RP Photonics logo
RP Photonics
Technical consulting services on lasers, nonlinear optics, fiber optics etc.
Profit from the knowledge and experience of a top expert!
Powerful simulation and design software.
Make computer models in order to get a comprehensive understanding of your devices!
Success comes from understanding – be it in science or in industrial development.
The famous Encyclopedia of Laser Physics and Technology – available online for free!
The ideal place for finding suppliers for many photonics products.
Advertisers: Make sure to have your products displayed here!
… combined with a great Buyer's Guide!
VLib part of the

Wavelength Division Multiplexing

<<<  |  >>>  |  Feedback

Buyer's Guide

The ideal place to find suppliers for photonics products: high-quality information, simple and fast, and respects your privacy!

36 suppliers for equipment for wavelength division multiplexing are listed.

You are not yet listed? Get your entry!

Ask RP Photonics for advice concerning the physical principles or various technical details of wavelength division multiplexing.

Acronym: WDM

Definition: a multiplexing technique working in the wavelength domain

German: Wellenlängen-Multiplexing

Categories: lightwave communications, methods

How to cite the article; suggest additional literature

Wavelength division multiplexing is a kind of frequency division multiplexing – a technique where optical signals with different wavelengths are combined, transmitted together, and separated again. It is mostly used for optical fiber communications to transmit data in several (or even many) channels with slightly different wavelengths. In this way, the transmission capacities of fiber-optic links can be increased strongly, so that most efficient use is made not only of the fibers themselves but also of the active components such as fiber amplifiers. Apart from telecom, wavelength division multiplexing is also used for, e.g., interrogating multiple fiber-optic sensors within a single fiber.

WDM in Telecom Systems

Theoretically, the full data transmission capacity of a fiber could be exploited with a single data channel of very high data rate, corresponding to a very large channel bandwidth. However, given the enormous available bandwidth (tens of terahertz) of the low-loss transmission window of silica single-mode fibers, this would lead to a data rate which is far higher than what can be handled by optoelectronic senders and receivers. Also, various types of dispersion in the transmission fiber would have very detrimental effects on such wide-bandwidth channels, so that the transmission distance would be strongly restricted. Wavelength division multiplexing solves these problems by keeping the transmission rates of each channel at reasonably low levels (e.g. 10 Gbit/s or 100 Gbit/s) and achieving a high total data rate by combining several or many channels.

Two different versions of WDM, defined by standards of the International Telecommunication Union (ITU), are distinguished:

Due to the wide amplification bandwidth of erbium-doped fiber amplifiers, all channels can often be amplified in a single device (except in cases where e.g. the full range of CWDM wavelengths is used). However, problems can arise from the variation of gain with wavelength or from interaction of the data channels (crosstalk, channel interference) e.g. via fiber nonlinearities. Enormous progress has been achieved with a combination of various techniques, such as the development of very broadband (double-band) fiber amplifiers, gain flattening filters, nonlinear data regeneration and the like. The system parameters such as channel bandwidth, channel spacing, transmitted power levels, fiber and amplifier types, modulation formats, dispersion compensation schemes, etc., need to be well balanced to achieve optimum overall performance.

Even for existing fiber links with only one or a few channels per fiber, it can make sense to replace senders and receivers for operation with more channels, as this can be cheaper than replacing the whole system with a system with a higher transmission capacity. In fact, this approach often eliminates the need to install additional fibers, even though the demand on transmission capacities is increasing enormously.

Apart from increasing the transmission capacity, wavelength division multiplexing also adds flexibility to complex communication systems. In particular, different data channels can be injected at different locations in a system, and other channels can be extracted. For such operations, add–drop multiplexers can be used, which allow one to add or drop data channels based on their wavelengths. Reconfigurable add–drop multiplexers make it possible to reconfigure the system flexibly so as to provide data connections between a large number of different stations.

In many cases, time division multiplexing (TDM) can be an alternative to wavelength division multiplexing. Here, different channels are distinguished by arrival time rather than by wavelength.


[1]H. Ishio et al., “Review and status of wavelength-division-multiplexing technology and its application”, J. Lightwave Technol. 2 (4), 448 (1984)
[2]A. E. Willner and S.-M. Hwang, “Transmission of many WDM channels through a cascade of EDFA's in long-distance links and ring networks”, J. Lightwave Technol. 13 (5), 802 (1995)
[3]N. S. Bergano and C. R. Davidson, “Wavelength division multiplexing in long-haul transmission systems”, J. Lightwave Technol. 14 (6), 1299 (1996)
[4]G. E. Keiser, “A review of WDM technology and applications”, Opt. Fiber Technol. 5 (1), 3 (1999)
[5]L. F. Mollenauer et al., “Demonstration of massive wavelength-division multiplexing over transoceanic distances by use of dispersion-managed solitons”, Opt. Lett. 25 (10), 704 (2000)
[6]ITU Standard G.694.1 (06/02), “Spectral grids for WDM applications: DWDM frequency grid”, International Telecommunication Union (2002)
[7]ITU Standard G.694.2 (12/03), “Spectral grids for WDM applications: CWDM wavelength grid”, International Telecommunication Union (2003)

(Suggest additional literature!)

See also: fibers, optical fiber communications, time division multiplexing
and other articles in the categories lightwave communications, methods

In the RP Photonics Buyer's Guide, 53 suppliers for equipment for wavelength division multiplexing are listed.

How do you rate this article?

Click here to send us your feedback!

Your general impression: don't know poor satisfactory good excellent
Technical quality: don't know poor satisfactory good excellent
Usefulness: don't know poor satisfactory good excellent
Readability: don't know poor satisfactory good excellent

Found any errors? Suggestions for improvements? Do you know a better web page on this topic?

Spam protection: (enter the value of 5 + 8 in this field!)

If you want a response, you may leave your e-mail address in the comments field, or directly send an e-mail.

If you like our website, you may also want to get our newsletters!

If you like this article, share it with your friends and colleagues, e.g. via social media:


Evaluation of Technologies

In the laser and photonics industry, it is often essential to obtain competent evaluations of certain technologies:

Get help!

Involving a top expert such as Dr. Paschotta into technology evaluations can have many advantages:

Just contact RP Photonics to find out what we can do for you!

– Show all banners –

– Get your own banner! –