PAM4 vs. NRZ: What You Need to Know
So you’ve been thinking about PAM4 vs NRZ and want to know how these two vary and how PAM4 will affect the optical communication industry. For starters, Pulse Amplitude Modulation 4-level, abbreviated as PAM4, was already recognized by microwave link technicians around the turn of the century. Modern microwaves, for example, employ substantially greater modulations, even up to 1024QAM. PAM4 is, in our opinion, just the beginning of signal modulation applications in the optical industry. We anticipate that, like in the microwave business, greater and higher modulation techniques will be implemented in optical communications. PAM16 would be the next in line.
PAM4 allows to double the amount of transmitted information in the same baud rate
To put it simply, PAM4 has a significant advantage over NRZ in terms of data transfer capacity. At the same baud rate, PAM4 doubles the quantity of information that may be conveyed. In other words, if NRZ can send one bit per baud unit, PAM4 can broadcast two bits per unit. The term comes from the fact that the signals may be modulated to four distinct amplitudes.
SNR (Signal-Noise Ratio), on the other hand, drops as distance increases. It is most observable with PAM4 modulation. A greater SNR value is required for higher power levels. As a result, PAM4 modulation is currently more widely applied for short-distance connections. Transceivers that are based on PAM4 technology require more accurate, synchronized, and equalized Tx/Rx components. For example, DSP (Digital Signal Processor) improves Tx/Rx component performance by synchronizing and equalizing signals. That’s why PAM4 transceivers, such as QSFP56, QSFPDD, nowadays are more costly than previous generation NRZ-based transceivers.
To summarize, PAM4 vs NRZ – PAM4 in the optical industry is still a new technology, which has to mature. But as with any new technology, it will become a common occurrence and will be much more accessible and suitable for the desired solutions. Finally, visit our more detailed explanation of PAM4 here: 100G Single Lambda (100G PAM & Single Lambda).
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200G QSFP56 Modules
While 100G transceivers (especially QSFP28 form factor ones) are well known and used on a large scale in the optical industry, the demand for higher capacity interconnections is growing. 200G QSFP56 (Quad Small Form-Factor Pluggable 56) transceivers are here to address the challenge. While QSFP56 transceivers use the same physical specifications as the QSFP28 form factor and still have 4 electrical lane signals (same as QSFP28), but instead of carrying 4x25G NRZ modulated signal (QSFP28), QSFP56 transceivers support 4x50G PAM-4 (Pulse Amplitude Modulation 4-level) signals, which effectively doubles the network’s data rate to 200G. Our 200G QSFP56 portfolio consists of transceivers which can operate over Single-Mode Fiber (SMF) or Multi-Mode Fiber (MMF), can be used for connection distances from a couple of meters up to 2 kilometers and can support up to 212.5 Gbps data rate, thus 200G Ethernet application. 200GBASE-SR4 (PN: 200G-QSFP56-100) module is used for short distance interconnection (up to 100 meters with FEC) and have MTP/MPO 12 Connector, while 200GBASE-FR4 (PN: 200G-QSFP56-2.1) is used for connection distances up to 2 kilometers and have double LC connector. One of the most typical applications for 200G QSFP56 modules is interconnecting two 200G QSFP56 modules to make 200G Ethernet link or to connect two 200G QSFP56 to 400G QSFP56-DD or 400G OSFP form factor modules in a breakout scenario. For 400G breakout to 2x200G typical would be 400GBASE-2FR4 breakout to 2 x 200GBASE-FR4 signals, or 400GBASE-SR8 breakout to 2 x 200GBASE-SR4 signals. Need to note that to be able to make 400GBASE-2FR4 breakout to 2 x 200GBASE-FR4, special CS patch cables are required as 400GBASE-2FR4 modules are equipped with double CS connectors. Above described connections are popular in Data Centers where we have many 200G interfaces coming from the server side (NICs) which need to be aggregated by the Data Center switch. Our 200G QSFP-56 portfolio complies with CMIS 4.0 Management interface specification, electrical interface comply with 200GAUI-4 (IEEE 802.3bs) and optical interface comply with 200GBASE-SR4 optical specifications, where hardware is compliant with SFF-8679 QSFP+ 4X Hardware and Electrical Specification. 200G QSFP56 modules are widely used in Mellanox, Intel Network cards, Arista, Huawei Data Center switches and other industry well known manufacturers equipment. 200G QSFP56 transceiver can work in 80% of networking equipment, where there is no special algorithm for protection against third party modules. However – we have accumulated expertise in custom-encoded firmware for 200G QSFP56 in order to make these modules work in almost any brand of equipment. We will be glad to know your requirements – Contact Us.
400G QSFP-DD Optical Transceivers
Unlock next-level performance with 400G QSFP-DD modules, engineered for high-density, high-speed data transmission in modern data centers. With double-density architecture, QSFP-DD supports 400G in a compact form, providing efficient scalability and optimal power usage for next-gen network demands. Our 400G QSFP-DD portfolio offers connectivity from short to long range. Here you will also find the 400G QSFP-DD Coherent section for high-speed data transfer, and ultra-reliable connectivity. Explore how 400G QSFP-DD technology is powering innovation and enabling the next era of connectivity across industries.