Systems and methods use single-fiber optical add/drop multiplexers (OADMs)
to enable bi-directional data transmission in WDM systems over a single
fiber. By reducing the required capacity for an optical network from dual
fibers to a single fiber, significant cost and bandwidth efficiencies are
achieved. The systems and methods also provide redundancy protection in
single-fiber bidirectional line ring systems. In the event of a
downstream fiber or device failure, the OADM module receives a signal on
a first wavelength from a first direction, shifts the signal from the
first wavelength to a second wavelength, and sends the signal back down
the fiber it originated from on the second wavelength, thus maintaining
the propagation of the signal in the ring system.