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Wavelength multiplexing is a good and affordable method of transmitting multiple signals across the same fiber. Each wavelength (color) transports a signal. In this way, you can significantly increase the capacity of existing fiber lines. Combined with Optical Add / Drop Multiplexer (OADM), one can pick and / or add single wavelengths on the way between endpoints. A major advantage of using passive wavelength multiplexing is also that the method is protocol and speed independent.

Wavelength multiplexing is available in 3 versions:

Wavelength Division Multiplexing:

Uses 2 wavelengths - 1310nm and 1550nm.

Coarse Wavelength Division Multiplexing:

Uses 20 wavelengths from 1271nm to 1611nm with 20nm spaces.

Dense Wavelength Division Multiplexing

Uses up to 80 wavelengths from approx. 1528nm to 1561nm with approx. 0.4nm space. Channels are given in frequency from approx. 196thz to 192THz with 50 or 100GHz spaces.


With CWDM the fiber’s wavelength range can be divided into a maximum of  18 channels. CWDM is usually configured over a two-fiber system where a double set of filters and two fibers are used combine, divide and transport the signals each direction.

CWDM technology can also be utilized over one fiber. Every other channel in CWDM is used as Tx and Rx. This utilizes the fact that CWDM SFP transceivers transmit (Tx) at a specific wavelength but receive (Rx) all wavelengths. This way, 9 channels can be utilized with standard CWDM SFPs.


Passive DWDM, Dense Wavelength Division Multiplexing, uses similar technology to CWDM, but now even more channels can be utiliyed on on a single fiber pair. 40 and 80 channel systems over two fibers are common. DWDM can also be used to expand a CWDM channel with 8 or 16 DWDM channels. In this way one can expand infrastructure without building large configurations from the beginning.

Active DWDM uses the same building blocks as passive, but now the possibility of amplifiers and transponders are added. Through our trusted partners, we can offer active DWDM solutions tailored your needs.


Optical Add Drop Multiplexing, or OADM, is a supplement to CWDM. In the configuration example shown, CWDM is configured as a point to point system. With OADM it is possible to remove and/or add wavelengths to the fiber line. In this way, you can build your WDM system by taking out or adding wavelengths at certain locations along the installed fiber.

All FOSS OADM products can be delivered ready for use in the same plug and play solutions as for CWDM; FPM panel (1U/3U), FP Pro panel (1U), DIN box, BUDI wall box and FOSC splicing enclosures.

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