Transverse offset loss between two identical noncircular single-mode waveguides

Abstract

We derive an approximation for the transverse offset loss based on the Laplacian mode-field half-width (MFHW) and far-field second moment for two arbitrary identical noncircular single-mode waveguides. The relation is reduced to the known result for circular-symmetric, single-mode waveguides. Numerical results for symmetrical rectangular waveguides show that the transverse offset loss calculated from the Laplacian MFHW is more accurate than that from the elliptical Gaussian MFHW for small transverse offsets. To our knowledge, this is the first calculation of the errors in the approximate transverse offset loss relations derived from the Laplacian and the elliptical Gaussian MFHW for noncircular optical waveguides.