Abstract
We investigate and experimentally demonstrate a fast and robust chromatic dispersion (CD) estimation method based on temporal auto-correlation after digital spectrum superposition. The estimation process is fast, because neither tentative CD scanning based on CD compensation nor specific cost function calculations are used. Meanwhile, the proposed CD estimation method is robust against polarization mode dispersion (PMD), amplified spontaneous emission (ASE) noise and fiber nonlinearity. Furthermore, the proposed CD estimation method can be used for various modulation formats and digital pulse shaping technique. Only 4096 samples are necessary for CD estimation of single carrier either 112 Gbps DP-QPSK or 224 Gbps DP-16QAM signal with various pulse shapes. 8192 samples are sufficient for the root-raised-cosine pulse with roll-off factor of 0.1. As low as 50 ps/nm standard deviation together with a worst estimation error of about 160 ps/nm is experimentally obtained for 7×112 Gbps DP-QPSK WDM signal after the transmission through 480 km to 9120 km single mode fiber (SMF) loop using different launch powers.
Highlights
The digital coherent receiver is central in current optical transmission system due to its capability of compensating various transmission impairments
We investigate and experimentally demonstrate a fast and robust chromatic dispersion (CD) estimation method based on temporal autocorrelation after digital spectrum superposition
The fiber optical transmission experiment of 7 × 112 Gbps non-return to zero (NRZ) DP-QPSK WDM signal over 50 GHz grid is conducted to investigate the performance of the proposed CD estimation method
Summary
The digital coherent receiver is central in current optical transmission system due to its capability of compensating various transmission impairments. While no tentative CD scanning is required for the ACSPW CD estimator, 16384 samples can be used for the estimation of accumulated CD at a range of 0~105 ps/nm [11]. Similar to the ACSPW method, the proposed CD estimation requires no training sequences and can operate without tentative CD scanning. The performance of our proposed CD estimation for different modulation formats with various pulse shapes is discussed under ASE noise and PMD with a mean DGD of 25 ps. Through optimizing the digital filters used for the CD estimation, the proposed CD estimation method can operate well for both return to zero (RZ) pulses with different duty cycles and Nyquist pulses with root raised-cosine pulse shaping. We verify the robustness of our proposed CD estimation method against fiber nonlinearity and ASE noise through a 7 × 112 Gbps DP-QPSK WDM transmission experiment. After 480 km to 9120 km SMF loop transmission, the standard deviation of the CD estimation error is around 50 ps/nm, even when the 7 × 112 Gbps DPQPSK signals operate in the nonlinear region
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