An input port of an add/drop node receives a plurality of optical
channels. An add/drop port transmits a first drop channel of the
plurality of channels when in a first channel mode and a second drop
channel of the plurality of optical channels during a second channel
mode. When the add/drop node is tuned from the first channel to the
second channel, the output port transmits the plurality of channels
spectrally located between the first channel and the second channel.