Abstract:

In this study, a method for maintaining polarization- output of a distributed feedback fiber laser (DFB-FL) via polarization coupling method is proposed. DFB-FL is a type of narrow-line-width light source produced via phase shift grating etched on an active optical fiber. The grating formation process based on side exposure will induce the tangential index distribution polarization of the fiber, ensuring that the narrow-line-width laser exhibits single linear polarization characteristics. The output fiber of DFB-FL can be replaced with a polarization-maintaining fiber using the polarization-maintaining welding machine. During this process, the angle between the laser polarization direction and the slow axis of the polarization-maintaining fiber of DFB-FL can be adjusted by rotating the fiber. Moreover, the change in the laser power and polarization extinction ratio can be measured using a power meter and extinction ratio tester. When both the laser power and polarization extinction ratio are maximum, polarization coupling can be achieved between DFB-FL and the polarization-maintaining fiber. Results show that the polarization extinction ratio of the DFB-FL is greater than 30 dB and the polarization state is linearly polarized. Compared with the single-mode output fiber laser, the laser efficiency, line width, and noise of the polarization-maintaining output fiber laser show no significant changes.

Key words: fiber laser, distributed feedback fiber laser, polarization mode coupling, polarization-maintaining fiber laser, narrow linewidth