Tag Archives: DWDM multiplexer

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.

1

             Relationship of wavelength bands.

 

           Wavelength Division Multiplexing
2

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.

CWDM in optical fiber transmission network of comprehensive solutions

FOREWORD

1. The background of the project:Radio and television networks in recent business growth is faster in a given area, is the region development education network access project, due to the previous optical fiber network resources is mainly used in cable television network, optical fiber resources is not so rich, many county to the town had no residual fiber resources, to increase the data business, now want to be in the original on the fiber optic cable TV network transmission using again, plus infomation data signals, or want to lay out the other cable?Is the main work, need to solve as many towns in this area belongs to mountainous area, cable laying is not very convenient, considering various factors such as resources, cost, on the radio and television networks company specialized in optical network access technology co., LTD. Shenzhen Fiberstore CWDM system to conduct a comprehensive performance analysis and product testing.And start in areas such as education network access to A project on each node USES many Fiberstore CWDM system equipment.

2. Network topology

The radio and television networks of CWDM project at present is mainly used to implement the education network (10/100 MBPS Ethernet) hybrid transmission signals and the cable television network, the current direction of projects with a total of eight different contact, sharing the 3 sets of Fiberstore the CWDM system equipment.
In this scenario, A computer room – B node transfer 2 10/100 MBPS data signals and A cable TV signal, which is based on WDM CWDM access, two 10/100 MBPS signals after Fiberstore C5002S through Fiberstore HA – WDM multiplexer, and cable television signals and reuse all the way to A single fiber, transfer to the access point B region, middle transmission distance of 50 km, implements and Ethernet cable TV signal on the single fiber CWDM solution of hybrid transmission.
A room – C nodes use sea pegatron C5002S system combined with high speed and CWDM terminal transceiver effectively cooperate with access, realize two-way 10/100 MBPS of hybrid transmission over A single optical fiber.
A-D-E by Fiberstore C5004S system combining various nodes of high speed and the corresponding CWDM transceiver implementation 4 10/100 MBPS signals on A single optical fiber access project, through the high speed connection between each contact, through the terminal CWDM wavelengths optical transceiver connected to A contact switch, after the C5004S system in the computer room 4 different signals, respectively in different wavelengths transmitted to each destination, after D primary school, through high speed download local signal, the remaining 3 to continue down the road signal to the corresponding destination.

CWDM access scheme

1.Save fiber resourcesCWDM (Coarse where division multiplexing) Coarse wavelength division multiplexing system, which USES optical multiplexer in the different optical fiber transmission wavelength multiplexing in a single fiber transmission;On the receiving end of A link, using wavelength multiplexer and then revert to the original wavelength, using optical fiber all the way, on the whole link is solved effectively under the condition of the optical fiber resources extremely nervous network access, this scenario, A, D, E, between transmission on A single fiber and four 10/100 MBPS (also can be 1000 MBPS) signal, A room – B node is in the original cable TV signal transmission on A single fiber loading 2 10/100 MBPS signals, save A lot of fiber resources. 2.More business and high bandwidthCWDM is a according to the practical application to the transfer rate of adaptation based transmission platform, support a variety of business transfer.At each wavelength, the support of the business including 10 m / 100 m / 1000 m Ethernet, 155 m / 622 m / 2.5 G of SDH, 155 m / 622 m ATM business, as well as the Fiber Channel business, and so on.The whole system capacity to play a few Gbps data signal.Fully meet user bandwidth requirements in quite some time.This scenario USES is 10/100 MBPS business with cable TV signal for hybrid transmission.

3.Cost-effective, to facilitate the network upgrades

CWDM system than the price of DWDM Multiplexer is relatively low, due to the power of CWDM is small, small volume, easy to use, thus supporting facilities, personnel training and the late maintenance cost is low.Compared with optical cable project: using CWDM device is opened rapidly, low cost, convenient network upgrades, late and increasing need of signal directly, or replace the higher rate of product, don’t need to change the fiber link, convenient network upgrades, reduces the network upgrade costs.The above scenario A-D-E, if change into 1000 MBPS data signals, the capacity of the network directly to upgrade to the 4 GBPS.

CWDM in hybrid access network in the use of the business

With the improvement of people’s living standard, nowadays a single network access gradually cannot satisfy people’s demand for network now, CWDM system support for the characteristics of business more and more get the attention of people, can also provide E, FE, GE, STM 1/4/16 SDH and ATM signaling, CATV video interface and other businesses such as access CWDM system solutions, to meet the requirements of people now.

(Read more:DWDM OADM,CWDM Multiplexer,DWDM MUX DEMUX)