What is DWDM in networking?
Dense wavelength-division multiplexing (DWDM) is an optical fiber multiplexing technology that increases the bandwidth of fiber networks. DWDM combines data signals from sources over a single pair of optical fibers and it maintains separation of the data streams. A separate light wavelength carries each signal. The IETF states that: “A network slice is programmable and has the ability to expose its capabilities”. DWDM systems can support up to 80 channels or more, each with a different wavelength of light, which can then be used to transmit data, voice, and video signals over long distances without the need for regenerating or amplifying the signals. This makes DWDM an ideal solution for high-speed data communication over long distances, such as in telecommunications and internet service providers.
DWDM Basics
How does Dense Wavelength-Division Multiplexing (DWDM) work?
DWDM works by using lasers to generate light signals of different wavelengths, which are then combined and sent over a single fiber. The receiver at the other end of the fiber separates the different wavelengths using a demultiplexer, allowing the original signals to be retrieved. DWDM systems can also use amplifiers to boost the strength of the signals, allowing them to be transmitted over even longer distances without losing clarity or quality. Coarse Wavelength Division Multiplexing (CWDM) is another viable options when trying to solve customers' growing bandwidth needs.
What are the Components of a DWDM Optical System?
Several components work together to make up a DWDM optical system. Below is a high-level overview of each component and its function:
- Router – sends the original data stream to the transponder.
- Transponder – maps the data stream to an outgoing light wavelength that suits the DWDM application.
- Muxponder – maps several data streams to an outgoing light wavelength that suits the DWDM application.
- Optical add/drop multiplexers (OADM) – consolidates multiple wavelengths of light onto an optical fiber
- Optical amplifiers – boosts the signal through the fiber optic network.
- Fiber optic cables – data travels across the fiber optic network as wavelengths of light.
- Receiving equipment – the signal arrives at its destination, goes through another OADM to de-multiplex it into different wavelengths, and moves through the transponder (or muxponder) and router to the receiving equipment (e.g. a television, computer, etc.)
Passive DWDM vs Active DWDM
DWDM is divided into two primary types: active DWDM and passive DWDM. Active DWDM is a DWDM system where the wavelengths transmitted through optical fiber are actively managed and manipulated. In active DWDM Systems Transponders, amplifiers and other "active" components are designed to compensate for signal attenuation and distorting, enabling DWDM system to support longer distance transmissions. This makes active DWDM systems ideal for long haul DWDM. Passive DWDM has no active components (such as signal amplifiers) to transmit data, making the transmission distance limited to the optical modules. Passive DWDM is suited for metro DWDM and other short distance middle mile data transmission.
Metro DWDM vs Long Haul DWDM
Metro DWDM systems are used for transmitting data across moderate distances of a few hundred miles to cover a large metropolitan area. Whereas, long haul DWDM sends data across greater distances, often spanning hundreds or even thousands of miles. However, as providers strive to become more and more competitive (both locally and globally), many are beginning to implement both metro and long haul DWDM using both capacity-reach and power-cost optimized optical transport.
What is CWDM?
Coarse Wavelength Division Multiplexing (CWDM) is a simpler and cost effective technology that uses fewer wavelengths of light to transmit data over shorter distances. CWDM is suitable for applications where the distance between the endpoints is less than 80 km, and the data transmission rates are lower, typically less than 10 Gbps. Looking to learn more? Take a deep dive with our CWDM vs DWDM blog or download the IP over DWDM Whitepaper.
