Measurement of radiation loss in curved single-mode fibres

Experimental and theoretical studies on the radiation loss from curved single-mode fibres show that it includes contributions due to transition loss at discontinuities between straight and curved sections of fibre, as well as the bend loss due to uniform curvature. These two contributions have been measured separately, and there is good agreement with the theoretical predictions. The transition loss at large bend radii can be considerably greater than the uniform bend loss. It is found that the transition loss incurred by a change of fibre curvature from R to ¿¿R is about 8 times bigger than that from R to ¿¿. The loss due to fibre undulation has also been measured and in this case the results can be completely explained using only the pure bending loss theory.