Field Trials of PNC-OFDR in Different Environments for Detecting Short Beat Lengths

A spatial resolution of 10 cm was obtained for distances of 60~80 km in different field environments using phase-noise-compensated optical frequency domain reflectometry. The outstanding spatial resolution makes it possible to identify high-birefringence sections along installed cables. In field trials, we successfully observed beat lengths as small as ~20 cm, which showed that there were very large birefringence sections in the installed cables. To the best of our knowledge, this is the first time that such short beat lengths have been directly detected in a nondestructive measurement for long fibers, and the result will be very useful in relation to fiber management.