Bidirectional WDM optical communication system with bidirectional add-drop multiplexing

An optically-amplified bidirectional optical add-drop multiplexer for optically add-dropping optical channels to and from a bidirectional optical waveguide configured to carry first and second counter-propagating wavelength division multiplexed (WDM) optical communication signals each including plural channels comprising:

• a first optical circulator for receiving a first WDM optical signal from a bidirectional optical waveguide and for placing a second, counter-propagating WDM signal onto the bidirectional waveguide, the first and second WDM optical signals each comprised of optical channels having wavelengths positioned within different gain regions of an optical amplifier;
• a first optical amplifier optically communicating with the first optical circulator such that the first WDM optical signal traverses the optical amplifier;
• a second optical circulator optically communicating with the optical amplifier for receiving the amplified first WDM optical signal through a first optical port and outputting the amplified first WDM optical signal from a second output port;
• at least one optical channel selector optical communicating with the second output port of the second optical circulator for selecting an optical channel to be dropped from the first amplified WDM optical signal and including an optical path permitting the non-selected, through optical channels from the first WDM optical signal to pass through the optical channel selector;
• means for adding one or more additional optical channels to the through optical channels of the first WDM optical signal whereby the first WDM optical signal and the one or more additional optical channels are output to the bidirectional optical waveguide;
• a third optical circulator for receiving a second WDM optical signal from a bidirectional optical waveguide and for placing the first, counter-propagating WDM signal onto the bidirectional waveguide;
• a second optical amplifier optically communicating with the third optical circulator such that the second WDM optical signal traverses the second optical amplifier;
• a fourth optical circulator optically communicating with the second optical amplifier for receiving the amplified second WDM optical signal through a first optical port and outputting the amplified second WDM optical signal from a second output port;
• at least one optical channel selector optical communicating with the second output port of the fourth optical circulator for selecting an optical channel to be dropped from the second amplified WDM optical signal and including an optical path permitting the non-selected, through optical channels from the second WDM optical signal to pass through the optical channel selector;
• means for adding one or more additional optical channels to the through optical channels of the second WDM optical signal whereby the second WDM optical signal and the one or more additional optical channels are output to the bidirectional optical waveguide via the first optical circulator.