Bending losses in single-mode fiber waveguides

An experimental investigation was made of the bending losses in single-mode step-index fiber waveguides with different parameters of the equivalent step profile for bending radii from 7.5 to 40 mm. In the case of fibers with a shock-absorbing cladding, wound on small-radius drums without tension, the results could be described by calculation formulas derived in the approximation of radiative bending losses. It was found that in the case of waveguides wound on drums of ~10 mm radius the bending losses can be reduced by selecting fibers with Δn~0.01 and by operating at a normalized frequency V close to 2.4. Winding of fibers under tension gave rise to additional losses which depended on the structure of the cladding. These losses were attributed to the appearance of local bends of smaller radius.