Eye don't like it

摘要

My heart sank when I first saw the hideous jitter and loss of noise margin evident in the eye diagram of Figure 1. The figure shows the received eye diagram for a simple serial connection operating at 2.5 Gbps. This differential link connects a fiber-optic receiver module (O/E) to a large protocol processing chip (PHY). The figure illustrates the signal measured with a high-bandwidth differential probe at the receiving end of the link (Figure 2). Data goes from left to right in the picture.