Phase-locked dual-polarization fiber lasers as compact optical-microwave sources

Fully fibered microwave-optical sources at 1.5 µm are studied experimentally. It is shown that the beat note between two orthogonally polarized modes of a distributed-feedback fiber laser can be efficiently stabilized using an optical phase-locked loop, that uses the pump-power induced-birefringence as actuator. Beat notes at 1 GHz and 10 GHz are successfully stabilized to a reference synthesizer, passing from the 3 kHz free-running linewidth to a stabilized sub-Hz linewidth, with a phase noise as low as –75 dBc/Hz at 100 Hz offset from the carrier. An Erbium-Ytterbium co-doped fiber laser is also investigated. Such dual-frequency stabilized lasers could provide compact integrated components for RF and microwave photonics applications.