Jitter is a measure of the short-term time variations of the significant instances of a digital signal from its ideal positions in time. If these variations are very slow (within 10 Hz as per ITU), they are known as wander. Jitter affects extraction of clock and network timing. Although receivers in OptSim™ do not use clock and data recovery (CDR) circuits, it is possible to analyze jitter-induced penalties using OptSim. The three main sources of jitter are: (i) system-related sources such as crosstalk, dispersion, reflections/interference; (ii) data-dependent sources such as intersymbol interference, duty-cycle distortion; and (iii) random noise in the system .
Total jitter at a given BER is an important performance metric for high-speed serial I/O links. Estimating total jitter from the bath-tub curves is one of the methods for the measurement of total jitter [2-5]. This article describes how to obtain a bath-tub curve in OptSim and ModeSYS™ to measure jitter.
Consider a sample topology layout for a serial link under test as shown in Figure 1. The transmitter sends 10 Gbps of data over 10 km standard SMF. To simulate the effect of jitter in decision time due to imperfections in the detector circuitry, the BER tester’s timingJitter parameter is set to introduce the root-mean-square (RMS) deviation  in time.