A fibre ring resonator using a 3×3 optical fibre coupler

Various fibre components have been explored in recent years for use as wavelength division multiplexers and demultiplexers. The inherent wavelength selectivity of 2×2 fused couplers has been exploited but relatively long interaction lengths are required to achieve narrow channel separation. Combining a fibre coupler with a ring resonator results in a very narrow band filter but has the restriction that only one input port and one output port is available. The authors present a novel device based on forming a ring resonator from a 3×3 fused coupler, which has the advantage of two input ports and two output ports and can be used for wavelength division multiplexing/demultiplexing and for switching of optical signals