Enhanced slow and fast light in strong dispersion region of the Raman assisted narrow band fiber optical parametric amplifier

Abstract

Narrow band fiber optical parametric amplifier with normal second order dispersion is deemed as a potential approach to delay the wide band signal in future optical telecommunication. Due to the combined effect of Raman and four-wave mixing, the slow and fast light is complex in this case. By considering both the real and imaginary part of the Raman susceptibility, two formulas for the phase shift and delay time in the stimulated Raman scattering assisted fiber optical parametric amplifier are presented. The wavelengths with maximum delay and advanced time are calculated numerically. Then we find some narrow frequency regions with the enhanced slow and fast light in both stokes and anti-stokes wave regions, which is the result of strong dispersion generated by the interaction between the stimulated Raman scattering and four-wave-fixing effect at the strong absorption region. In a narrow frequency region around the wavelength with maximum delay or advanced time, the case with low pump power and longer fiber can generate large delay(advanced) time if the signal wave has low bandwidth. Meanwhile, the delay or advanced times in these regions are sensitive to the signal wavelength due to the drastic change of the delay time spectrum. Simulation shows that the delay or advanced time will drop with the signal bandwidth. The time difference between two 1 GHz signal waves with 0.02 nm wavelength separation can reach 290ps in the Raman enhanced slow light region when we employ 2.4W pump power and 1km NZ-DSF. These features of enhanced slow and fast light in the interaction between the stimulated Raman scattering and four wave mixing effect has the potential to be applied in the optical signal processing.