Improved sensing performance of D-fiber/planar waveguide couplers

Wavelength selective coupling is demonstrated between the core of a D-shaped optical fiber and a multimode planar waveguide. The fabrication process consists of wet chemical etching of the D-fiber and spin coating or molding to produce the planar waveguide. This fabrication process is shown to produce weak coupling and long interaction length, which exhibits transmission dips with narrow wavelength linewidths. A comb filter is demonstrated with peak separations of 12nm, transmission dips of -20dB, and linewidths of 0.25nm. High sensitivity is demonstrated by showing shift in the transmission dips of -3.16 nm/degree C.