Karl-Friedrich Klein

Infrared absorption of silica fibers

Based on precise measurements of the attenuation coefficient an extended formula was developed for the calculation of the infrared absorption of silica between 1.3 μm and 1.7 μm wavelength, using a silica-based single-mode fiber with undoped core and fluorine-doped cladding. Below 1.3 μm, the infrared absorption is negligible due to our analysis: < 0.001 dB/km. Above 1.3 μm, the infrared absorption increases slowly with increasing wavelength; however, the slope becomes much steeper around 1.5 μm. Therefore, this function can be approximated more precisely by two exponential functions instead of only one exponential function as assumed so far. The four coefficients have been determined. At 1.55 pm, we obtained an infrared absorption coefficient of α IR,λ = 0.014 dB/km, which is in the middle of the values (0.021 dB/km respectively 0.009 dB/km) determined in the past.

Infrared Radiation Loss Measurements of a Quartz Capillary

A carbon dioxide laser was used to measure the transmission of a 0.5 mm diameter hollow quartz fiber near the first lattice absorption band, where the refractive index is below unity. The experimental values are close to the theoretical expectations. The laser measurements were supplemented by measurements with a continuously tunable incoherent light source.