keep dust caps on until you plug in. Dirty end-faces are the most common cause of fiber link problems.
- Clean connectors with a lint-free wipe or a fiber cleaning pen if a link is unstable.
- Never look into a live fiber or transceiver. Invisible laser light can harm your eyes.
- Avoid tight bends. Follow the cable's minimum bend radius to prevent signal loss or breakage.
Frequently asked questions
Which fiber connector is most common?
LC is the most common for new data networking equipment. SC is still widely used in patch panels, media converters and telecom gear.
Can I use an adapter to convert LC to SC?
Yes, LC-to-SC adapters (couplers) exist and work if the fiber type matches. An adapter adds a small amount of insertion loss, so a direct LC-SC patch cable is usually cleaner.
Is ST better than SC or LC?
No. ST is an older design. It still works well but is mainly used to match legacy equipment.
How do I know which connector my device uses?
Check the transceiver or device manual, or look at the port. Small push-latch ports are LC, larger square ports are SC, and round twist-lock ports are ST.
Browse our fiber optic cable collection for LC, SC and ST patch cables, or contact us and we will help you match the right cable to your equipment.