Method and system to reduce FWM penalty in NRZ WDM systems

An optical transmission network comprising:

• a long fiber waveguide;
• a plurality of sources of modulated optical signals each having a different wavelength;
• a multiplexer coupled to each of said sources for receiving the modulated optical signals and transmitting the optical signals over said long fiber waveguide;
• and
• a phase modulator for modulating the phase of the optical signals propagating through the long fiber waveguide,
• wherein said phase modulator modulates the optical signals at a frequency that causes destructive interference of four wave mixing cross-talk products generated along the length of the long fiber waveguide.

An optical transmitter for use in an optical transmission network having a long fiber waveguide through which a plurality of wavelength division multiplexed signals are transmitted, said transmitter comprising:

• a plurality of sources of optical signals each having a different wavelength;
• a plurality of phase modulators for separately modulating the phase of the optical signals supplied from the plurality of sources;
• a multiplexer coupled to each of said phase modulators for receiving the phase-modulated optical signals and transmitting the optical signals over said long fiber waveguide;
• and
• an optical amplifier for amplifying the phase-modulated optical signals as the optical signals propagate through the long fiber waveguide,
• wherein said phase modulators modulate the optical signals at a frequency that causes destructive interference of four wave mixing cross-talk products generated along the length of the long fiber waveguide.