What Does Square Connector (SC) Mean?
A square connector or standard connector (SC) is a fiber-optic cable connector that uses a push-pull latching mechanism similar to that used in common audio/video cables, which makes it very easy to connect and disconnect the cables. A single cable is used for single-direction communication; so if a full duplex mode is required, two cables and two connectors are used in tandem.
A square connector is also known as a standard connector or subscriber connector.
Techopedia Explains Square Connector (SC)
The square connector is designed to be a snap-in connector that features a 2.5-mm ferrule that is exactly the same as that used in ST connectors, which are widely used because of their excellent performance and durability. The square connector was standardized in the Telecommunications Industry Association's TIA-568-A specification but was not widely used at first because it was more expensive than the ST connector. Progress in material and manufacturing processes, however, has ensured that it is now cheaper and much more common.
The main feature of the connector is its square, or actually rectangular, shape and simple push-pull attachment motion. This shape along with its other key features ensures that the connector is easily latched into the correct position and that the snap latches ensure that it stays in place, reducing the optical loss of signals. The connector is rated for 1000 mating cycles, and the insertion loss is only 0.25 dB.