Phase-Regenerative DPSK Wavelength Conversion

Phase-sensitive amplifiers (PSAs) effectively reduce accumulated phase noise (PN) in differential-phase-shift keyed (DPSK) communications systems. Their inherent complexity is offset by the ability to mitigate several impairments simultaneously: PSAs can regenerate phase and amplitude at the same time, while amplifying, reshaping and re-timing pulses. This work explores the addition of another important networking function, wavelength conversion (WC), to an established PSA architecture, to provide phase-regenerative wavelength conversion (PR-WC). PSA occurs through four-wave mixing (FWM) processes in fiber. Although it was not specifically studied, the two-stage process (Bragg scattering: BS, followed by phase-conjugation: PC) in provides PSA of an idler at a new wavelength. The two-stage scheme is inhibited by the requirement to phase-lock one distant-frequency pump wave to the other pumps and the signal, and the need to optimize power exchanged in each stage. This work investigates, through theory and experiments, a single-stage PR-WC scheme that eliminates these drawbacks. PR-WC has also been studied using semiconductor optical amplifier-based devices, which require cascaded operation to significantly reduce PN.