Experimental and theoretical investigation of a polished-type single-mode fibers coupler with an intermediate planar waveguide

Experimental and theoretical results concerning the characteristics of polished single-mode fiber-optic couplers with an intermediate waveguiding optical layer between the two fiber half- blocks are presented. Different theoretical approaches are compared and a suitable equivalent planar geometry is chosen and treated in the limits of coupled-mode theory. Mechanism of light transfer from first to the second coupler channel is investigated. Both the experimental and theoretical results are presented concerning the properties of the glued optical fiber coupler for three different thicknesses of the glue layer. These couplers are compared in respect to their spectral characteristics.