ACCURATE ELASTO-OPTIC PROBE METHOD FOR MEASUREMENT OF COUPLING LENGTHIN TWIN-CORE OPTICAL-FIBER

The theoretical principle and experimental procedure of a new method o f measuring the coupling length of a twin-core fiber are presented. Th is method is simple, nondestructive, and gives direct results without extensive data processing. It is based on the elasto-optic technique a nd had a very good spatial resolution so that coupling lengths of the order of a few millimeters can be measured. We show how this method ca n be applied to the measurement of the polarization coupling of birefr ingent noncircular twin-core fibers.