Optoacoustic method for measuring optical losses in fiber-optic waveguides

An optoacoustic method is considered for measuring the radiation absorption and scattering losses in fiber-optic waveguides. It is shown that it is experimentally possible to investigate the distribution of the absorption over the cross section of a fiber-optic waveguide. The results are presented of investigations of fiber-optic waveguides made of Ge₅As₃₄Se₆₁ chalcogenide glass, without an optically reflecting cladding, using CO and CO₂ lasers. It was found that when a sufficiently uniform radiation density distribution over its cross section was excited in a fiber-optic waveguide, the level of the losses in the 5.5-μm region was strongly dependent on the storage period of the waveguide and more than 50% of the losses were due to absorption at the outer surface. The experimentally achieved sensitivity for determining the absorption was β_V = (1–2) X 10^–8 cm^–1 for a radiation power of 1 W and a fiber-optic waveguide length of a few centimeters.