Improvement of four wave mixing efficiency in DSF by clock pumping

In this paper, we investigate utilizing clock modulated signal as a pump to improve the efficiency of FWM in 26.5km dispersion shifted fiber. The experimental results show that, with the clock pumping, the conjugated FWM component has higher intensity than that with the CW pumping. The reason behind it is that SBS process is greatly quenched with the clock pumping, so most power of the pumping light contributes to nonlinear interaction with the probe signal during the propagation through DSF. But for CW pumping greater than Brillouin threshold, most power is depleted by SBS process and converted to backward Stokes light, so less power is left for other nonlinear process such as SPM, XPM and FWM to take place. As a result, the FWM components have lower intensity, and the pump and probe signal spectrum is also much less broadened. The measurement shows that, the improvement of FWM efficiency is negligible when the pump power is less than 10dBm. But when the pump power is greater than about 11dBm, the improvement becomes significant and increases with the increased pump power. When pump power reaches 17dBm, the improvement is increased to about 9dB.