Chromatic Dispersion Monitoring Technique Using Pilot Tone Carried by Broadband Light Source

We propose and demonstrate a simple chromatic dispersion monitoring technique based on the pilot tone generated by a broadband light source (BLS). Previously, the pilot tone has been obtained by directly modulating each transmitter laser with a small sinusoidal current. Thus, for use in the wavelength-division- multiplexed (WDM) network, each transmitter should be modulated with a unique pilot tone. However, we obtain the pilot tone by modulating an additional BLS such as a reflective semiconductor optical amplifier. Thus, there is no need to modulate each transmitter laser. We evaluate the performance of the proposed technique in an 8 times10 Gb/s WDM system. The result shows that, unlike the conventional pilot-tone-based monitoring technique, the performance of this technique is almost insensitive to the polarization-mode dispersion.