Integrating sphere for measuring scattering loss in optical fiber waveguides

An integrating sphere for light scattered from fused silica optical fiber waveguides that is relatively simple to construct and easy to use is described. The novel feature is the use of a solid sphere of fused silica to facilitate coupling the scattered light out of the fiber cladding into the detector. The fiber is inserted into a slot in the sphere, and glycerine is used to index match between the fiber and sphere. The sphere is coated with high reflectivity barium sulfate, and a silicon photodiode detects the radiation in the sphere. The construction, operation, and performance tests on the sphere are described.