BENDING LOSS EVALUATION OF SINGLE-MODE FIBERS WITH ARBITRARY CORE INDEX PROFILE BY FAR-FIELD PATTERN

Bending loss of single-mode fibers has been evaluated based on the measured mode field. Not only the field decay constant but also the normalized field intensity in the cladding has been determined. Experimental results verified the validity of this method. The accuracy of this method is basically determined by the accuracy of field measurement. The mode field is calculated from the far-field distribution measured with a dynamic range of more than 50 dB. Far-field measurement with finite dynamic range limits the accuracy of field evaluation. Dispersion shifted fibers are easier for evaluation because of the wider far-field distribution. Bending loss and mode field diameter can be measured simultaneously with this method, and this method is applicable to any single-mode fibers with a matched clad structure. A microbending loss formula is also determined by the decay constant and the normalized field intensity in the cladding as well as uniform bending loss. © 1990 IEEE