Chromatic Dispersion Estimation for Optical PDM-QPSK Communication System without Symbol Rate Limitation

Chromatic dispersion (CD) is one of main channel impairments in the ultra-long optical fiber communication based on polarization-division-multiplexing (PDM) technic. Therefore, CD estimation is an important step during coherent detection in the optical receiver. In this paper, an accurate and fast CD estimation method using two mathematical autocorrelation features of received signal is presented. We firstly use the autocorrelation of signal power waveform (ACSPW) to roughly estimate CD value and scanning range, and then singular value of signal autocorrelation matrix (SVSACM) is utilized to search the maximum value in the estimated CD range for accurate CD estimation. Compared with simply used ACSPW in the PDM-quadrature phase shift keying (QPSK) transmission system, the results of numerical simulations show that the proposed method can effectively expand the symbol rates limitation. Moreover, the scanning efficiency of SVACM can be improved to be faster than that without coarse estimation, due to the fact that the CD scanning size becomes relatively small