To top







WDM, Wavelength Division Multiplexing, is the technology that enables multiple parallel signals to be transmitted on one fiber.

With passive filters the light propagates along the fiber in defined wavelength ranges, so called channels. Several wavelengths are combined in the fiber, hence the name wavelength multiplexing. In this way one can significantly increase the capacity of existing fiber installations.

WDM is divided into Coarse WDM and Dense WDM, CWDM and DWDM, which define the spacing in the wavelength range.








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.



We can provide splitters for many different requirements. You will find plug and play solutions ready assembled in panel and modular boxes. For the FOSC and FIST series, we deliver splitters ready assembled in cassettes.

Splitter Function
A passive splitter distributes the optical signal to several fibers without changing the wavelength. The signal may be sent both ways through the splitter (typically for PON) and may in that way also be used for combining signals on to a fiber. To be able to combine the signals, these must have different wavelengths or be sent at different times (TDM - Time Division Multiplexing) so that they do not corrupt each other.