Polished fiber-optic coupler with intermediate planar waveguiding layer. II

For pt.I see ibid., vol.10, p.882-7 (1992). A theoretical approach for calculating the optical characteristics of single-mode fiber-optic couplers with an intermediate planar waveguiding layer in an equivalent planar geometry by coupled mode theory and an approximation of a fiber curvature by subdividing the structure into a great number of parallel sections is suggested. In this way the mechanism of light transfer from first to second coupler channel is investigated. It is shown that for some parameters of the coupler a part of optical power remains in the intermediate layer, i.e. losses arise in the coupler.>