Enhancing the monitoring range and sensitivity in CSRZ chromatic dispersion monitors using a dispersion-biased RF clock tone

We demonstrate a technique for 10- and 40-Gb/s chromatic dispersion monitoring for carrier-suppressed return-to-zero (CSRZ) signals using the radio-frequency (RF) power at the bit rate frequency (the "clock" frequency) that significantly enhances the monitoring range and sensitivity. We show that conventional RF clock tone monitoring techniques result in a small monitoring range and sensitivity when applied to CSRZ signals. We use fixed positive and negative dispersion elements to "bias" the RF clock power and extend the monitoring range for 10- (40-) Gb/s signals from 480 (30) to ∼752(48) ps/nm. In addition, the sensitivity is enhanced from 0.0048 (0.0476 dB/ps/nm) to 0.0106 dB/ps/nm (0.1667 dB/ps/nm). Applying this monitoring technique to a dynamic chromatic dispersion compensation system, we compensate for the dispersion of 20-40 km of single-mode fiber (SMF) [step size of 5 km] and show <0.2-dB power penalty (compared to the back-to-back receiver sensitivity at 10^-9 bit-error rate) by maximizing the biased RF clock component for the worst scenario after compensation (40 km of SMF).