Investigation of optical losses in glass-fiber waveguides

A study was made of the optical losses in several batches of glass-fiber waveguides. These waveguides had a core of pure quartz glass and borosilicate cladding; the refractive index profile had a step of Δn≈0.01. The spectra of the total losses α(λ), radiation losses ρ(λ), and absorption losses κ(λ) were investigated in the wavelength range 0.45–1.1 μ. The effects of technological factors were investigated by determining the absorption losses in the blanks and the distribution of radiation losses along the finished waveguides. It was found that most of the waveguides were characterized by the following losses in the maximum transparency (λ=0.7–0.85 μ) range: α≈7–10 dB/km, ρ≈6–8.5 dB/km, κ≈1.0–1.5 dB/km. These results were evidence of a high degree of purity and homogeneity of the core material and they demonstrated that the process of drawing of the fibers did not give rise to any significant absorption losses and that the total losses in the λ=0.7–0.85 μ range were dominated by the escape of radiation because of geometric imperfections.