Comparison Between CWDM & DWDM Technology

For a better signal transmission in fiber-optic communication, different kinds of technologies are applied to the industry. Wavelength-division multiplexing (WDM) is one of the commonly used technologies which multiplexes a number of optical carrier signals onto a single optic fiber by using different wavelengths of laser light. That is to say, WDM enables two or more than two wavelength signals to transmit through different optical channels in the same optical fiber at the same time.

WDM

In the WDM system, there are two types of divisions – CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). They are both using multiple wavelengths of laser light for signal transmission on a single fiber. However, from the aspects of channel spacing, transmission reach, modulation laser and cost, CWDM and DWDM still have a lot of differences. This article will focus on these distinctions and hope you can have a general understanding about CWDM and DWDM technology.

Channel Spacing

As their names suggest, the words “coarse” and “dense” reveal the difference in channel spacing. CWDM has a wider spacing than DWDM. It is able to transport up to 16 wavelengths with a channel spacing of 20 nm in the spectrum grid from 1270 nm to 1610 nm. But DWDM can carry 40, 80 or up to 160 wavelengths with a narrower spacing of 0.8 nm, 0.4 nm or 0.2 nm from the wavelengths of 1525 nm to 1565 nm (C band) or 1570 nm to 1610 nm (L band). It is no doubt that DWDM has a higher performance for transmitting a greater number of multiple wavelengths on a single fiber.

CWDM-VS-DWDM

Transmission Reach

Since the wavelengths are highly integrated in the fiber during light transmission, DWDM is able to reach a longer distance than CWDM. The amplified wavelengths provide DWDM with the ability of suffering less interference over long-haul cables. Unlike DWDM system, CWDM is unable to travel unlimited distance. The maximum reach of CWDM is about 160 kilometers but an amplified DWDM system can go much further as the signal strength is boosted periodically throughout the run.

Modulation Laser

CWDM system uses the uncooled laser while DWDM system uses the cooling laser. Laser cooling refers to a number of techniques in which atomic and molecular samples are cooled down to near absolute zero through the interaction with one or more laser fields. Cooling laser adopts temperature tuning which ensures better performance, higher safety and longer life span of DWDM system. But it also consumes more power than the electronic tuning uncooled laser used by CWDM system.

Cost

Because the range of temperature distribution is nonuniform in a very wide wavelength, so the temperature tuning is very difficult to realize, thus using the cooling laser technique increases the cost of DWDM system. Typically, DWDM equipment is four or five times more expensive than CWDM equipment.

Conclusion

CWDM and DWDM are both coming from the WDM technology that is capable of conveying multiple wavelengths in a single fiber. But with different characteristics, people should think twice before choosing the CWDM or DWDM system. CWDM usually costs less but its performance is far behind DWDM. Both your requirements and budget need to be taken into consideration. Moreover, the WDM products including CWDM mux/demux module, DWDM mux/demux module and optical splitter are highly welcome in the market.

Fiberstore Coarse Wavelength Division Multiplexing Devices

CWDM mux/demux is a flexible solution that enables operators make full use of available fiber bandwidth in local loop and enterprise architectures. The wavelengths used with CWDM implementations are defined by the ITU-T G.694.2, listing 18 wavelengths from 1270nm to 1610nm with 20nm increased. CWDM solution takes the most important advantage of low price which is typically 1/3rd lower than the equivalent DWDM optics. FS.COM introduces its new generation of coarse wavelength-division multiplexing (CWDM) devices boasting increased functions and improved performance to extend the reach of CWDM metropolitan networks. The following text will introduce CWDM Mux/Demux, CWDM OADM, and optical port configuration used in CWDM network.

FS.COM CWDM MUx/Demux

The CWDM Mux/Demux in FS.COM is a universal device capable of combining up to 18 optical signals into a fiber pair or 9 optical signals into a single fiber. It is designed to support a broad range of architectures, ranging from scalable point-to-point links to two fiber-protected rings.

Besides, FS.COM CWDM Mux/Demux is a passive device which allows for any protocol to be transported over the link, as long as it is at a specific wavelength (i.e. T1 over fiber at 1570nm transported alongside 10Gbps Ethernet at 1590nm). This allows for long-term future proofing of the networking infrastructure because the multiplexers simply refract light at any network speed, regardless of the protocol being deployed. The following image shows FS.COM 8 Channels 1470-1610nm Dual Fiber CWDM Mux Demux.

8 Channels 1470-1610nm Dual Fiber CWDM Mux Demux

FS.COM CWDM Mux/Demux With Different Optional Port Configurations

FS.COM also provides CWDM Mux/Demux with different optional port configurations such as, express port, monitor port, 1310nm pass band port and 1550nm port for these multiplexers according to customer choice.

  • Monitor Port: Our CWDM Mux/Demux is optional to equip with monitor port that allows our customer connect optical meter or OSA to monitor and troubleshoot the network. It is simple to operate. Add the monitor port to an existing, multiplexed link. A small sample, of each signal, is “leaked” to the outputs, then connect measurement/monitoring equipment, such as power meters or network analyzers, to the module outputs. When finished monitoring, disconnect the instruments. The network is left undisturbed. (Monitor port tap percentage is 5% as default.)
  • Expansion/Express Port: The Expansion Port (EXP) enables the cascading of two CWDM Mux/Demux modules, doubling the channel capacity on the common fiber link. For example, two 4-Channel MUX/DEMUX modules can be cascaded to create an 8-Channel fiber common link. (Express port isolation is 15dB as default.)
  • 1310 Pass Band Port: The 1310 pass band port allows a legacy 1310nm signal to pass through the CWDM MUX DEMUX module. The port can be used to combine an existing legacy 1310nm network with CWDM channels, allowing the CWDM channels to be overlaid on the same fiber pair as the existing 1310nm network. (Note: When you choose 1310nm pass band port, the CWDM 1310nm wavelength channel is NOT available on the CWDM MUX modules.) Besides, the 1310nm port can be used in this way as an optical supervisory channel (OSC) and its range is 1270nm-1350nm (1310nm±40nm). (Note: When you choose 1310nm pass band as an OSC, the available range of wavelength is 1370nm~1610nm on the CWDM MUX modules.)
  • 1550 pass band port: The 1550 pass band port allows a legacy 1550nm signal to pass through the CWDM Mux/Demux module. The 1550nm port can also be used in this way as an optical supervisory channel (OSC) and its range is 1510nm-1590nm (1550nm±40nm). When you choose 1550nm pass band as an OSC, the available range of wavelength is 1270nm~1490nm on the CWDM MUX modules.

Note: that standard (or native) 1310nm and 1550nm wavelengths are not the same as CWDM 1310nm and CWDM 1550nm wavelengths. The center wavelength tolerances for legacy 1310nm and 1550nm are much wider than the CWDM equivalents, and therefore not precise enough to run through CWDM filters. When implementing a CWDM network, a standard wavelength can be converted to CWDM wavelength, or a CWDM Mux with a pass band port can overlay the standard wavelength onto the CWDM common link. A pass band port is an additional channel port on a CWDM MUX that allows a legacy 1310nm or 1550nm signal to pass through the network within a reserved band. The legacy device is connected directly to the pass band port via fiber cabling. Standard wavelengths can be converted to CWDM wavelengths using CWDM Small Form Pluggable (SFP) transceivers, transponders, and media converters that support SFPs.

FS.COM CWDM OADM

Since adding new fiber optic cables for signal transmission of the devices would cost too much, IT managers would turn to use OADM in CWDM network, which can couple two or more wavelengths into a single fiber as well as the reverse process, saving a lot of money and installation time when they want to add or drop signal on a single fiber. FS.COM provides a wide selection of CWDM OADM which can add or drop fiber count of 1, 2 and 4. And these OADMs can be categorized into three type with different package form factors: plug-in module, pigtailed ABS box and rack mount chassis. The plug-in modules can be installed in empty rack enclosures. Three CWDM OADM types with different package form factors are shown below.

plug-in module, pigtailed ABS box and rack mount chassis

Conclusion

CWDM is a popular technology which can provide cost-effective solutions for users to upgrade their network using the least fiber strands. FS.COM provides a series of devices used in CWDM network, like CWDM Mux/Demux with different optical port configurations, CWDM OADMs, CWDM transceiver modules, etc. For any requirement, please visit FS.COM.