A bi-directional wavelength division multiplexing self-healing optical ring network is disclosed, in which N optical signals are processed at both first and second ring network so that a protection switch mechanism is performed when a link failure occurs in any one of the first and second ring networks. Various faults in the network can thus be readily identified, and appropriate tasks for modifying the network in response to the fault can be carried out. The yielding means applies a force to keep the upper paddle sealed to prevent cold air in a cold air inlet from entering a mixing zone and the lower paddle moves away from a shared sealing boundary over a predetermined angle of rotation before the upper paddle initially moves to allow cold air to enter the mixing zone. Also methods of use assembly are described.