Overview of 100G PAM4 Optical Modules with DWDM Technology
May 13, 20251 min read
With the rapid growth of big data, cloud computing, AI, and 5G, modern networks—especially in medium-to-long distance transmission scenarios—are facing increasing demands for high-speed, high-capacity data transmission. In this context, the 100G DWDM PAM4 optical module, which combines the advantages of PAM4 modulation and DWDM technology, becomes an ideal solution. This article will explore the definition, features, advantages, application scenarios, and FS product highlights of 100G PAM4 DWDM optical modules, helping you understand their key role in high-bandwidth network deployments.
What Are 100G PAM4 DWDM Optical Modules?
100G PAM4 DWDM Optical Modules Definition
100G DWDM PAM4 optical modules are high-performance optical transceivers that utilize PAM4 and operate on DWDM channels within the C-band spectrum. They support 100Gbps transmission over a single wavelength, significantly improving spectral efficiency while maintaining compatibility with long-reach optical networks. Typically built in the QSFP28 form factor, these modules are optimized for applications such as data center interconnect (DCI), metro transport, and 5G backhaul, where both bandwidth density and transmission distance are critical.
Working Principle of 100G PAM4 DWDM
100G PAM4 DWDM modules combine two advanced technologies—PAM4 and DWDM—to achieve high-capacity, long-distance data transmission over a single optical fiber.
PAM4 Modulation
Unlike traditional NRZ which carries 1 bit per symbol using two signal levels, PAM4 uses four distinct amplitude levels to encode 2 bits per symbol. This effectively doubles the data rate without increasing the signal bandwidth, making it ideal for 100G transmission within the same optical spectrum.
DWDM Multiplexing
DWDM allows multiple data streams, each assigned a unique wavelength (or channel), to be transmitted simultaneously over a single fiber. A 100G DWDM PAM4 module typically operates at one wavelength and is combined with other wavelengths using multiplexers to form a composite signal.
Transmission & Reception
At the transmitter, data is modulated with PAM4 and transmitted through a laser tuned to a specific wavelength. On the receiver side, the signal is demultiplexed and the PAM4 data is decoded using high-speed DSP (Digital Signal Processing) to recover the original bitstream.
This combination enables high spectral efficiency, cost-effective scaling, and long-reach transmission.
Advantages of 100G PAM4 DWDM Optical Modules
In DWDM applications where high bandwidth and efficient spectrum usage are crucial, 100G QSFP28 PAM4 DWDM optical modules offer a highly competitive solution by balancing performance, cost, and scalability.
Maximized Spectral Efficiency for DWDM Systems
Using PAM4 modulation, these modules achieve 100G transmission over a single DWDM wavelength within the C-band, significantly improving spectral utilization. Compared to traditional NRZ modulation, PAM4 enables lower baud rates for the same data throughput, reducing signal distortion and allowing for longer transmission distances—typically up to 80 km—with the help of EDFA and DCM. This makes PAM4-based DWDM ideal for high-density wavelength applications in metro and DCI networks.
Cost-Effective Alternative in DWDM Deployments
Unlike coherent DWDM modules that rely on expensive DSP chips and consume more power, PAM4 100G DWDM modules use simpler optics and electronics. This not only lowers production and operating costs but also eliminates the need for additional transponder equipment, making them a more economical choice for short to medium-range DWDM deployments.
High Integration and Port Density for Dense Networks
Encapsulated in a compact QSFP28 form factor, PAM4 100G DWDM modules support high port density, which is essential for maximizing rack space in data centers and metro nodes. Their small size simplifies DWDM system design while enabling scalable capacity upgrades without major infrastructure changes.
Flexible Compatibility with Existing DWDM Infrastructure
Supporting common interfaces such as LC and CS, these modules are compatible with standd MUX/DEMUX and ROADM systems. They can be easily integrated into existing DWDM networks for services like point-to-point DCI, 5G fronthaul, and metro Ethernet, offering a seamless upgrade path toward higher bandwidth.
In summary, QSFP28 PAM4 DWDM optical modules provide an efficient and practical solution for DWDM networks, especially in scenarios requiring high wavelength density, low cost, and flexible deployment.
Building on the inherent advantages of 100G PAM4 DWDM modules, FS further enhances their practical value in DWDM applications through rigorous testing and high-quality components. The FS 100G PAM4 DWDM optical module features a Broadcom chipset and a maximum power consumption of just 7W. It supports Digital Optical Monitoring (DOM), enabling efficient network maintenance. Compliant with IEEE 802.3bm and QSFP28 MSA standards, the module is hot-pluggable and meets Class 1 laser safety and RoHS environmental standards.
Each module is tested on major-brand switches to ensure seamless integration and stable operation within existing DWDM systems. It supports multiple services over a single duplex DWDM fiber link, with transmission distances of up to 80 km (with EDFA and TDCM), making it ideal for various DWDM deployment scenarios. FS offers a high-performance, scalable, and cost-effective solution tailored for next-generation DWDM networks.
Disadvantages of 100G PAM4 DWDM Optical Modules
While 100G PAM4 DWDM modules offer advantages such as higher density and lower cost, they also present several limitations in dense wavelength division multiplexing (DWDM) environments:
High OSNR Requirements
PAM4 modulation is more sensitive to optical signal-to-noise ratio (OSNR) compared to traditional NRZ. In DWDM systems where multiple wavelengths share a single fiber and amplifier noise accumulates, PAM4’s lower noise tolerance can lead to increased bit error rates (BER). This results in tighter requirements for link design and reduced margin for signal degradation.
Lower Spectral Efficiency
Although PAM4 increases the data rate, it requires wider channel spacing—often 50GHz or more. In contrast, coherent optics can operate with narrower spacing or flexible grid configurations, offering better spectral efficiency. This limits PAM4’s scalability in high-density DWDM systems where maximizing wavelength utilization is critical.
Sensitive to Impairments
PAM4 signals are more vulnerable to chromatic dispersion, non-linear effects, and power imbalance. In DWDM applications, this necessitates precise link engineering, including the use of EDFAs and TDCMs for signal amplification and dispersion compensation. The added complexity increases both deployment and operational challenges.
Limited Long-Haul Transmission Capability
Without coherent detection, QSFP28 PAM4 DWDM modules typically support transmission distances up to 80 km with the aid of amplification and dispersion compensation. This makes them suitable for metro networks and data center interconnects (DCI), but less ideal for long-haul or backbone network scenarios where coherent solutions offer superior performance.
In summary, while 100G PAM4 DWDM modules provide a cost-effective and compact solution for certain applications, their performance in DWDM systems is constrained by noise sensitivity, limited spectral efficiency, and shorter reach. Careful link planning and system design are essential to ensure reliable operation.
Differences Between 100G PAM4 DWDM and Coherent Transceivers
In DWDM solutions, in addition to 100G PAM4, coherent modules are also quite popular. So, what are the key differences between them? After understanding the basic concepts and advantages of QSFP28 PAM4 DWDM modules, we will now compare the main differences between 100G PAM4 DWDM modules and coherent optical modules to help you better choose the most suitable solution for your specific application.
Performance Parameters Comparison
Feature | 100G PAM4 DWDM | 100G Coherent DWDM |
Modulation Format | PAM4 | QPSK/16QAM and other advanced modulation schemes |
Transmission Distance | Up to 80 km (with EDFA & DCM) | >1000 km with advanced DSP |
Spectral Efficiency | Moderate | Higher |
OSNR Tolerance | Lower | High OSNR tolerance |
Power Consumption | Lower | Higher |
Cost | More affordable | Significantly higher |
Integration | QSFP28 form factor, compact | Larger modules (e.g., CFP2-DCO) |
Deployment Complexity | Simpler, pluggable | Requires transponders and specialized platforms |
Application Suitability
PAM4 modules are ideal for cost-sensitive, short-to-medium distance DWDM deployments such as data center interconnects (DCI), metro networks, and 5G front-haul.
Coherent modules are preferred in long-haul backbone, international links, and dynamic DWDM networks with ROADMs.
In summary, 100G PAM4 modules are ideal for short- to medium-distance scenarios due to their high cost-effectiveness, while coherent modules are better suited for complex, long-distance, and highly flexible network requirements thanks to their superior transmission performance. When making a choice, it’s important to consider multiple factors.
Conclusion
In conclusion, the 100G PAM4 DWDM optical module is a high-performance, cost-effective solution for modern networks. Offering high speed, low latency, and energy efficiency, it is perfect for data centers, 5G networks, high-performance computing, and enterprise upgrades. As network demands continue to grow, FS ensures reliable, scalable modules that support your infrastructure and enable next-generation connectivity. Whether you choose the QSFP28 PAM4 DWDM module or another WDM optical modules, FS is committed to delivering top-tier products that enhance your network’s performance and scalability.
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- Optics and Transceivers
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