Optical channel monitoring technique using phase-modulated pilot tones

We report on the pilot-tone-based optical channel monitoring technique for use in wavelength-division-multiplexing (WDM) networks. The proposed technique can monitor the wavelengths of WDM signals using phase-modulated pilot tones. Unlike the previously proposed monitoring technique using amplitude-modulated pilot tones, the proposed technique does not suffer from the cross-gain modulation and stimulated Raman scattering. The results show that the proposed technique could not be deteriorated by the chromatic dispersion.