Radiation losses in glass fiber waveguides due to variations of the waveguide cross section

A study was made of the variation of the outer diameter D(z) and of the radiation lose distribution r(z) along the length of a glass fiber waveguide with a graded refractive index profile and a nominal outer diameter of 125 μ. Each minimum of D(z) corresponded to a peak of r(z). Variation of D within a range of 5% gave rise to radiation losses of about 2 dB/km in the spectral range 0.48–0.68 μ.