An Overview of WDM

WDM stands for Wavelength Division Multiplexing. WDM is the most important and most popular method to increase the capacity of a single strand of fiber.  

Traditionally, only one colored light was used on a single strand of fiber to carry the information, such as 1550nm light. However, starting from the early 1990s, the Internet boom pushed service providers to find a method to increase the capacity on their network in the most economical way. That is when WDM devices were invented.

In a WDM system, many different colored lights are combined by a WDM multiplexing device and put into a single strand of fiber, each color is called a channel.

On the receiver side, each color is separated into its own channel by a WDM de-multiplexing device. It shows that a single fiber’s capacity is increased by 40 times with a 40 channel WDM. The beauty of WDM is that you only need to upgrade the end equipment, no need to dig up trenches to bury more fibers, which is much more costly.   

Communication systems are designed differently, and the width of the gap between each wavelength varies. Depending on channel spacing, WDM can be subdivided into CWDM and DWDM.

CWDM and DWDM

CWDM supports up to 18 wavelength channels transmitted through a fiber at the same time. To achieve this, the different wavelengths of each channel are 20nm apart.

DWDM, supports up to 80 simultaneous wavelength channels, with each of the channels only 0.8nm apart. 

CWDM technology offers a convenient and cost-efficient solution for shorter distances of up to 70 kilometers.

For distances between 40 and 70 kilometers, CWDM tends to be limited to supporting eight channels. Unlike CWDM, DWDM connections can be amplified and can, therefore, be used for transmitting data much longer distances.

 

• Wavelengths Used in WDM

 

DWDM is typically limited to 1450 to 1650nm

CWDM may operate over the full range of 1280 to 1650nm

 

• Laser Source Spacing

 

DWDM uses lasers at ~0.8nm spacing

CWDM uses lasers at a 20nm spacing  

Advantages of WDM Technology

1. Large transmission capacity can save valuable optical fiber resources. For single-wavelength optical fiber systems, a pair of optical fibers are needed to transmit and receive a signal, while for WDM systems, no matter how many signals there are, the entire multiplexing system only needs a pair of optical fibers. For example, for 16 2.5gb /s systems, the single-wavelength optical fiber system needs 32 optical fibers, while the WDM system only needs 2 optical fibers.
2. It can transmit different types of signals such as digital signals, analog signals, etc., and can synthesize and decompose them.
3. When the network capacity is expanded, there is no need to deploy more optical fiber, nor need to use high-speed network components, only need to change the end machine and add an additional wavelength of light to introduce any new service or expansion capacity, so WDM technology is an ideal means of capacity expansion.
4. The dynamic reconfigurable optical network can be constructed, and the all-optical network with high flexibility, high reliability, and high survivability can be formed by using optical division multiplexer (OADM) or optical cross-connection device (OXC) at the network nodes.

WDM Technology Is Expected to Optimize Cost for 5G Development

The 5G wireless infrastructure necessitates wavelength division multiplexing (WDM) technology to optimize fiber usage. Fixed and reconfigurable multiplexing are two approaches that provide tradeoffs in terms of network scalability, reliability, and cost. Optical networks closest to the antenna are the most cost sensitive and can benefit from fixed WDM solutions. Gigalight’s broad portfolio of WDM modules is available in various configurations including coarse-WDM (CWDM), dense-WDM (DWDM) modules and other WDM solutions.