Polarization-independent wavelength conversion using four-wave mixing in single-mode fibers pumped with cross-polarized high frequency pulses

This paper describes a simple polarization-independent wavelength conversio n method using degenerated four-wave mixing (FWM) in single-mode fibers pum ped with cross-polarized high frequency, saw-tooth pulses from a single pum p source. Successful polarization-independent wavelength conversion is expe rimentally confirmed with less than +/-12% and +/-5.6% variation using a ga in-switched LD pumping and a mode-locked fiber laser pumping, respectively. We clarify that the interference effect between two orthogonal pump pulses must be taken into account to achieve a good polarization-insensitive oper ation, since even the small pulse edges bring about the large polarization fluctuations when they are interfered. Furthermore, it is reveal that the s horter pump pulse broadens its own spectrum due to the self-phase modulatio n in fibers, resulting in poor FWM efficiency. Finally, possibility of high -speed operation is discussed taking into account the pump pulse conditions .