Insertion Loss Reduction Between Single-Mode Fibers And Diffused Channel Waveguides.

Methods of reducing the insertion loss between single-mode fibers and graded-index channel waveguides, namely annealing and back-diffusion, are analyzed theoretically and compared. Mode mismatch and misalignment losses are calculated in order to determine the best method and the optimal conditions for its use. The main result of this paper is that, for the single-mode regime, there is no apparent advantage in using back-diffusion instead of the simpler annealing process, in contrast with the multimode case.