{HEAD ~ An optical waveguide structure} has a single port on one input/output side, a plurality of ports on another input/output side and an S curve optical waveguide portion arranged on the outermost side of the waveguide structure and including {TAIL ~ a first circular arc optical waveguide portion} and a second circular arc optical waveguide portion connected thereto 
{ HEAD ~ An optical waveguide structure } has a single port on one input / output side , a plurality of ports on another input / output side and an S curve optical waveguide portion arranged on the outermost side of the waveguide structure and including { TAIL ~ a first circular arc optical waveguide portion } and a second circular arc optical waveguide portion connected thereto
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