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Wavelength Multiplexing: CWDM and DWDM

CWDM: An optical industry interim standard uses up to eight wavelengths, this scheme is referred to as coarese wavelengtb division multiplexing(CWDM), in accordance with ITU-T(any channel spacing between 8 and 50 nm). ITU-T Recommendation approved in june 2014, extends this down to 1270 nm(18 wavelengths), anticipating the ready commercial availability of fiber with no “water peak” of loss between the 1310-nm and 1550-nm transmission windows, as discussed in Chapter. Such an extended-wavelength planis, of course, applicable only to nonamplified systems until such time as optical amplifiers with similarly extended bandwidths are developed.

DWDM: The International Telecommunications Union(ITU) has defined a usage plan that can scale to as many as 45 wavelengths in the third window and whose spacings have been further split in some systems to yield twice that number. The defined channel designations are for channels spaced 100 GHz apart (about 0.8 nm). Regardless of whether 200-GHz, 100-GHz, or 50-GHz spacings are used, the usage plan is referred to as dense wavelengtb division multiplexing(DWDM). (More about DWDM: DWDM WIKI)

A fwe properties are common to all the plans, each with obvious parallels in RF technology.

♦ The closer the wavelengths are spaced, the harder(and more expensive) it is to separate them in the demultiplexers and simultaneously achieve adequate adjacent channel isolation, minimal in-channel flatness variation, and low insertion loss.

♦ The closer the wavelengths are spaced,the more frequency stabillity is required of the transmitters.

♦ The closer the wavelengths are spaced, the better the signal transmission velocities will match. Four-wave mixing and cross-phase modelation are both maxmum when the signals travel at nearly the same velocity. The degree of matching is, of course, also dependent on fiber dispersionm with standard fiber having high dispersion at 1550 nm but low dispersion at 1310 nm. By contrast, close wavelength spacing leads to reduced crosstalk from stimulated Raman scattering. These mechanisms are discussed later.

♦ The more wavelengths that share a fiber, the lower must be the power per wavelength for a given amount of mutual interaction due to nonlinear glass properties.

As shown in figure shows the relationship of bands, CWDM channels, and DWDM channels. Gable systems using linear DWDM technology generally use 200-GHz-spaced channels from among the set of 20 listed in Table 1, though a few vendors offer 100GHz spacing. For network designs that use fewer than 20 of the listed wavelengths, various vendors have chosen to offer different subsets.


               Relationship of wavelength bands.


           Wavelength Division Multiplexing

Most offer C21 through C35 as the first eight, but noe vendor offers C39 through C53 as the second eight, another offers C45 through C59, and a third has chosen to offer C37 through C51. This is obviously inconvenient for operators who wish to have multiple sources for optical transmitters and DWDM Multiplexer.

Optical divider and connector market strong demand

In many related policies, driven by large-scale light in to the copper retreat has unfolded, with FTTx substantive, ODN products becoming an important part of FTTx
system, may also be the expansion opportunity.

In line with the statistics, the proportion of ODN access equipment investment taken into account 50% ~ 60% of FTTx equipment investment.Could be predicted the years
in the future our country ODN access device how big the marketplace will keep growth trend in excess of 20%, to 2012, how large the marketplace is predicted to attain
14.55 billion yuan.ODN access products are usually made from optical divider, optical connector and also the equipments install these elements (housing, terminal box,
etc.).ODN core technology is mainly manifested within the optical divider, optical connector, passive optical components products.

Bypass the marketplace popular

PLC (planar optical waveguide technology) optical divider is primarily utilized in FTTH user access network, global curiosity about PLC optical divider in ’09 about
3300 wantong, annual rate of development of 32%.Global markets presents different pattern in various area, Japan, Columbia following a curiosity about high-speed
development for quite a while, has become approaching the gentle, demand is pretty stable, makes up about about 50 % from the share of the market;The outcome from the
economic crisis in the usa, influenced by a specific momentum;And developing countries for example China, India, Brazil’s FTTx a fast-growing construction phase, thus
end up being the main growth reason behind the marketplace.

Using the development of our country FTTx, planar optical waveguide technologies have get to be the growth and development of optical communication industry.PLC market
a hot, many are very bullish on passive optical device manufacturers, will be ready to mount the PLC program.Right now, the PLC in the leading manufacturers of optical
communication technology, rich and rich science, and science, etc.

PLC products around the massive in China telecom and China unicom bidding, driven by domestic PLC market, an order income growth is powerful.Through the 12th five-year
plan, operators will accelerate the FTTx network deployment, that will effectively promote the domestic market requirement for passive components, PLC products since
the core device of FTTx, will get a large amount of applications, inside the global share of the market is predicted to assist enhance.

PLC could be the core from the optical divider chip, the chip is essential to produce and manufacture.Recently, we’ve already had some light components enterprises
successfully on PLC chip encapsulation, most foreign enterprises also transfer chips to the country to encapsulate, these conditions to build up PLC optical divider
industry has built favorable conditions.

The connector has huge potential

Requirement of global optical connector in 2008 to 2008, increased by 11% in the year earlier, last year to a single.04 billion.The downstream applications for instance communication, optical network market demand growth, the influence of is anticipated to achieve 1.63 billion by 2012.

Global optical connector within the consumer market, the American companies are the largest.The oldest along with the future development potential may be the Asia Pacific markets.While using advancement of optical fiber cable technology increase the risk for optical fiber gets closer and nearer to the final outcome user, the shorter links, including board interconnection relating to the needs in the growing, thus promoted greatly rise in the quantity of the connector.

This season countries for the policy within the development and integration of optical communication industry will heighten the size the domestic market of optical fiber connector, promote the introduction of domestic optical fiber connector industry.Domestic industry restructuring and three g licensing as well as other factors to market regarding the optical communication network, the resulting including light to the copper back, “FTTx” and so on the most recent market demand, is a big market possibility of optical fiber connector.

Based on China electronics industry association information center, 2009, 280 million optical fiber connector in the domestic market demand, domestic optical fiber connector from 2010 to 2015 how large industry demand will probably be around 12.6% growth, demand will reach 2012, 410 million.As fiber optic broadband network large-scale construction start, therefore, three major telecom operators entry to the building construction is anticipated being orderly development of optical network, optical fiber connector market scale continuously grow.

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