A Simple Method of Jitter Evaluation for Designing Phase-Locked Loops for Optical Communication Systems

A simple method for evaluating jitter generation is proposed for phase-locked loops (PLLs) applied to optical communication systems. The precise but complex expressions in the conventional method involving the phase noise of the voltage-controlled oscillator, the jitter-transfer function of the PLL, and integration using a filter function are greatly simplified with the objective of providing a simple estimate of the jitter generation avoiding iterative design procedures. These simplifications together with the data from the International Telecommunication Union (ITU)-T Recommendations lead to an integral-free expression with only a small number of parameters, which enables jitter evaluation using a hand-held calculator. By applying bandwidth limits to the jitter tolerance and transfer specifications, both the sufficient and insufficient conditions for the phase noise of a voltage-controlled oscillator are obtained to enable the efficient design of a PLL with the jitter generation specified in the ITU-T Recommendations.