Dynamic Control of Phase Matching in Four-Wave Mixing Wavelength Conversion of Amplitude- and Phase- Modulated Signals

We propose and experimentally demonstrate dynamic control of phase-matching in fiber-based four-wave mixing (FWM) for wavelength conversion of communication signals. By introducing self-compensation of optical gain/loss with stimulated Brillouin scattering (SBS) pump and Stokes waves, the FWM phase-matching condition and hence the conversion efficiency (CE) can be flexibly controlled. The phase difference between the interplaying fields is manipulated by modifying the refractive index through SBS without disturbing the initial parameters of the FWM process. The scheme is first applied to wavelength conversion of 10 Gbit/s non-return-to-zero (NRZ) on-off-keying (OOK) signal. Its performance on phase-transparent wavelength conversion is subsequently examined using 10 Gbit/s NRZ differential-phase-shift-keying (DPSK) signal. Eye diagrams, FWM spectra and bit-error rate (BER) performances for the converted signals without SBS, with gain-transparent SBS for maximum CE and for minimum CE are analyzed. In the OOK/DPSK wavelength conversion with gain-transparent SBS, the CE has been reduced by 10.7/11.4 dB at a signal-pump spectral spacing of 1.9/1.94 nm; while it has been enhanced by 8.8/7.4 dB at a signal-pump spectral spacing of 4.1/4.07 nm. The pronounced enhancement of the CE at large signal-pump spectral spacing results in enlargement of the 3-dB FWM conversion bandwidth. Limitations in the extent of bandwidth enlargement and noise performance are discussed. Potential use of the scheme in other applications is also described.