PROCESS AND EQUIPMENT FOR MEASURING THE CUT-OFF WAVELENGTH OF THE FIRST HIGHER ORDER MODE IN OPTICAL FIBRES

摘要

The process is based on the fact that the introduction of perturbations in an optical fibre can generate greater losses on higher order modes. Therefore, a spectral scanning of the fibre output power is effected under a certain number of different perturbation conditions and the values obtained are combined so as to determine the fraction of power guided in the fundamental mode. The cut-off wavelength is that where this fraction exceeds a certain value. The equipment implementing the process is also provided.