CWDM (Coarse Wavelength Division Multiplexing)

CWDM (Coarse Wavelength Division Multiplexing)


CWDM (Coarse Wavelength Division Multiplexing)

Coarse wavelength division multiplexing (CWDM) is a popular technology that can be used to add capacity to a network without replacing it. CWDM is typically used for lower cost, sub-10G applications that are not intended to support high-bandwidth services.

CWDM is based on 20-nm channel spacing in the 1470 to 1610 nm spectrum, typically deployed on fiber spans up to 80 km. This wide spacing of channels allows the use of moderately priced optics, but the capacity and distance supported are significantly less than those of DWDM.


CWDM (Coarse Wavelength Division Multiplexing) is one of the most cost-effective technologies that telecom companies can use to expand their network capacity and increase data rate. The technology modulates different wavelength laser beams with a large number of signals, maximizing the utilization of fiber optic cable to transmit and receive a large amount of data at minimal costs.

Unlike DWDM, which is used more often for high-capacity data transport needs, CWDM can also be deployed in low-capacity or short-range applications that do not require long distances or spectral efficiency. It is ideal for metropolitan area networks, enterprise networks, and telecom access networks where cost is a primary consideration.

The technology is based on 20-nm channel spacing in the 1470 to 1610 nm spectrum. Compared to DWDM, which is deployed in the much narrower 1530 to 1570 nm spectrum, CWDM devices can operate with lower power dissipation and less thermal management. It requires a fraction of the number of lasers, transponders, optical amplifiers, and optical filters required in DWDM systems, which can lead to lower overall system costs.

Another key advantage of CWDM is the fact that it can be used to map DWDM channels onto a single fiber pair, allowing carriers to scale their network capacities and increase traffic speeds without changing the existing fiber infrastructure between their network sites. This feature is especially important in metro networks where fiber is at a premium, as it can save on network maintenance and operating costs.

CWDM is becoming more popular as carriers seek cost-effective solutions for their transport needs. This is because it can offer the same functionality and low end-to-end latency that DWDM offers, while being smaller and less expensive than DWDM, and utilizing uncooled distributed-feedback lasers and wideband filters instead of thermoelectric coolers and dispersion compensators.

It can be easily configured for a variety of network topologies. For example, it can be configured for point-to-point connections or point-to-multipoint connections for fiber rings or add/drop application. Moreover, it can be converted into an active configuration, which allows the operator to improve its capabilities and attempt traffic regeneration at different points within their network infrastructure.


CWDM technology is a flexible solution for expanding fiber network capacity. It can be deployed on most types of fiber networks and is commonly used in point-to-point topology in enterprise networks and telecom access networks. DWDM, on the other hand, is typically deployed in metropolitan network ring topology and interconnecting data centers and financial services networks.

DWDM is a more complex system than CWDM because it requires more wavelengths to be spaced closely together in order to fit the entire 1550 nm C-Band spectrum into a single fiber. DWDM supports 96 channels, each with 0.8 nm channel spacing. This enables it to transmit large amounts of data across a single fiber.

Both CWDM and DWDM offer a variety of advantages over traditional single-mode fiber, including cost savings, increased bandwidth capacity, higher speed, and greater flexibility. They also allow for easy upgrade and expansion to meet the growing demands of data-hungry applications such as cloud computing and mobile devices.

However, both technologies have their limitations. CWDM is more economical and suitable for shorter-range communications, while DWDM has greater bandwidth capabilities but can be more expensive. It can also be difficult to deploy CWDM in a metro area because it doesn’t support high-density ONUs and requires more power.

Additionally, DWDM is more complex than CWDM and can be difficult to set up. A typical DWDM system consists of several modules and multiple strands of fiber to carry the wavelengths, and a single module can connect to many different sources. This complexity can make it more difficult to install and maintain than a CWDM solution.

Another important difference between CWDM and DWDM is the ability to change the number of channels in the system. With CWDM, operators can change the number of wavelengths that are transmitted by adding more modules to their network. They can also replace individual CWDM transceivers to increase their capacity.

The ability to add and remove CWDM is an cwdm invaluable feature for metro network operators who want to provide a high-quality and flexible transmission platform to their customers. This is especially important in ESCON and FICON/Fibre Channel-based SAN applications where wavelength re-use and low end-to-end latency are critical.


CWDM provides high-performance and reliable transmission for LAN and SAN networks. With its abundant network topology, CWDM is used to interconnect geographically dispersed LANs and SANs (local area network and storage area network).

In addition to providing higher-speed data transmission, DWDM offers better network reliability because it eliminates optical amplifiers. Amplifiers are expensive, generate extra noise and can cause power balancing and gain tilt issues in optical fibers. They can also affect the performance of a link and may lead to system failure.

Another important consideration is insertion loss. MUXes with low insertion losses can reduce the number of optical amplifiers needed to transmit data, making them more cost-effective. However, if the insertion loss changes over time, the resulting interference can disrupt network operation.

A common problem in DWDM systems is a single channel failure. This could be the result of a transmitter going dark or an electrical failure in a fiber cable connector.

Optical signal analysis tools such as an OSA can provide detailed information on individual channels to help identify the source of the failure. They also offer the ability to test all points along a DWDM link, making them essential troubleshooting instruments in the event of a system failure.

In addition to the insertion loss, other MUX characteristics that impact system reliability include filter profiles and thermal properties. These features can influence a link’s power budget, the amount of optical amplifiers required and the number of wavelengths in a given channel.

The insertion loss is particularly important because it can affect the amount of energy that the link can carry, and a higher insertion loss will make the link more sensitive to environmental conditions. The higher the insertion loss, the lower the output power will be.

One of the key factors in determining a CWDM system’s insertion cwdm loss is the fiber length. Using shorter fibers can decrease the insertion loss and increase the maximum optical power that a DWDM link can deliver.

For more information on a reliable CWDM solution, contact us today. We’ll be happy to provide you with the details and answers you need!


Coarse Wavelength Division Multiplexing (CWDM) was first introduced in the 1990s as a lower cost alternative to dense wavelength division multiplexing (DWDM). CWDM transmits several wavelengths/colors of light through a single fiber. In this way, it increases the bandwidth of a fiber optic system.

The CWDM spectrum ranges from 1270 nm to 1610 nm in 20-nm increments. In the CWDM O-band, transmissions are centered around eight wavelengths: 1470 /1490 /1510 /1530 /1550 /1570 /1590 /1610. The E-band and S+C+L-band are also possible by adding 10 additional channels from 1370 nm to 1611 nm with a further 20-nm spacing in each band.

This scalability can be a key factor in ensuring the optimum performance of a network. It can reduce the need for laying new fiber and can maximize the use of existing fiber infrastructure, which helps to ensure high capacity and low latency.

CWDM is often used in metro access networks, as well as in enterprise networks, where a mix of SAN, WAN and voice traffic must be transmitted. It is designed to increase the bandwidth of fiber optic networks with a minimal number of modules.

A CWDM transceiver is composed of an un-cooled CWDM Distributed Feed Back laser, a PIN photodiode integrated with a Trans-impedance Preamplifier (TIA) and a Microprogrammed Control Unit (MCU). The MCU is responsible for monitoring the performance of each channel in the fiber.

Another important part of a CWDM system is a Dual-fiber CWDM Mux Demux, which can be inserted in the Mux port to multiplex or demultiplex signals on two different wavelengths. The Mux Demux can accommodate up to 18 channels for multiplexing and demultiplexing the various kinds of signal, such as data, video, IPTV, HDTV and so on.

CWDM systems are typically standardized using ITU-T G.694.2 standards, which define a grid or wavelength separation of 20 nm in the spectrum from 1270 nm to 1610 and can transport up to 18 CWDM wavelengths over a single fiber. The CWDM grid is transparent to the speed and type of the signal, which allows for a wide range of LAN, WAN and VoIP services to be transported simultaneously over one or two fibers.