In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light. This technique enables bidirectional communications over one strand of fiber, as well as multiplication of capacity.

Typical WDM simply used to increase signalling and bandwidth capacity over singlemode fiber optic cable. The result is a link with an aggregate bandwidth that increases with the number of wavelengths employed. In this way WDM technology can maximize the use of the fiber optic infrastructure that is available; what would normally require two or more fiber links instead requires only one. Dense Wave Division Multiplexing (DWDM) combines up to 64 wavelengths onto a single fiber. DWDM technology uses an ITU standard 100GHz or 200GHz spacing between the wavelengths, arranged in several bands at ~1500-1600nm. With DWDM technology, the wavelengths are close together, meaning the transponders are generally more complex and expensive than CWDM(Coarse wavelength division multiplexing). CWDM devices are commonly used in less precision optics and lower cost, un-cooled lasers with lower maintenance requirements.

However, compared with DWDM and Conventional WDM, CWDM is much more cost effective and less power consumption of laser devices. The advantage of CWDM is that it has a much higher density of wavelengths, and also longer distances, especially with MRV's low dispersion solution for the Fiber Driver-LD system.

CWDM Mux/Demux, a type of optical wavelength management device that are based on proven ultra low-loss thin-film filter (TFF) technology, shares the fact that the choice of channel spacing and frequency stability which is the one that EDFA could not use. It features low insertion loss, high channel isolation, wide pass band, low temperature sensitivity and epoxy free optical path. CWDM has gained prevalence in multi-wavelength digital transport architectures because it enables the use of very low cost uncooled distributed feedback (DFB) laser transmitters. Moreover, their powering requirements are reduced and reliability is increased.

One common meaning for CWDM means two (or possibly more) signals multiplexed onto a single fiber, where one signal in the 1550 nm band, and the other in the 1310 nm band. Currently there is an increasing in the channel space. This means the need of less sophisticated and less costly transceivers devices. Operating in the same window of 1550 nm and making use of OH-free silica fibers, maximum efficiencies are achieved in channels 31, 49, 51, 53, 55, 57, 59 and 61 using the wavelengths from 1270 nm through 1610 nm with a channel spacing of 20 nm.

Currently many kinds of related CWDM MUX/DEMUX or DWDM MUX/DEMUX or optical amplifiers are available in the market. Choosing the right one means the correct, integrated devices for error-free high speed data transmission over fiber optic networks. Cost-effective CWDM solution with optimized performance and built in expansion capabilities are available from a host of online network solution companies. Then choosing the most experienced one to get the reliable CWDM solution is very important. As a professinal I suggest you go to Ingellen, a which is a leading manufacture in this field.

Ingellen provides whole series of CWDM products that are tailored for specific applications. For example, 9CH CWDM Mux/Demux, allows you to multiplex/demultiplex eight nine channels into one pair of fiber or two fiber and combined passive 9 channel CWDM Mux and Demux in a single 1U 19'' rack mountable metal box or Standard LGX metal box or Small Plastic ABS box to meet different needs with flexible configuration. CWDM Mux/Demux supplied by Ingellen are based on central wavelengths specified by the ITU-T G.694.2 spectral grid. These TFF devices are offered in standard or extended bandpass versions. They are available as single or multichannel devices.