Far-field radiation and modal dispersion of 1310 nm dispersion-optimized fiber at 850 nm

Far-field radiation pattern measurements have been used to evaluate the modal structure and dispersion associated with 0.85-μm wavelength light launched from high-brightness light-emitting diodes into TIA class-IVa fiber. The measured far-field radiation pattern of the light intensity emitted from the end of the optical fiber is compared to the far-field radiation pattern calculated from the Fraunhofer approximation to the diffraction integral with the result that two linearly polarized modes propagate in the optical fiber and the optical power is nearly equally distributed between the two modes. The modal dispersion associated with the use of a 0.85-μm wavelength emitter and a TIA class-IVa fiber is evaluated to be 2.3 ns/km, which is adequate for a variety of local-area networks and point-to-point optical communication links