Three-layer optical waveguides of the ring type

An experimental investigation was made of the attenuation in the 0.8–1.6 μ wavelength range, and of the pulse broadening at wavelengths 0.87 and 1.3 μ, in three-layer ring-type optical fiber waveguides. In a waveguide having a large difference between the refractive indices, filtering out the higher-order modes resulted in no great increase in the attenuation. For a waveguide with an intermediate cladding whose thickness was considerably less than its radius, no pulse broadening was recorded at 1.3 μ wavelength.