Wavelength-swept sources have been playing an important role in biomedical imaging and sensing applications. A desirable wavelength-swept source has features such as a wide wavelength range, fast sweep rate, high linearity and narrow linewidth in order to capture maximal interferometric information or enhance the spatial resolution. Previous efforts on wavelength-swept sources have been demonstrated in erbium-doped fiber lasers, semiconductor lasers and optical parametric oscillators. However, most of the time these techniques can only operate at certain wavelength ranges or the setup was complicated and required a dedicated alignment of optimal operation. On the other hand, FOPOs eliminate the need for alignment and allow swept signal generation in potential regions where practical gain medium may not be available yet. Using the FOPO configuration, a wavelength swept source has been demonstrated with a 329-nm tuning range, but the cumulative speed is limited to 70,000 nm/s. So it is highly desirable to increase the speed of such kind of swept source.

We demonstrate a fully fiber-integrated FOPO with a wavelength range of 109 nm, sweep rate of 40 kHz pumped by a simple clock-modulated pump. Tuning is achieved by changing the clock frequency linearly from 1 GHz to 1.0006 GHz. A 150-m highly-nonlinear dispersion-shifted fiber (HNL-DSF) is deployed inside a cavity as the parametric gain medium. Pulses with pulsewidth of 150 ps are generated. This scheme has the potential to be a cost-effective source in generating swept signal for biomedical imaging outside the conventional wavelength window.