100G DWDM QSFP28 PAM4 120km Solution
PAM4, also referred to as Pulse Amplitude Modulation 4-level, is one of the mainstream optical transmission technologies following non-return-to-zero (NRZ). PAM4 is a technology encoding two bits of data with four distinct signal levels. It essentially doubles the signal bandwidth of a connection with each signal level representing 2 bits of logic information. In addition, as a key role in multi-order modulation, it can minimize optical signal degradation while doubling the data rate, which makes it the most efficient and cost-effective enabler of 100G and 400G. To make it more specific, check the following figure to see how PAM4 doubles the data rate with four signal levels by comparing it with NRZ