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 pri mped with cross-polarized high frequency, saw-tooth pulses from a single pr imp source. Successful polarization-independent wavelength conversion is ex perimentally confirmed with less than +/- 12% and +/-5.6% variation using a gain-switched LD pumping and a mode-locked fiber laser pumping, respective ly. We clarify that the interference effect between two orthogonal pump pul ses must be taken into account to achieve a good polarization-insensitive o peration. since even the small pulse edges bring about the large polarizati on fluctuations when they are interfered. Furthermore. it is reveal that th e shorter pump pulse broadens its own spectrum due to the self-phase modula tion in fibers, resulting in poor FWM efficiency. Finally. possibility of h igh-speed operation is discussed taking into account the pump pulse conditi ons.