ADAPTIVE NONLINEAR CANCELLATION FOR HIGH-SPEED FIBEROPTIC SYSTEMS

In this paper, we propose techniques for adaptive nonlinear cancellation of intersymbol interference in the electrical signal at the receiver in Gb/s lightwave systems, and describe several demonstrations of these techniques. We first discuss techniques for adjustable nonlinear cancellation, and describe demonstrations of these techniques using commercially available integrated circuits (IC's) at data rates as high as 1.7 Gb/s. We then discuss techniques for automatic adjustment and describe a demonstration of adaptive nonlinear cancellation at 450 Mb/s. Our experimental results show that these techniques allow reliable detection even when the received signal eye is closed by intersymbol interference, such as from polarization or chromatic dispersion. Finally, we discuss how these techniques can be integrated onto the detector IC for operation at 2.5 Gb/s and higher data rates. These techniques allow a single IC detector with adaptive nonlinear cancellation to be used in long-haul and undersea lightwave systems to optimize the detector threshold and compensate for the ISI due to such impairments as polarization and chromatic dispersion, nonideal receiver frequency characteristics, and transmitter/receiver mismatch.