Research of behavior of optical fibers in fiber optic cable loose tubes under deformation

Fiber optic cables with multiunit core composed of loose tubes with optical fibers are widely used over networks installed in Russia. There are different mechanical loads including crushing load that influence on fiber optic cables during their installation. Early on papers considered only single fiber loss increasing due to cable deformation produced by crushing load. However, conventional fiber optic cables usually contain from 4 to 12 optical fibers in the each loose tube. Therefore, this work is concerned on research of fiber bundle behavior under loose tube deformation. A supposition was made and then proved, that during loose tube deformation a sharp increase of fiber loss is caused by fiber-to-fiber bends instead microbends due to loose tube surface undulation. Those radiuses of fiber-to-fiber bends are determined. Sharp increase of fiber loss (more than 0.05 dB) occurs under fiber-to-fiber bend radius as less than 8 mm.