Evaluation of fiber optical waveguides using brillouin spectroscopy.

Optical scattering loss in fiber optical waveguides is the sum of the bulk material scattering and excess scattering loss due to imperfections in the waveguide structure. The recently developed Brillouin spectroscopic technique for evaluating bulk scattering has been extended to fiber waveguides, and a detailed investigation has been performed on a borosilicate clad-pure fused silica core waveguide. The technique has been found to be useful in evaluating scattering due to waveguide imperfections that have been determined to occur at the core-cladding interface. In addition to providing a measure of the waveguide scattering loss, the Brillouin technique has also been found to be useful in determining the molar composition of the borosilicate cladding glass and the partition of guided optical power between the core and cladding regions. The unusual capabilities of this technique should make it generally useful for characterizing integrated optical structures.