What is Wavelength Division Multiplexing (WDM)? A Beginner's Guide to WDM

Wavelength Division Multiplexing (WDM) has gained tremendous traction in the past few years. It has been the technology of choice for transmitting massive amounts of data in the form of light signals over fiber optic cables. By doing so, it maximizes the capacity of fiber optic networks and avoids excessive cabling. Initially, this classic technology has been used by various private operators and service providers. However, with continuous upgrades and technological improvements, it has been widely adopted by government organizations, private data centers, enterprises, etc. So, what is Wavelength Division Multiplexing (WDM)?

Introduction to Wavelength Division Multiplexing (WDM)

Wavelength division multiplexing (WDM) is a technology that multiplexes individual wavelengths of light to transmit data on a single medium. WDM components work in the opposite manner on the receiving end, by breaking down the combined wavelengths of light back into individual ones and routing them to their receivers. Simply put, a WDM system combines signals through multiplexing (MUX) and separates them using demultiplexing (DEMUX). Wavelength division multiplexing is widely used in telecommunications applications because it allows network capacity to be expanded without laying more fiber.

Advantages of Wavelength Division Multiplexing (WDM)

WDM has various advantages, the following are some of the important ones:

WDM has a large data transmission capacity. The system is capable of transmitting and receiving high-capacity data for high-bandwidth transmission such as 100G and 400G.

WDM easily connects new channels without interrupting existing network traffic, making it flexible and smooth to expand.

Due to the physical properties of light, all wavelengths are independent and do not interfere with each other, thus ensuring the transparency of transmission.

The use of optoelectronic devices such as LED traffic lights, optical fibers, and blue lasers ensures the reliability of the WDM system.

This technology not only maximizes fiber utilization, but also optimizes overall network investment.

Classification of Wavelength Division Multiplexing (WDM)

Based on wavelength, WDM systems are divided into two major categories:

Coarse Wavelength Division Multiplexing (CWDM)

CWDM, or Coarse Wavelength Division Multiplexing, where the term "coarse" refers to the wavelength spacing between channels. The technology utilizes laser signals with wavelengths separated by 20 nanometers (nm). CWDM allows up to 18 channels to be connected via optical fiber with wavelengths ranging as low as 1270 nm. The aggregate capacity of any CWDM cable is 10 Gbps, as each channel is capable of a data rate of 3.25 Gbps. CWDM is widely used in cable television networks, where different signals are used for upstream and downstream signals.

Dense Wavelength Division Multiplexing (DWDM)

DWDM, the abbreviation stands for Dense Wavelength Division Multiplexing. DWDM is defined based on frequency. One of the main advantages of DWDM is that it greatly increases the bandwidth of a single optical fiber. With up to 80 channels transmitting data at 2.5 Gbps, a single optical fiber can transmit 200 billion bits per second. Therefore, it is the first choice for long-distance transmission. DWDM is also used in cloud data centers for logging as a service.

Detailed explanation of the composition of wavelength division multiplexing (WDM)

A WDM system consists of the following four main components:

Transceiver

The transceivers used in WDM systems are lasers of specific wavelengths that convert data signals from IP switches into optical signals to be transmitted over the network. Since each channel is transparent, any type of data, whether voice or video, can be transmitted simultaneously over the optical fiber.

Multiplexers and Demultiplexers

WDM multiplexers and demultiplexers are key elements in optimizing the use of fiber channels. The multiplexer collects all the data and transmits it simultaneously over the network, while the demultiplexer separates the received data into different channels. Traditionally, WDM is two bidirectional channels on a pair of optical fibers. Over time, the technology has evolved significantly, and the total number of channels and the amount of data that can be transmitted have increased.

wiring

Wiring is used to connect two key components - the transceiver and the multiplexer. The LC connector is a commonly used connector that connects the output of the transceiver to the input of the multiplexer.

Dark Fiber Network

Access to dark fiber network is a prerequisite for any WDM system. Employing fiber pairs is considered as one of the common ways to transmit optical traffic. One fiber is used for data transmission and the other for data retrieval.