OSCILLATING NONLINEAR FREQUENCY CHIRP IN A SINGLE-MODE OPTICAL-FIBER

The frequency chirps of the pump pulses propagated through a 1.85 km l ong single mode optical fiber has been measured by a spectrograph foll owed by a streak camera with various input energies at a constant puls e width. The spectrotemporal distribution of oscillating nonlinear fre quency chirp has been observed when the input energy is increased to 3 0 nJ with an input pulse width of 90 ps. The simulation showed that th e oscillation is caused by initial amplitude modulation on input pulse s combined with stimulated Raman scattering (SRS) during the pulse pro pagation along the optical fiber.