A Brief Overview to Dense Wavelength Division Multiplexing (DWDM)

In fiber optic communications, WDM (wavelength-division multiplexing) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i.e., colors) of laser light. This technique enables bidirectional communications over one strand of fiber as well as multiplication of capacity. Generally, WDM could be divided into CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). Below part will give a brief introduction to DWDM.


Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. Using DWDM, up to 80 separate wavelengths or channels of data can be multiplexed into a light stream and transmitted on a single optical fiber. This process allows for multiple video, audio, and data channels to be transmitted over one fiber while maintaining system performance and enhancing transport systems. This technology responds to the growing need for efficient and capable data transmission by working with different formats, such as SONET/SDH, while increasing bandwidth.


The fiber optic amplifier in DWDM system provides a cost efficient method of taking in and amplifying optical signals without converting them into electrical signals. In addition, DWDM amplifies a broad range of wavelengths in the 1550nm region. For example, with a DWDM system multiplexing 16 wavelengths on a single optical fiber, carriers can decrease the number of amplifiers by a factor of 16 at each regenerator site. Using fewer regenerators in long-distance networks results in fewer interruptions and enhanced efficiency.


A basic Dense Wavelength Division Multiplexing contains five main components:

1. DWDM Terminal Multiplexer: This device contains one wavelength converting transponder for each wavelength carried. It receives an input optical signal, converts it to an electrical signal and then retransmits it as an optical signal (a process abbreviated as O/E/O) using a 1550nm laser beam. The MUX (multiplexer) takes a number of 1550nm optical signals and places them on a single optical fiber. This terminal multiplexer may also contain an EDFA (Erbium Doped Fiber Amplifier) to amplify the optical signal.

2. Intermediate Line Repeater: These are amplifiers placed every 80 to 100 kilometers to compensate for loss of optical power; amplification is done by an EDFA, usually consisting of several amplifier stages.

3. Intermediate Optical Terminal, or Optical Add/Drop Multiplexer: This is a remote site amplifier placed where the signal may have traveled up to 140 kilometers; diagnostics and telemetry signals are extracted or inserted.

4. DWDM Terminal Demultiplexer: This device breaks the multi-wave signal back into individual signals; these may be sent to O/E/O output transponders before being relayed to their intended destinations, i.e. client-layer systems.

5. Optical Supervisory Channel (OSC): This channel carries information about the multi-wave optical signal and may provide data about conditions at the site of the intermediate line repeater.


DWDM has several key advantages:

  • Transparency—Because DWDM is a physical layer architecture, it can transparently support both TDM (Time Division Multiplex) and data formats such as asynchronous transfer mode (ATM), Gigabit Ethernet, Enterprise System Connection (ESCON), and Fibre Channel with open interfaces over a common physical layer.
  • Scalability—DWDM can leverage the abundance of dark fiber in many metropolitan area and enterprise networks to quickly meet demand for capacity on point-to-point links and on spans of existing SONET/SDH rings.
  • Dynamic provisioning—Fast, simple, and dynamic provisioning of network connections give providers the ability to provide high-bandwidth services in days rather than months.
  • Robust and reliable—Well-engineered DWDM systems offer component reliability, system availability and system margin.

To sum up, DWDM system is very important in optical communication. If you are still confused about it, feel free to consult customer service at FS.COM. We are willing to solve your puzzles and offer the right solution for you. FS.COM provides various kinds of WDM products, such as 10GBASE DWDM, 40 channel DWDM Mux, CWDM Mux/Demux module and so on. It is an excellent option for choosing CWDM and DWDM equipment.