Implementation of a widely tunable microwave signal generator based on dual-polarization fiber grating laser

摘要

In this paper, we demonstrate the implementation of a widely tunable microwave signal generator based on a dual-polarization fiber grating laser. The laser contains two strong, wavelength-matched Bragg gratings photoinscribed in an Er-doped fiber and emits two polarization modes when pumped with a 980 nm laser diode. By beating the two modes, a microwave signal with a signal-to-noise ratio over 60 dB can be obtained. For a free running laser the fluctuations in intensity and frequency of the microwave signal are +/- 1 dB and +/- 5 kHz, respectively, and the noise level is about -40 dBc/Hz at 1 kHz. The frequency can be continuously tuned from 1.8 to 15.1 GHz, by transversely loading the laser cavity and changing the intracavity birefringence by use of a piezoelectric transducer-based mechanical device. The measured response time rate of tuning is about 90 MHz/mu s and the intensity fluctuation at different frequencies is less than +/- 1.5 dB. The frequency fluctuation under loading is controlled within 1 MHz by introducing an electrical feedback.

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