标签归档:DWDM Multiplexer

Comparison Between CWDM and DWDM

With the rapid development of telecommunications, the demand for cable capacity is stronger more than ever. WDM (Wavelength Division Multiplexing) will be the preferred method to meet the needs. WDM systems are divided into different wavelength patterns, conventional/coarse (CWDM) and dense (DWDM). This post aims to make a comparison between CWDM and DWDM.

WDM and It’s Working Principle

Wavelength Division Multiplexing 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. A WDM system uses a multiplexer at the transmitter to join the signals together, and a demultiplexer at the receiver to split them apart. With the right type of fiber it is possible to have a device that does both simultaneously, and can function as an optical add-drop multiplexer.

CWDM is the technology of choice for cost efficiently transporting large amounts of data traffic in telecoms or enterprise networks.

DWDM is an optical technology used to increase bandwidth over existing fiber optic backbones.

Comparison between CWDM and DWDM will be illustrated from the following aspects:

  • Channel Numbers: DWDM can fit 40-plus channels into the same frequency range which is twice of CWDM can fit. CWDM is used more often than DWDM due to the cost factor. Now that cabling and transmission has become more affordable, DWDM takes place of CWDM. CWDM is defined by wavelengths, while DWDM is defined in terms of frequencies.
  • Modulated laser: Unlike DWDM deploys cooled distributed-feedback (DFB), CWDM is based on uncooled distributed-feedback (DFB) lasers and wide-band optical filters. These technologies provide several advantages to CWDM systems such as lower power dissipation, smaller size, and less cost. The commercial availability of CWDM systems offering these benefits makes the technology a viable alternative to DWDM systems for many metro and access applications.
  • Transmission Distance: Another major difference between the two is that DWDM is designed for longer haul transmission, by keeping the wavelengths tightly packed. It can transmit more data over a significantly larger run of cable with less interference than a comparable CWDM system. If there is a need to transmit the data over a very long range, the DWDM will likely be the priority in terms of functionality of the data transmittal as well as the lessened interference over the longer distances that the wavelengths must travel. CWDM cannot travel long distances because the wavelengths are not amplified, and therefore CWDM is limited in its functionality over longer distances. Typically, CWDM can travel anywhere up to about 100 miles (160 km), while an amplified dense wavelength system can go much further as the signal strength is boosted periodically throughout the run. As a result of the additional cost required to provide signal amplification, the CWDM solution is best for short runs that do not have mission critical data.

From the comparison above, we can know both the benefits and drawbacks of CWDM and DWDM.  If the transmission distance is short and cost is low, then CWDM may be your first choice. On the contrary, you can consider DWDM. For more information about CWDM and DWMD, you can visit Fiberstore.

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.

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 information data signals, or want to lay out the other cable 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.

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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 module 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.

Save fiber resources CWDM (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 bandwidth CWDM 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.

CWDM system than the price of L band DWDM transceiver 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.

Advanced Optical Components – WDM Multiplexer

WDM Multiplexer is a device that uses Wavelength Division Multiplexing (WDM) technology to combine different optical wavelengths from two or more optical fibers into just one optical fiber. This combining or coupling of the wavelengths can be very useful in increasing the bandwidth of a fiber optic system. WDM multiplexers are used in pairs: one at the beginning of the fiber to couple the inputs and one at the end of the fiber to decouple and then route the separated wavelengths into separate fibers. A WDM multiplexer can be thought of as an optical fiber highway; the highway can support a very large bandwidth, thus increasing the system’s capacity.

Each channel in a WDM multiplexer is designed to transmit a specific optical wavelength. The multiplexer operates very much like a coupler at the beginning of the optical fiber and as a filter at the end of the optical fiber. For example, an 8-channel multiplexer would have the ability to combine eight different channels or wavelengths from separate optical fibers onto one optical fiber. Again, to take advantage of the enormous bandwidth at the end of the optical fiber, another multiplexer (demultiplexer) will recover the separate wavelengths. The figure below shows a simple WDM system composed of multiple light sources, a WDM multiplexer or combiner that combines the wavelengths into one optical fiber, and a WDM demultiplexer or optical splitter that separates the wavelengths to their respective receivers.

Simple WDM System

Types of WDM Multiplexers

  • CWDM & DWDM Multiplexers

WDM multiplexers are available in a variety of sizes, but will most commonly be found with 2, 4, 8, 16, 32, and 64 channels configurations. The types of multiplexers are wideband (or crossband), narrowband, and dense. Wideband or crossband multiplexers (CWDM Multiplexer) are devices that combine a broad range of wavelengths, such as 1310 nm and 1550 nm. A narrowband multiplexer will combine multiple wavelengths with 1000 GHz channel spacing. A dense multiplexer combines wavelengths with 100 GHz channel spacing. Here shows a basic wideband or crossband WDM system.

Basic Wideband or Crossband WDM System

Narrowband WDM (DWDM) systems have channels spaced 1000 GHz, or approximately 8 nm, apart. Here is a figure that shows a basic narrowband WDM system.

Basic Narrowband WDM System

The industry standard on the Dense Wavelength Division Multiplexing Multiplexers (DWDM Multiplexer), as recommended by the International Telecommunications Union (ITU), is 100 GHz or approximately 0.8 nm channel spacing. There are C-band, S-band, and L-band DWDM multiplexers. The C-band is the 1550 nm band which uses wavelengths from 1530 to 1565 nm. The S-band uses wavelengths from 1525 to 1538 nm, and the L-band uses wavelengths from 1570 to 1610 nm.

The closer the channels are spaced together, the higher the number of channels that can be inserted into a band. Currently a spacing of 50 GHz is available (the 50 GHz DWDM multiplexers are generally with 64, 80, 88, 96 channels). It is important to note that as the spacing or the width of each channel decreases, the smaller the spectral width becomes. This is relevant because the wavelength must be stable or sustainable long enough not to drift into an adjacent channel. Besides having a very narrow spectral width, the laser transmitter cannot drift (it must out- put the same wavelength at all times). If the laser transmitter’s output wavelength changes even a few tenths of a nanometer, it could drift into the next channel and cause interference problems.

  • Unidirectional & Bidirectional WDM Multiplexers

There are different configurations of WDM multiplexers. Everything we have covered up to this point describes a unidirectional WDM system. The Unidirectional WDM Multiplexer is configured so that the multiplexer only connects to optical transmitters or receivers. In other words, it allows the light to travel in only one direction and provides only simplex communication over a single optical fiber. Therefore, full-duplex communications require two optical fibers.

A WDM multiplexer that is designed to connect with both transmitters and receivers is called bidirectional (BiDi); in essence, the BiDi WDM Multiplexer is designed for optical transmission in both directions using only one optical fiber. Two channels will support one full-duplex communication link. Here is a figure that shows two BiDi WDM multiplexers communicating over a single optical fiber.

2-Channel BiDi WDM System

Tips for Using WDM Multiplexers

As with any other device that is added to a fiber optic network, there are factors that must be considered. As losses are a factor that must be taken into account, you should remember that the greater the number of channels, the greater the insertion losses when using WDM multiplexers. Other specifications to keep in mind when using WDM multiplexers are isolation, PMD, and the spectral bandwidth.


Summary

WDM multiplexers are widely used devices which provide a way to utilize the enormous bandwidth capacity of optical fiber without the expense of using the fastest laser transmitters and receivers. Just think about it: an 8-channel WDM system using directly modulated 2.5 Gbps laser transmitters carries twice as much data as a single indirectly modulated 10 Gbps laser transmitter. WDM systems allow designers to combine modest performance parts and create an ultra-performance system. WDM systems deliver the most bang for the buck!

Article Source from http://www.fiberopticshare.com/

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)