STRAIN DISTRIBUTION MEASUREMENT IN BENT OPTICAL CABLES USING A FIBER RIBBON WITH MULTI-POINTED FIBER BRAGG GRATINGS

摘要

Strain distribution along an optical fiber inside a cable were optically measured by placing Fiber Bragg Gratings (FBG) of different reflecting wavelengths on the fiber. As a method for controlling the reflecting wavelength of each grating, different tension was applied to the fiber during UV exposure. We controlled the Bragg wavelength for 17nm (approx. 1.4% tension) with a single mask. Gratings were fabricated at regular intervals on a fiber for a slot type optical-fiber cable. The strain distribution induced by bending the cable was observed. Distribution measurements in a spatial resolution of 50mm, strain measurement accuracy of 0.002% was possible. We confirmed a strain distribution responding in accordance to the structure of the slot type cable. The fiber has the mechanical strength of normal fibers as the FBGs are made by UV exposed over the coating. The fibers can be used in the cabling process and also in traction and laying.