Transmitter IQ skew severely degrades the performance of coherent optical communication systems, especially for high baud-rate and higher order quadrature amplitude modulation (QAM) systems. Utilizing Nyquist pulse shaping can increase the spectral efficiency of WDM systems, while sharp roll-off of Nyquist pulse shaping further reduces the tolerance to residual IQ skew. Thus, there is a tradeoff between WDM system spectral efficiency and its tolerance to residual IQ skew. In this talk, we review the impact of Nyquist pulse shaping on the tolerance to residual IQ skew. The roll-off factor, channel spacing, receiver bandwidth and equalizer length are optimized given certain residual IQ skew. We further discussed the potential application scenarios and the methodologies to apply this technique. The results serve as guideline for high baud-rate coherent long-haul optical communication systems.

Date Published: 14 February 2019
PDF: 5 pages
Proc. SPIE 11048, 17th International Conference on Optical Communications and Networks (ICOCN2018), 1104819 (14 February 2019); doi: 10.1117/12.2520481

Published in SPIE Proceedings Vol. 11048:
17th International Conference on Optical Communications and Networks (ICOCN2018)
Zhaohui Li, Editor(s)