Wavelength division multiplexing or WDM has gained immense traction over the last few years. It has been the preferred choice of technology for transporting massive data in the form of light signals over a fiber cable. By doing so, it maximizes fiber network capacity and avoids excess wiring. Initially, this classic technology has been used by various private carriers and service providers.
However, with consistent upgrades and unmatched technical improvements, it has been widely adopted by governmental organizations, privately owned data centers, corporate empires, and many more. Are you intrigued to know more about WDM technology? This post attempts to answer every question you might have regarding wavelength division multiplexing. Read on to know more.
What is Wavelength Division Multiplexing?
WDM is a technique that multiplexes individual light wavelengths for transmitting data over a single medium. WDM components work opposite at the receiving end by de-muxing the combined light wavelength back into an individual and routed to their receivers. Simply, the WDM system combines signals with multiplexing (MUX) and separates them using de-multiplexing (DEMUX). Wavelength division multiplexing is popularly used in telecommunication applications as it expands the network capacity without laying more fiber.
Advantages of WDM
WDM offers various advantages, and the following are a few important ones:
- WDM has an ultra-large data transmission capacity. The system is capable of transmitting and receiving high-capacity data used for high-bandwidth transmissions like 100G, 400G, and more.
- WDM easily connects new channels without disrupting the existing network traffic, making it flexible for a smooth expansion.
- Owing to the physical properties of light, all wavelengths are independent and do not interfere with each other, and hence ensure transmission transparency.
- Adopting optoelectronics devices such as LED traffic lights, optical fiber, blue laser, and so on guarantees the reliability of the WDM system.
- The technology not only maximizes fiber utilization but optimizes overall network investments.
Understanding the Classification of WDM in Detail
Depending upon the wavelength, the WDM systems are divided into two main categories:
CWDM:
The acronym stands for coarse wavelength division multiplexing, wherein the term coarse is referred to as the wavelength spacing between channels. This technology utilizes laser signals at wavelengths spaced 20 nanometers (nm) apart. CWDM allows up to 18 channels to be connected over fiber optics with a wavelength ranging down to 1270 nm. The aggregate ability for any CWDM cable is 10 Gbps as every channel is capable of data rates of 3.25 Gbps. CWDM is popularly being used in cable television networks, in which different signals are used for upstream and downstream signals.
DWDM:
The abbreviation stands for dense wavelength division multiplexing. DWDM is defined in terms of frequencies. One of the major advantages of DWDM is that it intensely increases the bandwidth of a single fiber cable. With up to 80 channels carrying data at 2.5 Gbps, a single fiber cable can carry 200 billion bits per second. Therefore, it is the preferred choice for long-haul transmissions. DWDM is also used in cloud data centers for their logging as a service.
A Detailed Discussion on Components of WDM
The WDM system consists of four main components as described below:
Transceivers:
- Transceivers used in a WDM system are wavelength-specific lasers that coverts data signals from IP switches to optical signals to be transmitted over the network. Since each channel is transparent, any type of data – be it voice or video– can be transported simultaneously over a fiber.
MUX and DEMUX:
- WDM multiplexers and de-multiplexers are key requisites for optimizing the use of fiber channels. Multiplexers gather all the data and transmit it simultaneously over a network, while de-multiplexers separate the received data into different channels. Traditionally, WDM were two bi-directional channels over a pair of fibers. The technology has significantly evolved with time and both the total number of channels and amount of data that can be transported has increased.
Patch Cable:
- A patch cable is used to join the two key elements - transceiver and multiplexer. LC connector is one popular connector that connects the output of the transceivers to the multiplexer input.
Dark Fiber Network:
- Accessing a dark fiber network is a prerequisite for any WDM system. The adoption of fiber pairs is considered one of the common ways of transporting optical traffic. One fiber is used for data transmission, while the other is used for data retrieval.
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Difference between WDM and DWDM
WDM (Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) are both technologies used in optical communication to increase data transmission capacity by simultaneously transmitting multiple signals on different wavelengths of light. Here are the key differences between WDM and DWDM:
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Wavelength Spacing:
In WDM, the spacing between wavelengths (channels) is relatively wider, typically in the range of several nanometers.
Whereas DWDM uses much narrower wavelength spacing, usually on the order of a few GHz or even less, allowing for a significantly higher number of channels to be packed within the same optical fiber.
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Number of Channels:
WDM systems typically support a limited number of channels, often up to 16 or 32 wavelengths.
Whereas DWDM can support a much larger number of channels, ranging from 40 to over 80 wavelengths, making it ideal for high-capacity networks.
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Channel Capacity:
Each wavelength channel in WDM can carry data at lower data rates, usually up to 10 Gbps (Gigabits per second).
Whereas DWDM channels can handle much higher data rates, ranging from 10 Gbps to 100 Gbps or even 400 Gbps, depending on the technology used.
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Optical Amplification:
WDM systems require individual amplification for each wavelength channel, which can increase complexity and cost.
Whereas DWDM benefits from the use of erbium-doped fiber amplifiers (EDFAs) that amplify multiple wavelengths simultaneously, simplifying the network architecture and reducing amplification costs.
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Network Reach:
WDM is commonly used for short to medium-distance optical networks, such as metro and campus networks.
Whereas DWDM is widely deployed in long-haul and ultra-long-haul optical networks, covering inter-city and transcontinental distances.
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Cost and Complexity:
WDM systems are generally more cost-effective and less complex than DWDM systems due to their simpler architecture.
While DWDM technology involves higher costs and increased complexity, primarily due to the need for precise wavelength management and advanced optical amplification.
WDM is suitable for scenarios requiring moderate capacity and shorter distances, while DWDM is the preferred choice for high-capacity, long-haul networks that demand a large number of channels with high data rates.
