CWDM systems

The CWDM and DWDM technologies still remain, to a large extent, uncharted territory for many telecom players. This is due to the fact that these are still relatively new technologies, which, moreover, require considerable theoretical knowledge and practical expertise. However, the harsh market environment and customer expectations inevitably force carriers to introduce these technologies into their networks. There aren’t many partners the carriers can rely on when starting implementing these transmission technologies. Thanks to the highly qualified staff with practical experience in long-haul DWDM transmission and own test and measurement laboratory, Elmat is in a unique position to offer their help. Our offer of services and solutions for CWDM and DWDM networking covers most of the aspects of these technologies, including professional consulting, optical links design, the full portfolio of our own active and passive CWDM and DWDM products (marketed under the Fibrain brand), test and measurement services (measured using best quality instruments) and training courses in optical transmission. To complement the offer, we also have a revolutionary IPoDWDM system based on quasi-transponders from Menara Networks, which delivers the OTN transmission quality at the fraction of its normal cost. This way we can provide the complete package: from consultancy and design to systems and measurements!

The offer is directed in particular at telecom carriers who operate or upgrade CWDM and DWDM networks and who just started investing into these technologies. The products and solutions offered by Elmat find use in all segments of the optical networking market, ranging from metro to regional to core networks so every carrier will come across something of interest. Thanks to the professional and highly qualified staff we are able to select the right technology to match your needs, helping you minimizing the cost of the upgrade and ensuring the desired functionality. Own manufacturing capabilities and cooperation with the world-leading manufacturers allows us to undertake non-standard projects, which often require custom-made solutions with unique characteristics.

At this point, it is worth pointing out that long-haul optical transmission is not a trivial task, the fact which wins more and more recognition amongst the carriers. To accommodate their needs, we offer help with designing optical links, organize training courses in CWDM and DWDM transmission technologies and provide optical testing and measurement services in our laboratory.


Amongst many other products and services, our offer includes:

  • Technology comparison and analysis, to select the right technology to realize a particular project and technical consultancy,
  • Fiber optic link design, to estimate the expected bit error rate BER for the link realized in a particular technology, which includes link viability verification and optimization,
  • Technical design of the passive optics (e.g. multiplexers) and consulting on viability and realizability when unique functionality is required and the off-the-shelf products simply do not cut it,
  • Help with specifying the functional requirements for DWDM networks and preparing the test lists to assess the offerers,
  • Optical tests, measurements and qualification verification of passive and active optical devices,
  • Training courses in CWDM and DWDM technology, of varying level of advancement, with the possibility of tailoring the content to suit the requirements,
  • Manufacturing of CWDM and DWDM devices (marketed under the Fibrain brand), both standard and custom-made,
  • Fibrain active optical modules (SFP, SFP+, XFP, X2, XENPAK) for grey, CWDM and DWDM transmission,
  • XFP modules with built-in OTN processor and FEC coder (Menara Networks quasi-transponders),
  • Multichannel EDFA  amplifiers, Telecom class, in AGC and APC mode.


Experience and competence

Our advantages are highly educated staff, with vast experience in all aspects of the CWDM and DWDM transmission technology and in the OTN technology and also in Metro- and Carrier Ethernet. The combination of practical and theoretical knowledge, manufacturing capabilities and very well equipped test laboratory puts us into a unique position in the telecom market and allows us to fulfill and accommodate the most demanding requirements. To give an example, we were able to help one of the largest Polish carriers in upgrading their core network and increasing its throughput. In this particular case, the challenge was to maintain the existing channels and services and to seamlessly add new CWDM and DWDM channels, along with adding the capabilities for in-service OTDR and power monitoring. The functional requirements, combined with very stringent loss margin meant that we were the only manufacturer capable of meeting the specification.

Optical link design

The correct design of optical DWDM links involves taking into account very many physical phenomena impacting the quality of optical transmission. Amongst them, the OSNR, chromatic and polarization mode dispersion, nonlinear effects (like FWM, SPM or XPM), crosstalk, filter cascades or EDFA gain ripple are typically the most important but not the only. A correctly designed link needs to guarantee good performance after the possible network upgrade and have an adequate bit error rate BER in all conditions. The amount of interacting factors and effects makes the design highly non-trivial. Thanks to our knowledge and experience we are able to offer our assistance in this respect. 



The Optoelectronics and Fiber Optics Laboratory is the R&D department at Elmat Group and specializes in optical measurements and testing of all types of optical components (passive and active) for optical telecommunications. Thanks to our professional staff with large experience in optical metrology and top quality apparatus, we are capable of measuring most of the relevant optical parameters with unrivalled accuracy, spectral and vertical resolution and dynamic range. Our Lab is predominantly equipped with the latest generation measurement instruments from EXFO (with valid calibration certificates) which gives the guarantee of high quality and accurate measurements.

Training courses

The offer is complemented by a range of training courses for carriers. The level of knowledge of CWDM and DWDM transmission engineering even amongst telecom carriers is still insufficient and it’s worthwhile for them to co-operate with companies which do possess this unique know-how. Our courses targeted at carriers include modules on optical link design and optical measurements, and explain the host of various detrimental phenomena impacting the optical transmission and review the current trends in optical networking. The training courses offered by the Fibrain Academy, of varying level of difficulty and advancement, are the optimal means of gaining new and valuable knowledge. 

Passive CWDM and DWDM devices

Passive optics (such as multiplexers and demultiplexers, add/drop filters or dispersion compensators) is the key element of most optical networks. It is of paramount importance to use passive devices of an adequate quality, as the use of low-quality devices will not only shorten the network lifetime, but also reduces its performance and reliability. Fibrain passive devices comply with the most stringent Telcordia recommendations and offer unparalleled optical performance with the best-in-class insertion losses, return loss or isolation. When it comes to non-standard projects, we can assist in specifying and manufacturing the devices and guarantee that the product meets the agreed spec. It is worth noting that often custom made solutions mean significant capital and operational savings! Additionally, we also offer a full range of passive devices for FTTX networks.

OTN quasi-transponders

Most of the current DWDM networks are based on the transponders approach. The dominant trend is to use OTN-compliant transponders, as this technology gives unmatched optical performance. The use of the DWDM transponders, amongst many benefits (e.g. OTN functionality, FEC error correction) involves also significant costs. A solution to this dilemma is to use XFP modules with integrated OTN chip and FEC coder from Menara Networks. This approach allows the carriers to maintain most of the OTN and DWDM benefits (like DWDM tunable optics, FEC coding gain, pre-FEC BER monitoring, PRBS generator and loopbacks, TCMs) at significantly lower cost. Menara Networks quasi-transponders are compatible with any Ethernet switch (supporting both 10G LANPHY and WANPHY), SDH/SONET or IP and MPLS routers, offering the possibility of cost-effectively implementing the true IP over DWDM architecture.

Active optical modules

Fibrain optical modules are offered in all popular formats, including SFP, SFP+, XFP, X2, XENPAK or GBIC and guarantee leading optical performance and quality. We have CWDM and DWDM compatible modules, as well as grey modules, with optical power budgets varying from 24 dB to 40 dB. The modules support all commonly used protocols, including Ethernet, Fibre Channel, SONET/SDH or OTN and supported bitrates vary from 10Mb/s to 10Gb/s. Extended test reports guarantee stringent quality control – if requested each module comes with a spectral test report. Fibrain modules are compatible with switches and routers from all major vendors, including Cisco and HP.

EDFA amplifiers

Indispensable in DWDM networks, EDFA amplifiers allow building long-reach links and lower the costs of long-haul telecommunications. We have in our offer Telecom-class turnkey EDFAs, which boast very good optical parameters such as noise figure (which directly determines the amount of ASE ), low gain ripple (which allows to easily cascade amplifiers) in the full C-band or very low PDG. The amplifiers are available in single stage and double stage (with midstage access for dispersion compensation) configurations and can be used as boosters, line amplifiers or preamplifiers. Both automatic power control APC and automatic gain control AGC modes are supported. The standard versions have 17 dBm or 20 dBm output power rating and gain range 15-25 dB, which is the optimum for most DWDM links with 40 or 80 channels.