Abstract: An improved method is provided for reducing four-wave mixing induced degradation in an optical data signal traversing an optical transport network that uses Raman amplifiers. The method includes: introducing at least two Raman amplifiers into the optical transport network, each Raman amplifier having a laser source, and synchronously modulating the laser sources of the Raman amplifiers, thereby reducing four-wave mixing in the optical data signal. Modulation of the laser sources is performed at such a rate that crosstalk from the modulation to the optical data signals experiencing the Raman gain is minimized.