For the next generation of dynamic optical networks

the fiber length of the transmission link may change dynamically according to the requirement of the optical networks and the chromatic dispersion coefficient may also change due to the aging of optical fiber

which result in the difficulty in the prediction of the cumulative chromatic dispersion value in the transmission link at the receiver side. Thus

it is required that the receiver in the future optical network node can adaptively estimate the cumulative chromatic dispersion for the future compensation process. In this paper

a chromatic dispersion estimation scheme based on the peak to average power ratio is proposed in the digital coherent receiver of optical network nodes. The proposed scheme has been demonstrated in a series of long-haul transmission links of 224 Gbit/s Polarization Division Multiplexing（PDM）-16 Quadrature Amplitude Modulation（QAM） and 336 Gbit/s PDM-64 QAM systems with 400、800、1 200、1 600 and 2 000 km Standard Single Mode Fiber（SSMF）. The results show that the proposed scheme can achieve good dispersion estimation accuracy（the standard deviation is less than 100 ps/nm）. Meanwhile

the proposed scheme has good tolerance for Polarization Mode Dispersion（PMD） and Polarization Dependent Loss（PDL）（when the Differential Group Delay（DGD） is less than 15 ps and the PDL is less than 7 dB

the proposed scheme can achieve good estimation accuracy.）. In addition

the proposed scheme can achieve chromatic dispersion estimation by using only one component of a polarization signal

which greatly saves the computational resources. In addition

the proposed scheme also has good tolerance for the fiber nonlinearity effect.