LC and SC Patch Cord Guide

LC, SC and ST are the three connector types a buyer is most likely to meet in an optical installation, and the difference between them is mechanical rather than optical. All three carry the same light over the same fiber; they differ in size, in how they latch, and in where they are found. Choosing between them is a matter of matching the equipment and the plant, not of choosing a better connector in general.

LC is the small-form connector, and it is the default for modern equipment. It uses a latch like a small telephone plug, it packs two fibers into a compact duplex housing, and it appears on SFP, SFP+, XFP and QSFP28 duplex variants and on modern patch panels. A site built in the last decade is likely LC throughout, and a buyer ordering for such a site can usually assume LC at both ends. LC to LC cords are therefore the most common patch cord in current installations.

SC is the older push-pull connector, larger than LC, and it remains common in installed plant and in telecom equipment. It latches by pushing the connector body into the adapter, and it is robust and simple, which is why it survived so long. A site with older plant, or with telecom equipment, is likely to have SC panels, and a buyer connecting new LC equipment to such a plant needs a mixed cord: LC at the equipment end, SC at the panel end. Mixed cords are standard products, made for exactly that situation, and they are ordered by stating the connector at each end.

ST is the bayonet connector, found in the oldest installations. It twists and locks like a bayonet light bulb, and it appears in plant installed when optical networking was new. A site with ST panels is rare today, but it exists, and a buyer connecting to it needs a mixed cord with ST at the panel end. The same rule applies as for SC: state the connector at each end, and the cord can be confirmed as a pair.

The practical advice is short. Read the connector type off the equipment ports and the panel adapters, not off a plan or a memory, because panels are sometimes changed without the records being updated. State the connector at each end during the inquiry. Keep the dust caps on until connection, clean the end faces before mating, and never touch an end face. This guide states connector practice at category level; no patch cord model or specification is stated here as a product claim. Before ordering, confirm quantity, price and delivery time during the inquiry. Certificates are available upon request.