An optical network includes an optical ring having a plurality of subnets.
The subnets each include one or more add/drop nodes that are coupled to
the optical ring and that passively add and drop traffic to and from the
optical ring in one or more wavelengths. The optical network also
includes a plurality of gateway nodes that are each coupled to the
optical ring at a boundary between neighboring subnets. Each gateway node
forwards a first copy of a received optical signal to a
multiplexer/demultiplexer unit of the gateway node, which selectively
forwards or terminates the traffic in each wavelength of the first copy.
The gateway nodes also forward a second copy of the received optical
signal to a regeneration element. The gateway nodes selectively forward
or terminate the traffic in each wavelength of the first copy at the
multiplexer/demultiplexer unit. Moreover the gateway nodes selectively
perform one of the following on the traffic in each wavelength of the
second copy at the regeneration element: terminate the traffic, forward
the traffic after regenerating the traffic, or forward the traffic after
regenerating and converting the wavelength of the traffic.