Impact of Differential Group Delay on 100 $Gb/s\lambda$ IM/DD Passive Optical Networks

The 100 $\text{Gb}/\mathrm{s}/\lambda$ passive optical networks (PONs) based on the intensity-modulation and direct-detection (IM/DD) optical systems are still potential candidates for the next-generation PON. However, in addition to the limited bandwidth and chromatic dispersion, differential group delay (DGD) is a potentially great challenge for the 100 $\text{Gb}/\mathrm{s}/\lambda$ IM/DD PONs. DGD not only causes inter-symbol interference but also seriously affects timing recovery. In this paper, we evaluate the impact of DGD on the 100 $\text{Gb}/\mathrm{s}/\lambda$ IM/DD PON. The results show that the bit-error ratio is seriously degraded. Although more powerful digital signal processing is used, the penalty on the receiver sensitivity still exists. Moreover, the variance of the timing error is larger with the increase of DGD, which would be a great challenge to implement timing recovery for the 100 $\text{Gb}/\mathrm{s}/\lambda \text{IM}/\text{OD}$ PONs.