(aka ST-ST Fibre Optic Cable). American spelling has been used for this write up.
ST:A certain type of end point connector for fiber optic cables. The ST classification can be best described as a central core of the fiber, with a protective coating of either condensed plastic resin or aluminum, to form a stable central connector. The actual glass fiber extends further out of this central connector, in a "soft" resin plastic connector with a tiny, exactly manufactured central hole allowing physical transmission into the firber.
Surrounding the larger central connector is a spring-loaded R-shaped cable lock connector, similar to the sheath type used on BNC/coaxial cabling. This is used to hold the connections firmly in place, allowing reliable light transfer and thus reliable transmission of information.
Advantages of the ST connector include the cheap cost to manufacture (being made of add-on materials rather than integrated components), and security of connections, since the locking connector hold the connector in place quite firmly and permanently.
Diadvantages include the ease of damage to the central soft resin plastic connector with the physical end-point. The ends can very easily snap off IN the socket that it is connected to, rendering the both the socket AND the cable useless. Considering what you are connecting to, it is a pain to extract and can potentially permanently damage the socket.
Comparable connector points include the SC-SC fiber optic cable, the RJ-45 RJ-45 fiber optic cable or a mixture of the three main connectors (i.e. ST-SC, SC-RJ45...)
The ST-ST classification indicates that both ends of the fiber optic end in the ST connector point as described above.