What is Coarse Wavelength Division Multiplexing (CWDM)?

Coarse Wavelength Division Multiplexing (CWDM) is one of the two main WDM technologies, used to increase bandwidth on optical fiber. This passive technology combines different wavelengths to create separate channels of transmission.

CWDM is generally used for short distances. CWDM signals can only be amplified, so they cannot travel unlimited distances.

What is CWDM?

CWDM is an optical multiplexing technology that combines optical signals of different wavelengths on one strand of fiber. Typically, CWDM can transport up to 18 wavelengths with a channel spacing of 20 nm in the spectrum grid from 1270 nm to 1610 nm. This is a cost-effective solution that works well for short distances and can be used to transmit any combination of voice, data or video traffic.

DWDM stands for dense wavelength division multiplexing and is another WDM technology that uses closely spaced wavelengths to carry more channels on a single fiber. It has a wide range of applications, with many enterprises and telecom service providers relying on it for their networks.

A DWDM system can support more than eight channels of transmission, which is higher than the eight channels available in a CWDM system. Moreover, DWDM systems require less power to operate and have a shorter transmission distance than a CWDM system. Nevertheless, DWDM systems need cooled lasers to maintain their accuracy and performance over long periods of time.

In order to achieve this, a DWDM system uses a cooled laser that adopts temperature tuning and ensures better performance, safety, and longevity of the transceiver. While this increases the cost of a DWDM system, it also results in better performance and accuracy for a longer period of time than an uncooled CWDM system.

When a DWDM transceiver is active, it’s installed in a router cwdm or switch, where it routes the incoming light signal to a transponder that re-converts it into a channelized CWDM or DWDM wavelength. The transponder then connects to the CWDM or DWDM fiber via a jumper.

The CWDM or DWDM wavelength is then transported over the same fiber optic cable to a receiving device, such as an IP-switch. CWDM and DWDM wavelengths can also be transported over a hybrid CWDM and DWDM solution, where DWDM wavelengths are positioned on top of existing channels in the 1530 to 1550 nm band to create up to 28 additional channels. This boosts capacity without new fiber installation or major infrastructure changes.

CWDM Mux/Demux

CWDM Mux/Demux is a device used to increase the capacity of a fiber optic network without adding any additional fibers. It is mainly used in metropolitan area networks and campus networks to meet the higher transmission capacity requirements. There are several different types of CWDM Mux/Demux, which include single-fiber CWDM Mux/Demux, dual-fiber CWDM Mux/Demux, and DWDM Mux/Demux.

A single-fiber CWDM Mux/Demux has a single simplex line port, while a dual-fiber CWDM Mux/Demux includes a duplex line port. However, only one interface of the duplex port is usually in use for connection; the other port is marked with “N/A”.

If you need to expand the transmission capacity of your CWDM Mux/Demux, you can add some special ports that can increase the number of CWDM wavelengths or channels. The most popular ports are the line port and the channel port.

The line port is designed to transmit and receive signals on specific wavelengths, which are also known as WDM wavelengths. Both CWDM and DWDM Mux/Demux support multiple CWDM wavelengths, which can be up to 18 channels in CWDM systems and up to 40 channels in DWDM systems.

You can also add a monitor port on the CWDM Mux/Demux to better manage the link. This port will allow you to check the dB level of the signal without interrupting service. It can also help you track the status of the entire CWDM link.

In addition to the standard CWDM channel port, some DWDM Mux/Demux also have special port for 1310nm and 1550nm, which are the two most common WDM wavelengths for long distance transmission. These ports are useful when you want to add 1310nm or 1550nm wavelengths into existing DWDM networks.

As a result, you can create a multi-wavelength DWDM system by connecting different DWDM Mux/Demux to the same CWDM SFP transceiver. This way, you can extend the transmission distance of your DWDM network without any extra fibers or expensive upgrades.

DWDM Mux/Demux are the preferred option for long-haul transmission. They deliver the benefits of DWDM technology in a fully passive solution, which requires no power supply or cooling to operate. Moreover, they are very robust and have a lifetime of 100+ years.

CWDM Channel Plan

Coarse Wavelength Division Multiplexing (CWDM) is a common method for doubling the bandwidth capacity of single fiber cables. CWDM works by using two channels – one sending, the other receiving data – over a single strand of fiber. The channels are spaced 20nm apart and are defined by ITU standards, allowing for up to 18 wavelengths to be transported simultaneously.

CWDM systems are typically installed in metro networks, which require high speed connectivity and low cost. However, for applications requiring long distance transmissions, dense wavelength division multiplexing (DWDM) is more suitable. DWDM uses erbium doped fiber amplifiers, which boost signals to increase their amplitude over long distances. This allows DWDM to operate over longer distances than CWDM, but it also requires additional equipment, such as amplifiers and signal regenerators.

The main difference between CWDM and DWDM is that the wavelengths used in a CWDM system are distributed across a wide spectrum of light, whereas in a DWDM system the wavelengths are tightly packed together. This allows the signals to be amplified and travel over much longer distances, which is crucial for the long haul transmission of high-speed data.

This increases the bandwidth of each channel and therefore the transmission speed of the network. This increased speed makes CWDM an excellent choice for connecting to high-speed WANs, LANs and enterprise networks.

A CWDM system consists of a set of optical transmitters and receivers which are connected over a single fiber cable. The transmitters send data to the receivers on either side of the cable, which are connected together via a CWDM Mux/Demux at each end.

FS offers a full range of CWDM transceivers, including CWDM SFPs and CWDM SFP+ modules that are compatible with a variety of wavelengths and speeds. CWDM SFPs allow up to 18 wavelengths to be carried simultaneously on one fiber, while a CWDM SFP+ module can carry up to 40 channels at the same time.

CWDM is a less expensive alternative to DWDM, although it cannot be used in long-haul applications and may not provide the highest data rates over long distances. It also has a limited reach, and it is not suitable for high-speed protocols that require 100Gbps per channel.

CWDM Application

CWDM is a standardized solution for transporting multiple WAN (wide area network) and LAN (local area network) channels over one or more fiber pairs. It is also a good choice cwdm for SAN (storage area network) applications, as it enables data to be transported over a single fiber without interfering with another fiber.

Compared to DWDM, which has a wider wavelength spacing and requires expensive amplifiers to boost the signal, CWDM is a more cost-effective option. It also has a lower number of active wavelengths per fiber, which allows it to be used in shorter distance applications.

It can use an uncooled laser and a simple thin-film filter to transmit wavelengths, thereby reducing the size of the optical components. Additionally, it is less prone to alignment issues and enables the development of smaller-package devices that consume less power.

In addition, CWDM can scale up to a total of eight wavelengths within the 1270-1610-nm spectrum, using wavelength-division-multiplexing. This allows it to transport up to 18 CWDM wavelengths over a pair of fibers, which is a good solution for many short runs.

However, it is important to note that CWDM cannot transmit signals over long distances, as it lacks the ability to amplify light. This makes it ineffective for long-haul applications that require transmission over tens of kilometers, as it can only travel up to 100 miles.

To overcome this limitation, CWDM uses inline regenerators that fully reamplify, reshape, and retime an outgoing signal. They are especially useful in ensuring that dispersion is minimized, which helps to ensure reliable transmission over long distances.

Another way to help CWDM scale is to add a wavelength-division-multiplexing system, such as DWDM, which allows signals to be amplified across the entire spectrum. This can be useful for enhancing data capacity over an existing network by increasing the number of wavelengths available.

CWDM can also be deployed in a ring, mesh, or point-to-point configuration, which can be useful for interconnecting geographically dispersed LANs and SANs. CWDM rings can also offer self-healing protection, such as link breaking and node failure separation.

CWDM is a cost-effective option for connecting geographically dispersed networks, and it has the potential to be highly scalable. It is also suitable for high-bandwidth networks, such as 5G, where large capacity is required to meet the data needs of consumers.