Today, all digital activities rely on high-speed transmission infrastructure to carry massive amounts of data: from internet traffic and OTT services to artificial intelligence (AI), cloud computing, and high-resolution video. As such, expanding optical network capacity has become a critical mission for telecom operators, enterprises, and regulators worldwide.
In this context, Wavelength Division Multiplexing (WDM) optical transmission technology—particularly its two main variants, Coarse WDM (CWDM) and Dense WDM (DWDM)—has emerged as a strategic solution to scale transmission capacity without the need for additional physical fiber infrastructure.
WDM allows multiple optical signals to be transmitted over a single fiber by using different wavelengths of light, akin to having multiple lanes on a highway for different types of signals to travel in parallel without interference. This is a major leap beyond traditional optical transmission, which could only carry one signal at a time. WDM is categorized into two main types: CWDM and DWDM. Both leverage the principle of multi-wavelength transmission but differ in channel density, deployment cost, and application scope.
CWDM (Coarse Wavelength Division Multiplexing) uses wider wavelength spacing—typically 20 nanometers apart—and supports up to 8 to 18 channels on a single fiber. With broader wavelength separation, CWDM equipment is simpler, consumes less energy, and is more cost-effective. It offers key advantages in affordability and ease of deployment, does not require cooling for laser transmitters, and is energy-efficient. CWDM is particularly suited for short to medium distances—typically under 80 kilometers—making it ideal for connecting office branches, metropolitan area networks (MANs), and networks in industrial parks or high-tech zones.
DWDM (Dense Wavelength Division Multiplexing), by contrast, uses tightly spaced wavelengths—approximately 0.8 to 1 nanometer apart. This allows for 40 to over 160 channels on a single fiber, with each channel capable of speeds ranging from 10 Gbps to 400 Gbps, and even up to 800 Gbps depending on equipment configuration. DWDM is designed for extremely high-capacity and long-haul transmission—extending over thousands of kilometers with the help of optical amplifiers such as EDFA (Erbium-Doped Fiber Amplifier). DWDM is the preferred technology for data center interconnects (DCIs), national and international backbone routes, and integrates seamlessly with existing fiber infrastructure without the need to replace physical cables. While DWDM requires higher initial investment than CWDM, it offers superior long-term efficiency and scalability.
Choosing between CWDM and DWDM depends on the specific needs of each organization. If a business requires an economical solution for moderate bandwidth over short distances, CWDM is a suitable choice. Conversely, for large-scale capacity expansion, high stability, and long-distance transmission, DWDM is the optimal solution. In many cases, telecom operators or large data centers adopt a hybrid approach, combining both technologies to optimize cost and performance across different network layers.
In Vietnam, the surge in digital services such as high-definition video, cloud computing, AI-powered services, and the rapid development of data centers and international cable routes are creating an urgent need for transmission capacity expansion. Laying additional fiber or building new infrastructure is costly and time-consuming. Therefore, CWDM—and especially DWDM—are seen as effective solutions to enhance bandwidth while significantly reducing investment costs. Major telecom operators in Vietnam have begun deploying DWDM on the North–South backbone and for international connections to Singapore, Hong Kong, and the U.S., marking an important step in ensuring transmission capabilities for digital services in the new era.
Looking ahead, as technologies like AI, IoT, smart cities, and virtual reality grow exponentially, bandwidth demand will continue to rise without limit. Early investment in modern optical transmission solutions such as CWDM and DWDM not only optimizes current operations but also lays a strong foundation for the nation’s telecommunications system for the next 10–20 years. In a world where data is the most valuable resource, having a flexible, efficient, and scalable transmission infrastructure is a key competitive advantage for every business and country.