Protection switching in bidirectional WDM optical communication networks

A bidirectional wavelength division multiplexed optical communication network having a protection switching capability within a bidirectional optical waveguide comprising:

• a bidirectional optical waveguide configured to carry counterpropagating wavelength division multiplexed optical communication signals, each wavelength division multiplexed optical communication signal comprising plural optical channels;
• plural optical nodes for selectively adding and/or dropping optical channels to and/or from the bidirectional optical waveguide, the optical nodes including a first set of optical transmitters distributed among the nodes for creating M+N work optical channels in which the M channels propagate in a first direction along the bidirectional optical waveguide and the N optical channels propagate in a second, opposite direction along the bidirectional optical waveguide, where M and N are whole numbers greater than or equal to 2, the plurality of optical nodes further comprising a second set of optical transmitters distributed among the nodes, the second set of optical transmitters being capable of generating X+Y protect optical channels in which the X optical channels are configured to propagate in the first direction and the Y optical channels are configured to propagate in the second direction;
• means for detecting loss of an optical signal at an optical node;
• means for switching work optical channels to protect optical channels such that a work optical channel from the set of M optical channels is switched to a protect optical channel from the set of Y optical channels and a work optical channel from the set of N optical channels is switched to a protect optical channel from the set of X optical channels.