{HEAD ~ The present invention} concerns {TAIL ~ a multi wavelength selective switch} in the form of a directional coupler structure 
concerns
{ HEAD ~ The present invention } concerns { TAIL ~ a multi wavelength selective switch } in the form of a directional coupler structure
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH