| 1. |
- Karout, Johnny, 1985, et al.
(author)
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CMA Misconvergence in Coherent Optical Communication for Signals Generated from a Single PRBS
- 2011
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In: Wireless & optical communications conference, New Jersey, 15-16 April 2011. - 9781457704543
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Conference paper (peer-reviewed)abstract
- In the experimental study of modulators for coherent optical communications, it is common to generate multilevel signals using a single pseudo-random binary sequence. This simple experimental realization leads to symbol correlation. When modulators are studied in combination with adaptive receiver algorithms that rely on independent data, misconvergence may result. In this contribution, we investigate the impact of such correlation on a standard blind equalization method and provide guidelines to avoid misconvergence. Our results indicate that care needs to be taken when using a single PRBS sequence and that decorrelation delays must be chosen appropriately. We present simulation and theoretical results for 16-QAM, and show how our results can be applied to other multi-level constellations.
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| 2. |
- Tavan, M., et al.
(author)
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The Impact of Polarization-Dependent Loss on the Constant Modulus Algorithm for Varying Number of Fiber Spans Based on an Outage Criterion
- 2011
-
In: Proc. Wireless and Optical Communications Conference (WOCC). - 9781457704543
-
Conference paper (peer-reviewed)abstract
- We investigate the effect of polarization-dependent loss (PDL) on the constant modulus algorithm (CMA) in 4-QAM and 16-QAM polarization multiplexed (PolMux) systems with varying number of fiber spans and different PDL values. To quantify this effect, outage probability is introduced as the probability of having a signal-to-noise ratio (SNR) degradation smaller than 1 dB 99% of the time. We observe that by increasing the number of fiber spans, the SNR penalty for CMA reaches a limiting value. Moreover, in the 16-QAM multi-span case, the effect of PDL on CMA depends on the amount of PDL, while for 4-QAM, the effect of PDL on CMA is insensitive to the amount of PDL. These results will provide guidelines for designing systems and adjusting transmission power.
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