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.
Figure 1: Comparison of Waveforms between NRZ and PAM4 Signals
The form factor in which 100G DWDM transceivers utilize PAM4 is QSFP28. Next, let's dive into how PAM4 DWDM QSFP28 supports 100G/400G applications.
How Does PAM4 QSFP28 Perform As a Solution for 100G/400G?
As a quite capable alternative for extending 100G/400G signals, QSFP28 PAM4 has recently become a trending product for network operators. Here are the benefits of adopting QSFP28 DWDM PAM4 in 100G/400G applications:
Large Data Capacity
QSFP28 PAM4 DWDM can provide up to 4.8Tb/s of data capacity over single-mode fiber (SMF) and minimize signal degradation. It can be used for 100G/400G extensions between data centers with point-to-point links and transmission distance of up to 80km.
Power Power Consumption
It is designed to offer a lower power consumption for high-speed extended reach data center interconnects (DCI) and high-density connectivity.
Pluggable with embedded DWDM, the PAM4 DWDM transceiver can be inserted directly into the appropriate data center routers or switches without the need of a separate DWDM converter platform, significantly reducing the cost and simplifying the deployment and maintenance. Moreover, with the right dispersion compensation modules (DCMs) and amplification system in place, QSFP28 PAM4 modules can be added to an existing DWDM network to achieve a hybrid transmission.With all the benefits it provides, QSFP28 PAM4 DWDM modules are often adopted for 100G and 400G construction, such as point-to-point data center interconnects (DCI), 100G Ethernet metro-access over DWDM, campus and enterprise links, 5G mobile access architecture, etc.
Figure 2: PAM4 Applications in Data Centers and 5G Architecture
For 100G transceiver modules, QSFP28 PAM4 can reduce the number of lasers and eliminate the need for optical multiplexing. For 400G, the largest expenditure would be optical components and related radio frequency packages. PAM4 can transmit two bits of logic information and double the bandwidth to effectively reduce the transmission costs and at the same time, meet the needs of bandwidth improvements.
3C-LINK 100G DWDM QSFP28 PAM4 Solution
Based on the bandwidth demands of global users, 3C-LINK provides 100G DWDM QSFP28 PAM4 solution integrated with DWDM QSFP28 PAM4 transceiver and fiber cables to achieve high-speed signal transmission and the construction of 100G.
Figure 3: 3C-LINK QSFP28 PAM4 Solution--100G DWDM QSFP28 PAM4 120km DOM CS
Featuring low power consumption, high speed and long transmission distance, QSFP28 PAM4 would be the most cost-effective and efficient solution for data centers or campus and enterprise links to upgrade their networks into 100G/400G.