Orientation- and polarisation-dependent cutoff wavelengths in elliptical-core single-mode fibres

The direct measurement of cutoff wavelengths from the spectral dependence of the near-field intensity distribution has been improved by selectively exciting the first higher-order mode and applying it to elliptical-core single-mode fibres. Depending on the orientation and polarisation of the first higher-order mode, four different cutoff wavelengths have been identified.