Jitter Margin Analysis of 56-Gb/s $\text{PAM}4\times 8-\text{Channel}$ VCSEL-Based Optical Transceiver for Co-Packaged Optics

We evaluate an optical link employing an ultra-compact 850-nm MM VCSEL-based 56-Gb/s $\mathbf{PAM}\mathbf{4} \times \mathbf{8}-\mathbf{channel}$ optical transceiver and three different kinds of MMFs (i.e., OM3, OM4, and OM5 fibers). We particularly analyze jitter margin characteristics for serial and 8-channel parallel signal transmissions. TDECQ values are also measured for optical eye diagrams transmitted through MMFs of several different conditions. The measured TDECQ values are as small as <1.9 dB within the specified distances of MMFs based on IEEE802.3cm. Jitter margin characteristics at the KP4-FEC threshold (i.e., BER of $\mathbf{2}.\mathbf{4}\times \mathbf{10}^{-\mathbf{4}})$ are narrower as increasing the distance of OM4, but a jitter margin of $\geq \mathbf{0}.\mathbf{35}$ U.I. can be kept within 110 m. We also measure no jitter margin degradation between serial and 8-channel parallel signal transmissions.