Chromatic Dispersion Monitoring by Synchronizing the Two Sidebands of the Received Optical Signal

Abstract

In this paper, a new chromatic dispersion (CD) monitoring technique is proposed in optical fiber networks. It is based on detecting the relative group delay between the upper and lower sidebands of the monitored signal (induced by CD) by shifting the two sideband signals a number of times and at every time they are converted to the same frequency, and then they are coupled together with a phase difference of (180o) and the resulting signal power is measured. In one of the shift stages, it obtains minimum power when the time shift equals the relative group delay (i.e. the two sideband signals are synchronized). Therefore, the relative group delay can be detected through searching the minimum output power and the corresponding time shift. The proposed technique is characterized, compared with other monitoring techniques, by good monitoring range with the ability to determine chromatic dispersion sign, high measurement resolution, fixed sensitivity over the whole measurement range, no modification of the transmitter, not affected by polarization mode dispersion (PMD), good tolerance to the amplified spontaneous emission (ASE) noise and the potential to monitor several channels in wavelength division multiplexing (WDM) networks.