Abstract

Distributed feedback fiber lasers (DFB-FL) based on fiber Bragg gratings (FBGs) written in Er³⁺ or Er³⁺/Yb³⁺-doped fibers are promising candidates for optical communication and sensor applications because of their single longitudinal mode output, narrow linewidth, and ease of fabrication with highly accurate lasing wavelength obtained by current phase mask writing method. Most fiber lasers output consists of two orthogonal linear polarizations if they were fabricated with low birefringent fibers. In contrast, single polarization operation is desirable for optical communication applications. Several techniques have been developed to make fiber lasers operate in single polarization. They included twisting the fiber lasers,¹ introducing a birefringence phase-shift in the fiber lasers,² and self-injection locking^3,4 that employs a polarization dependent/independent feedback to the cavity. In this paper, we investigated the use of active injection locking technique. By injecting the output of a DFB-FL to a Fabry-Perot laser diode (FP-LD), we showed that stable and highly polarized output can be achieved. A power penalty improvement of 3.8 dB was also demonstrated in a 41-km 10 Gb/s transmission test.

© 2002 Optical Society of America