Group velocity manipulation in active fibers using mutually modulated cross-gain modulation: From ultraslow to superluminal propagation

We propose and experimentally demonstrate the propagation of slow/fast light in an erbium-doped fiber (EDF) using mutually modulated cross-gain modulation. The group velocity of the light signal can be manipulated by the effect of gain cross-saturation modulation by a saturating light at an arbitrary wavelength in the gain bandwidth of the EDF. The ultraslow propagation with a small group velocity of 5:6 × 10^-3+ (c is the light speed in free space) and superluminal propagation with a negative group velocity of -1:1 × 10-3c has been observed under different modulation phases.