Optical Protection Switching for Single Fibre Bidirectional WDM Optical Ring

Optical protection switching apparatus for a single fibre bidirectional wavelength division multiplexing, WDM, optical ring, the apparatus comprising:

• first and second ports for coupling to respective first and second adjacent portions of a single fibre bidirectional WDM optical ring;
• an optical splitter comprising an input configured to receive a WDM aggregate optical signal, a first output coupled to the first port and a second output coupled to the second port;
• an optical switch coupled between the second output and the second port;
• and
• processing circuitry configured to receive at least one of an indication of transmission continuity in the optical ring and an indication of transmission discontinuity in the optical ring, and configured to generate a switch control signal comprising instructions to cause the optical switch to be open when there is transmission continuity in the optical ring or comprising instructions to cause the optical switch to be closed when there is transmission discontinuity in the optical ring.