Colliding visible picosecond pulses in optical fibers

The observation of the nonlinear interaction of two visible picosecond pulses, separated by a small time interval, while propagating in an optical fiber is reported. It is found that as propagation proceeds, a region of pulse collision develops in which intensity oscillations form that are similar to those recently observed in optical wave breaking. The frequency of these oscillations increases for an increasing time separation between the input pulses and is found to be as large as 5 THz. For small time intervals between the input pulses no oscillations formed. This observed behavior is found to agree well with numerical integrations of the nonlinear Schrödinger equation.