[57] ABSTRACT A communications network has a plurality of nodes inter connected by an
optical transmission medium. The trans mission medium is capable of a carrying a plurality …

An add/drop multiplexer/demultiplexer (ADM) for Switching, modulating and attenuating
optical Signals in a fiber optic network employing wavelength division multi plexing (WDM) …

In conventional ring-type optical networks, loop-back techniques have been employed to
recover from a fiber or node failure. The principle of the loop-back techniques is illustrated in …

An optical wavelength multiplexing and demultiplexing device may transmit an optical signal
equivalent to a lost optical signal on a normal section in WDM network. The optical …

BACKGROUND Wavelength Division Multiplexing (WDM) optical net Works have
traditionally been used for long haul point-to point transmission. However, with the …

An arrangement for the implementation of an add/drop method in optical signals transmitted
wavelength-division multiplex in which an interferometer includes a divider for generating …

Accordingly, it is an object of the invention to provide a pass-monitoring apparatus of an
optical network System, which can be Suitably used in the optical network System …

In a loop network system, a method and apparatus for automatic bypass of a node port
associated with a hub port when the node port generates a number of errors beyond a …