OS-7121 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 switch also contains a transmitter splitter for
creating the redundant transmit path.
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.