Passive CWDM vs. Active CWDM

Published on Updated on April 26, 2024

Wavelength division multiplexing (WDM) has emerged as a popular term in recent years. It is further distinguished into CWDM and DWDM. Of these, CWDM stands for Coarse Wavelength Division Multiplexing and DWDM for Dense Wavelength Division Multiplexing.

CWDM combines multiple laser beam signals of different wavelengths for fiber optic transmission on a single fiber. CWDM has fewer channels than DWDM and both these technologies are used to increase the bandwidth of fiber optic cables.

The multiplexing is conducted using a suitable multiplexer such as CWDM multiplexer and DWDM multiplexer. Of these, the CWDM SFP Modules are common multiplexing technology employed in telecom access, enterprise, and city networks.

This technology is further distinguished into passive CWDM and active CWDM. How do these passive and active components differ? Read the post to know the answers.

General Overview of Passive and Active CWDM Technology

A General Introduction to CWDM

Gaining a basic understanding of CWDM will help you understand active and passive sections better. The following pointers will be helpful in this case.

  • CWDM can transport up to 18 wavelengths between 1270 nm and 1610 nm over a single strand of fiber.
  • The wavelengths have a channel spacing of 20 nm and a channel width of 13nm.
  • This small channel spacing enables the utilization of cost-effective lasers.
  • CWDM technology is less expensive than DWDM technology, and it enables enterprise users to expand their networks without making big investments.

Passive CWDM and Active DWDM Described Briefly

Having known the CWDM technology, next comes the distinction between passive CWDM and active DWDM. This section introduces you to these terms and their effectiveness.

What Is Passive CWDM?

This technology uses no electric power, rather the wavelength separation is performed using prisms and bandpass filters. CWDM mux/demux is the type of passive CWDM device, and it can be used in servers, SDH, Ethernet devices, ATMs, TDMs, and so on. Today, most CWDM multiplexers found in the market are passive, and in recent years the demand for these devices has increased as manufacturers are trying to sell them to the home audience.

What Is Active CWDM?

As the name suggests, these devices use active components like muxponders and transponders. The devices of this type feature an active transport platform that can perform functions such as demarcation, signal monitoring, regeneration, and so on. This technology is used to connect ATM switches, routers, fiber optic network switches, and so on. The devices are more expensive than passive ones, which is why they are used by large enterprises and communication operators to transform or optimize their existing networks. Nowadays, active CWDM devices are widely used in metropolitan area networks (MANs).

Today, the performance of the fiber optic network is controlled by coarse wavelength division multiplexing (CWDM) techniques. It is important to understand this technology and its types better before investing in it. The previous post offered you brief insights on active and passive CWDM, while this post aims to help you with the right selection.

Passive CWDM vs. Active CWDM: Which One to Choose

As the basic differences between these technologies and devices powered by them may be clear now. There can be confusion regarding their selection. The pointers in this section will help you with the right selection.

Advantages of Passive CWDM

  • Easy Set-up: The technology uses fewer components, which makes the setup easy. The device usually is plug and play type, which makes the installation easy and requires no programming.
  • High MTBF Rates: It requires no cooling or power components, which makes it easy. The estimated mean time between failures (MTBF) of passive CWDM components is 500 years. MTBF predictions are usually made to address the failure rates of different components in a device.
  • Independent and Flexible: Unlike other WDM technologies, passive CWDM is independent of any transmission speed as well as protocols, which further simplifies its use. Owing to its transparent and independent nature, the CWDM multiplexer can accommodate a wide range of technologies across various channels on the same fiber.
  • Cost-effective Solution: Data can be transmitted over 18 channels in a single fiber strand up to 40 km, which helps make annual savings of $4K-$72K in city networks, and from $1 to $22K in enterprise networks.

Disadvantages of Passive CWDM

  • The passive CWDM multiplexers use optical transceivers, which make the devices expensive.
  • The multiplexers of this type possess limited link power budget and distance, and its simple to use design makes performance monitoring difficult.
  • CWDM optics in the multiplexer is difficult to monitor and manage, which is perceived as a major obstacle while implementing this device.

Advantages of Active CWDM

  • Enables Short Range to Long Range Conversion: They are standalone DC or AC powered components, which are separated from the system. They usually take the short-range optical output of the switch as input and convert them into long-range WDM signal. This conversion is enabled by a transponder and the converted signal is fed to multiplexers and transceivers.
  • Cost Efficient: Unlike passive CWDM, the active CWDM uses cheaper optics, which makes them affordable. Possessing muxponder capabilities, these devices form the backbone of enterprise networks. Muxponder capabilities mean mapping multiple wavelengths on a single fiber. This significantly helps reduce the operating costs.
  • Additional Revenues: This CWDM infrastructure allows service providers to deliver managed services to their customers and business partners and earn additional revenues.
  • Flexibility: Like passive CWDM, active CWDM also offers a certain level of flexibility. One can add or improve the capabilities and attempt traffic regeneration at multiple points within the infrastructure.

Disadvantages of Active CWDM

  • Although the separation between the systems from the actual switch enables long-range conversion, it also makes the fiber optic network switches network system more complex.
  • There are several components involved in an active configuration, which may make troubleshooting a bit complex.
  • This configuration requires a serious and in-depth understanding of optical networks.

What is CWDM?

CWDM stands for Coarse Wavelength Division Multiplexing. It is a technology used to combine multiple optical signals onto a single fiber optic cable by assigning different wavelengths of light to each signal. CWDM typically operates at a wavelength range of 1270nm to 1610nm and supports up to 18 channels. It is commonly used in applications such as campus networks, storage area networks (SANs) and video distribution.

What is DWDM?

DWDM stands for Dense Wavelength Division Multiplexing. It is a technology used to transmit multiple optical signals simultaneously over a single fiber optic cable. This is done by assigning different wavelengths of light to each signal. DWDM typically depends on the network's specific needs and requirements on whether to utilize CWDM or DWDM. Has a wavelength range of 1530nm to 1565nm and supports up to 80 channels. It is commonly used in applications such as long-distance data transmission, metro networks and telecommunications.

CWDM vs DWDM: What Are Their Differences?




Wavelength spacing

20 nm

0.8 nm


Up to 18

Up to 96 or more


Up to 40 km

Up to 400 km or more


Generally more cost-effective

More expensive


Less precise and forgiving

More precise and expensive to maintain


Shorter distances or smaller networks

High-capacity applications over longer distances

Knowing the differences between passive CWDM and active CWDM is not enough to realize their benefits. It is important to choose high-quality CWDM multiplexers if you wish to scale your existing fiber optic network. Owing to their increasing use, today, it is easy to find these devices from different brands. VERSITRON, a leading manufacturer of fiber optic products in the US, also provides CWDM multiplexers in different specifications. The company also provides different types of fiber optic products such as ethernet media converters, network switches, fiber optic modems, and so on. These products have been part of robust fiber optic networks for several years now.

Rich Tull

Rich Tull
R.W. Tull is the President of Versitron, a leading technology company specializing in data communication and networking solutions. With expertise in Guiding network switches and media converters, R.W. Tull has played a pivotal role in driving Versitron's success. His deep understanding of these technologies has enabled the company to provide innovative and reliable solutions to clients. As a visionary leader, He ensures that Versitron remains at the forefront of the industry, delivering cutting-edge networking solutions that enhance data communication efficiency.
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