ST stands for Straight Tip - a quick release bayonet style Connector developed by AT&T. STs were predominant in the late 80s and early 90s.

ST Connectors are among the most commonly used Fiber optic connectors in networking applications. They are cylindrical with twist lock coupling, 2.5mm keyed ferrule. ST Connectors are used both short distance applications and long line systems. The ST connector has a bayonet mount and a long cylindrical Ferrule to hold the fiber. Because they are spring-loaded, you have to make sure they are seated properly. They are easily inserted and removed due to their design. If you experience high Light loss, try reconnecting. ST connectors come in two versions: ST and ST-II. These are keyed and spring-loaded. They are push-in and twist types. They are rated for 500 mating cycles. The typical Insertion Loss for matched ST connectors is 0.25 dB. View all Fiber Optic Connectors.