Next-generation DWDM optical module based on PAM4 modulation

The next generation product forms based on PAM4 higher order modulation are: 50G (1x50G PAM4), 100G (2x50G PAM4) and 100G (1x100G PAM4).

DWDM (Dense Wavelength Division Technology) has experienced increasingly higher modulation rates, including 1.25G NRZ, 2.5G NRZ, 10G NRZ, and 25G NRZ, with 50G PAM4 and 100G PAM4 rates using higher-order modulation PAM4. Currently, the highly competitive DWDM coherent modulation technology is primarily used for 200G and 400G, with future support for 800G high-bandwidth services.

PAM4 DWDM optical modules can be inserted embedded DWDM systems and directly plugged into the appropriate data center routers or switches, eliminating the need for a separate DWDM converter platform, significantly reducing costs and simplifying deployment and maintenance. In addition, PAM4 modules can be added to existing DWDM networks for hybrid transmission, along with the appropriate dispersion compensation modules (DCM) and EDFA amplification systems.

The next generation product forms based on PAM4 higher order modulation are: 50G (1x50G PAM4), 100G (2x50G PAM4) and 100G (1x100G PAM4).

50G (1X50G PAM4) Program

Optical modules with 50G (1X50G PAM4) scheme is the 50G SFP56 DWDM optical module (C-band, 50Ghz wavelength spacing). This product is packaged in SFP56 , which has the same size as SFP+, and can be upgraded to 50G directly without changing the original deployment architecture. The module utilizes 50G PAM4 modulation on both optical and electrical side, and employs a DWDM EML laser on the transmitter side, which can meet the requirement of at least 80km transmission distance with the support of DCM dispersion compensation and EDFA. The total bandwidth of single fiber supports 96 waves x 50G = 4800G, and its industrial-grade temperature product form can meet the demand of 5G front transmission system.

100G (2X50G PAM4) solution

The optical module with a 100G (2X50G PAM4) scheme is the 100G QSFP28 DWDM optical module (C-band, 50Ghz wavelength interval), which is usually called 100G PAM4 QSFP28 in the industry. Its optical port carries 100GE service using 2 different 50G DWDM wavelengths. The electrical port side uses 4X25G NRZ, while the optical port side offers two options: CS interface and LC interface. The CS interface employs 2 inputs and 2 outputs, with a total of 4 fibers. On the other hand, the duplex LC interface option uses WDM multiplexing technology internally, and enabling transmission with only 2 fibers. With the addition of DCM dispersion compensation and EDFA(Erbium-Doped Fiber Amplifier), it can meet at least 80km transmission proximity requirements, and the total bandwidth of a single fiber supports 96 waves x 50G = 4800G.

100G (1x100G PAM4) solution

The optical modules with a 100G (1x100G) scheme are 100G QSFP28 DWDM optical modules (C-band, 100GHZ). This product is primarily realized by DWDM light source + silicon optical modulation technology. With the addition of DCM + EDFA, it meets 80km transmission distance requirement, and the total bandwidth of single fiber supports 48 waves x 100G = 4800G.

Due to its advantages, PAM4 DWDM optical modules are widely used in 100G and 400G constructions, such as point-to-point data center interconnect (DCI), DWDM-based 100G Ethernet metro access, campus and enterprise links, 5G mobile access architectures, etc. For application distances of 80km to 120km in data center DCI, the high-order PAM4 modulated 50G/100G DWDM based technology can compete for market share with the coherent 200G/100G DWDM technology, offering the advantage of low cost. As shown in the following table.