<title>Suboptimum bit synchronization in high-speed communications</title>

Abstract

In this communication we consider the use of a phase-locked loop with signal injection (PLLI) in clock synchronization circuits. We show that by exploring the correlation between the I (in- phase) and Q (quadrature) components of the disturbance, the PLLI allows significant improvements in the output jitter. Numerical results are given for optical communications with RZ signaling which show considerable improvements relatively to a conventional PLL. Experimental measurements obtained with a Colpitts VCO designed to allow current injection are presented that demonstrate the effectiveness of the PLLI in exploring the I-Q correlation.