Finesse controllable active ring-resonator-coupled M-Z interferometer optical switches

In order to get the lowest switching power in the ring-resonator-coupled M-Z interferometer switching devices, the loss in the ring resonator has to approach zero. However, in practice, the loss in the ring and coupler cannot be neglected, as it might make the switch unworkable. Therefore, we suggest inserting a gain-controllable optical amplifier into the ring to compensate for the losses and enhance the ring finesse to reduce the switching power. By adjusting the gain, a tradeoff between the switching power and the switching time can be obtained.