Next-Generation DWDM Optical Modules Based on PAM4 Modulation

The latest report, encompassing the second quarter of 2023, highlighted a 5% year-on-year growth in revenue for optical transport equipment, reaching slightly over $4.0 billion. The consistent growth rate for the optical market over the past three quarters was attributed to higher DWDM long haul and multiservice multiplexer revenue, surpassing initial estimates.

Let’s delve further into DWDM technology. Dense Wavelength Division Multiplexing (DWDM) technology has seen a rise in modulation rates, ranging from 1.25G NRZ to 25G NRZ, incorporating high-level modulations like 50G PAM4 and 100G PAM4. Additionally, competitive DWDM coherent modulation is aiming at 200G, 400G, and future 800G high-bandwidth services.

PAM4 DWDM optical modules can seamlessly integrate into embedded DWDM setups, directly connecting to compatible data center routers or switches without the need for a separate DWDM transceiver platform. This integration significantly reduces costs and simplifies deployment and maintenance. Furthermore, the utilization of appropriate dispersion compensation modules (DCM) and EDFA amplification systems enables the incorporation of PAM4 modules into existing DWDM networks for hybrid transmission.

The next-generation product lineup based on high-level PAM4 modulation includes 50G (1X50G PAM4), 100G (2X50G PAM4), and 100G (1x100G PAM4).

50G (1X50G PAM4) Solutions

Optical modules following this approach, such as the 50G SFP56 DWDM optical modules (C-band, 50GHz wavelength interval), adopt SFP56 packaging to maintain compatibility with SFP+ sizes, allowing direct upgrades to 50G without altering initial deployment structures. Employing 50G PAM4 modulation on both optical and electrical fronts, utilizing DWDM EML lasers on the transmit end, this setup, fortified with DCM and EDFA, meets transmission requirements for distances exceeding 80km. Its single-fiber total bandwidth of 96 waves x 50G = 4800G, coupled with an industrial-grade temperature form, aptly caters to 5G fronthaul system needs.

50G SFP56 DWDM Optical Module Schematic

100G (2X50G PAM4) Solutions

Optical modules utilizing the 100G (2X50G PAM4) approach include the 100G QSFP28 DWDM optical module (C-band, 50GHz wavelength interval). Commonly referred to as the 100G PAM4 QSFP28 in the industry, this module carries 100GE services through two distinct 50G DWDM wavelengths. The electrical side employs 4X25G NRZ, while the optical side offers two options: CS and LC interfaces. The CS interface uses 2 in and 2 out, utilizing 4 optical fibers, whereas the duplex LC interface internally employs WDM multiplexing technology, achieving transmission with only 2 fibers. With DCM dispersion compensation and EDFA amplification, it can meet transmission requirements for distances of at least 80km. Single-fiber total bandwidth supports 96 waves x 50G = 4800G.

100G QSFP28 DWDM Optical Module (CS Interface) Schematic
100G QSFP28 DWDM Optical Module(LC Interface) Schematic

100G (1x100G PAM4) Solutions

The optical modules adopting the 100G (1x100G) approach include the 100G QSFP28 DWDM optical module (C-band, 100GHz). This product primarily utilizes DWDM light sources and silicon photonics modulation technology. With the support of DCM+EDFA, it meets transmission requirements for 80km distances, and the single-fiber total bandwidth supports 48 waves x 100G = 4800G.

100G QSFP28 DWDM Optical Module Schematic

PAM4 DWDM optical modules, leveraging their advantages, are typically employed in 100G and 400G deployments, such as point-to-point Data Center Interconnect (DCI), DWDM-based 100G Ethernet metropolitan access, campus and enterprise links, and 5G mobile access architecture. For applications requiring 80km to 120km distances in data center DCI, leveraging the cost advantages of high-level PAM4 modulation 50G/100G DWDM technology, they can competitively secure market share against coherent 200G/100G DWDM technologies. As shown in the table below:

50G PAM4 DWDM system VS 100G PAM4 DWDM system VS 100G DWDM coherent system


As an Open Optical Network Mail Carrier, FIBERSTAMP is committed to providing global users with Economic, Professional and Efficient Open Optical Network Solutions. The current main products cover 25G/50G/100G/200G/400G optical transceiver modules, Active Optical Cables (AOCs) and Direct Attached Cables (DACs), 100G/200G/400G coherent optical modules and UHD video transmission products. Meanwhile, through long-term deep digging in new technology, FIBERSTAMP is rapidly evolving to the promising era of 800G and CPO based on Silicon Photonics!