Influence of Acoustic Perturbation of Fibers in Phase-Noise-Compensated Optical-Frequency-Domain Reflectometry

We show that the performance of phase-noise-compensated optical-frequency-domain reflectometry (PNC-OFDR) is affected by the acoustic phase noise caused by environmental acoustic perturbations applied to test fibers. When both the auxiliary interferometer and the fiber under test are insulated against acoustic perturbation, the theoretical spatial resolution is obtained. This means that a laser-induced phase noise compensation scheme with a concatenative reference method (CRM) works almost ideally and eliminates the phase noise even over a 40-km range, with 16-fold concatenation. We also reveal that even when we use a laser with a very narrow linewidth of a few kHz, the phase noise of the laser remains a dominant factor in performance degradation, and the CRM works effectively over the range. Test results for an actual fiber cable installed in underground show that there was no severe degradation in performance, and that PNC-OFDR sustained its unique high resolution in actual field use.