New fiber laser design for application in phase sensitive optical time domain reflectometry

Abstract

We have employed a new injection locking DFB laser configuration for detection and localization of the perturbations in phase sensitive OTDR system. The spectral performance of available DFB laser source has been significantly improved with implementation of self-injection locking mechanism. To provide the effect, a part of the optical radiation emitted by the laser is returned back into the laser cavity through an external fiber optic ring resonator. Self-injection locking of DFB laser coupled with the ring cavity in the under-coupled, critically coupled, and over-coupled regimes has been tested bringing us to the conclusion that the best locked laser stability and narrower linewidth is observed with the critical coupling. With the laser operating in this regime an accurate localization of 50 Hz harmonic perturbation with the spatial resolution of ~10 m at the distance of 9270 m is experimentally demonstrated with phase sensitive OTDR technique.