Abstract
Electronic predistortion (EPD) to compensate for chromatic
dispersion is an attractive option to replace inline optical dispersion
compensation (ODC). In this paper, we present a study on the impact of
intra- and interchannel nonlinearities in EPD systems compared to optimized
ODC systems at 10 and 40Gbit/s for NRZ-OOK modulation.
First, the theoretically achievable nonlinear tolerance of EPD and ODC
systems is studied by neglecting the EPD transmitter's hardware limitations
and the dispersion compensating fiber's loss and nonlinearity. At
10Gbit/s, EPD shows stronger degradations due to intra-
and interchannel nonlinearities than optimized ODC. We extend existing
studies for 10 Gbit/s EPD by analyzing the relevant launch power levels
before interchannel nonlinearities limit the performance. The limit is 8 dB
larger for ODC than EPD at 10 Gbit/s. In contrast, operating at a bit rate
of 40 Gbit/s significantly reduces this difference in the nonlinearity
tolerance between EPD and ODC both for single channel and WDM transmission.
The maximum power per channel of 40 Gbit/s EPD is only 1 dB smaller compared
to ODC.We then conduct a more realistic comparison at 40 Gbit/s by
including the effects of 60 GSa/s digital-to-analog conversion with 4-bit
quantization in the EPD transmitter and by considering the loss and
nonlinearity of the dispersion compensating fiber. Analyzing the optical
signal-to-noise ratio margins confirms that the performance of the realistic
EPD system is similar to optimized ODC making EPD more attractive for
electronic dispersion compensation at bit rates of 40 Gbit/s and
above.
© 2009 IEEE
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