Soliton pulse transmission over long waveguide fiber lengths

An optical circuit for filtering and frequency modulation of solitons propagating in the circuit comprising:

• a non-linear-optical-loop mirror having ends and a length;
• a first coupler having at least two input ports and two output ports, wherein the ends of the optical loop mirror are each optically joined to a respective output port of the first coupler;
• a tap coupler having at least one input port and an output port optically coupled to a point along the optical loop mirror length;
• a splitting coupler having at least one input port and two output ports, a first splitting coupler output port optically joined to a first input port of the first coupler by a first optical fiber and a second splitting coupler output port joined to the input of the tap coupler by a second optical fiber;
• wherein, the respective lengths of the first and second optical fibers are chosen to provide a pre-selected difference in travel time of solitons in the circuit between the respective splitter coupler output ports and said point along the optical loop mirror at which the tap coupler is optically coupled to the optical loop mirror;
• and,
• wherein the difference in travel time is small enough to provide for overlap in the optical loop mirror of the solitons coupled into the optical loop mirror from the output port of the tap coupler and the solitons, which co-propagate with the solitons coupled by the tap coupler, coupled into the optical loop mirror from the first input port of the first coupler.