Intrafiber visible pulse compression by cross-phase modulation in a birefringent optical fiber

Detailed subpicosecond observations of the time dependence of a propagating cross-phase-modulated pulse are presented. It is observed that propagation of a weak visible pulse in one polarization mode of a birefringent optical fiber, so that it is cross-phase modulated by the edge of a strong pulse in the other mode, can result in significant compression of the weak pulse, for normal dispersion, without external compensation. The compression efficiency is found to be enhanced by utilizing the group-velocity mismatch between the two modes to synchronize the weak pulse with the broadening edge of the strong pulse. This is the first observation, to the author's knowledge, of intrafiber pulse compression for normal group-velocity dispersion, and a compressed pulse width of 0.3 psec for a 2-psec input pulse is observed.