Radiation Characteristics of Circular Dielectric Waveguides

The radiation characteristics of isolated circular optical waveguides capable of supporting only low-order dielectric waveguide modes are studied both theoretically and experimentally for several combinations of modes, wavelength, diameter, and waveguide numerical aperture. Photographic and photoelectric measurements of the far-field intensities are compared with numerical predictions based on the equivalent current method of Schelkunoff. For a cross-sectional intensity distribution in the mode pattern of the approximate form $J_{n+1}^2(ur/a)$ the predicted Fraunhofer pattern has the form: