Correlation-based transceiver in-phase/ quadrature skew in-field calibration in dual-polarization coherent optical transmission system.

Abstract

In this paper, we propose a novel transceiver in-phase/quadrature (I/Q) skew in-field calibration scheme with correlation-based method for the dual-polarization coherent optical system. Simultaneous dual-polarization calibration of transceiver I/Q skews after fiber transmission is experimentally performed. Rx/Tx correlation-based skew estimations (CBSEs) are proposed to accurately estimate the transceiver I/Q skews with dual-polarization OFDM signal. By simulation, the robustness of the Rx/Tx CBSEs is investigated against various transceiver I/Q imbalances and channel impairments including carrier frequency offset (CFO), phase noise (PN), and chromatic dispersion (CD). The simultaneous measurement of large transceiver skews is studied within a range of ±128 ps. The bit error rate (BER) improvement brought by the CBSEs is studied in 80 km single-mode fiber (SMF) transmissions under various Rx/Tx skews. In the experiments, the Rx/Tx skew is measured in the range of 1 to 128 ps w/ and w/o the presence of 5 ps Tx/Rx skew. Simultaneous dual-polarization measurements are performed with the X/Y polarization Tx/Rx skews set to 2.5 ps, 5 ps, 7.5 ps and 10 ps, respectively. The measurement errors are within ±0.2 ps. The 80 km SMF dual-polarization transmission after in-field calibration for inter-data center interconnection (inter-DCI) is implemented, with a data rate of 400 Gb/s for both 16QAM and 32QAM modulation formats.