Simulation of the near field of single-mode fibres by means of a microwave model

In order to verify the agreement of the conventionally used approximations for the field equations of the fundamental mode of a fibre and to study the near field in the vicinity of a discontinuity, a microwave model of a single-mode fibre is designed and constructed. At this waveguide, which works at frequencies of about 10 GHz, the field distribution can be measured with a small microwave probe. Using a semi-automatic level- and wavefront-recorder the field pattern of the radiating fibre end, as well as that in the vicinity of a gap, a displacement or an angle, is plotted and discussed.