WDM

Wavelength division multiplexing (WDM) is a technology or technique modulating numerous data streams, i.e. optical carrier signals of varying wavelengths (colors) of laser light, onto a single optical fiber. The goal of WDM is to have a signal not to interfere with each other. It is usually used to make data transmission more efficiently. It has also been proven more cost effective in many applications, such as WDM network applications, broadband network application and fiber to the home (FTTH) applications and so on. According to channel spacing between neighbored wavelengths, there are two main types of WDM, including Coarse WDM (CWDM) and Dense WDM (DWDM). Though both of them belong to WDM technology, they are quite different. 

CWDM (coarse wavelength division multiplexing)

CWDM, is a dense wavelength division multiplexing next of kin, the CWDM carrier channel spacing is wider, therefore, light in a single fiber can reuse about 5 to 6 wavelengths, that is where the “dense” and “coarse” appellation come from; Two, CWDM modulation laser using uncooled laser, but DWDM is used in cooling laser. Cooling laser using temperature tuning, uncooled laser adopts electronic tuning. Because the range of temperature distribution is nonuniform in a very wide wavelength, so the temperature tuning is very difficult to realize, the cost is very high. CWDM avoids this problem, so it greatly reduces the cost; the whole CWDM system cost only 30% of DWDM.

CWDM provides a very high access bandwidth with a low cost, suitable for point to point, Ethernet, SONET rings and all kinds of popular network structure, especially suitable for short distance, high bandwidth, access point intensive, communication applications, such as network communication between the building or building. It is particularly worth mentioning is that CWDM with the use of PON (passive optical network).PON is a cheap, one-point to multi-point optical fiber communication mode, in combination with the CWDM, each individual wavelength channel can be used as virtual optical link of PON, Implementation of broadband data transmission between center node and multiple distributed nodes.

There are several companies are offering CWDM related products at present. However, CWDM is a product of cost and performance tradeoffs; inevitably there are some performance limitations. Industry experts point out, at present the CWDM have four following disadvantages: first, CWDM in a single fiber support multiplexing wavelength number is minor, leading to future expansion cost is high; second, multiplexing, multiplexing equipment cost should also be reduced, the device cannot be simply modified of DWDM corresponding equipment; third, CWDM does not apply to metropolitan area network, the distance between metropolitan area network nodes is short , the money that operators use in CWDM equipment expansion can be used to laying more fiber, and get better effect; fourth, CWDM has not yet formed standards.

CWDM Mux/Demux module

CWDM Mux and CWDM Demux are designed to multiplex multiple CWDM channels into one or two fibers. The core of CWDM Module application is the passive MUX DEMUX unit. The common configuration is 1×4, 1×8, 1×16 channels. Available in 19″ Rack Mount or LGX module package. Optional wide band port is available to multiplex with CWDM Channels wavelength.

CWDM is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in DWDM but more than in standard WDM. “Course” means the channel spacing is 20nm with a working channel passband of +/-6.5nm from the wavelengths center. From 1270nm to 1610nm, there are 18 individual wavelengths separated by 20nm spacing.

Cost of Cable

CWDM system carries less data, but the cabling used to run them is less expensive and less complex.

To find out more about flexible, cost-effective distributed CWDM networks, read and get more detail in TOPSTAR to simplifying CWDM connectivity.

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