The OS-4221 is an optical path protection switch,
providing a self healing network.
This optic switch detects loss
of optical power in the primary optical path and automatically switches to the secondary (backup)
path. When the primary link is restored, the network path is restored
to the primary path. The optical protection switch can be controlled via three
methods; front panel manual switch, remote control signal, or the automatic
internal monitoring circuitry.
The optical path through the units is purely optical;
i.e. there is no optical to electrical to optical conversion. So there
is no electrical loss or electrical bandwidth limit on the fiber optic path.
Applications include telecom, datacom, ATM, and CATV systems.