{HEAD ~ The waveguides} in one section are arranged in {TAIL ~ the proximity} of each other, such that an optical field in the first waveguide can overlap a second waveguide and vice versa and that in said section at least two gratings are arranged for co directional coupling 
are arranged in
{ HEAD ~ The waveguides } in one section are arranged in { TAIL ~ the proximity } of each other , such that an optical field in the first waveguide can overlap a second waveguide and vice versa and that in said section at least two gratings are arranged for co directional coupling
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH