Twisted hi-bi fiber distributed-feedback lasers with controllable output state of polarization

We demonstrate that single polarization, hi-bi fiber DFB lasers are, in general, characterized by elliptical state of polarization (SOP), due to the in-built fiber birefringence axis rotation. Externally applied birefringence axis twist is shown to provide accurate control of the output SOP. Continuous tuning from circular to linear polarization, with polarization extinction ratio of ~40 dB, has been demonstrated