With the need for bandwidth increases, the WDM (wavelength division multiplexing) technology was developed to expand network capacity over a single fiber. It uses a multiplexer (Mux) at the transmitter to combine several signals together, and a demultiplexer (DeMux) at the receiver to split them apart. Most WDM systems operate on 9µm single-mode fiber optical cables. And they are divided into CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). This article mainly focuses on CWDM system.
CWDM is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths/colors of laser light to carry different signals. In a CWDM system, the CWDM Mux/DeMux is one of the most important component.
The CWDM Mux/DeMux modules are passive optical solutions which are easy to operate with a reliable low-maintenance design, and do not use power supplies or electronics. They are designed to provide optical networking support for high-speed Fibre Channel and Ethernet communication for MAN (metropolitan area network) over a grid of CWDM optical wavelengths. CWDM Mux/DeMux is capable of multiplexing and demultiplexing wavelengths up to 18 channels from 1270 nm to 1610 nm in 20nm increments. Moreover, it works seamlessly with transceivers to optimize link length, signal integrity and network cost, and can be incorporated into a single rack-mount solution for enhanced design, power and space efficiency.
Typically, the CWDM Mux/DeMux modules interface to CWDM SFP/SFP+/XFP transceivers on an attached FC SAN or network device. This chassis-based system allows the addition of CWDM capability to any existing SAN or network device that supports LC SFP/SFP+/XFP transceivers. In short, the CWDM Mux/DeMux modules are connected with CWDM SFP/SFP+/XFP transceivers which are inserted into the switch SFP/SFP+/XFP ports by using LC single-mode patch cables.
The CWDM transceivers are hot-swappable, field-replaceable devices that adopt an electronic data signal to laser light at a specific wavelength. Moreover, they are color-coded to indicate the wavelength and have a color-coded clasp at one end. So the CWDM Mux/DeMux should be connected with the CWDM transceivers with the same wavelength as each transceiver will work only at the appropriate port and the data will always flow between devices with the same wavelengths. For instance, the port on the CWDM Mux/DeMux marked with 1470 nm, should be connected with the CWDM transceiver that works over 1470nm wavelength. As CWDM Mux/DeMux supports up to 18 different wavelengths, there are CWDM transceivers working over these 18 wavelengths. The following table lists the 1000BASE-CWDM SFP (20km) transceivers as an example.
| Model ID | Wavelength | Description |
| 33979 | 1270 nm | 1000BASE-CWDM SFP 1270nm 20km DOM Transceiver |
| 37319 | 1290 nm | 1000BASE-CWDM SFP 1290nm 20km DOM Transceiver |
| 37321 | 1310 nm | 1000BASE-CWDM SFP 1310nm 20km DOM Transceiver |
| 37320 | 1330 nm | 1000BASE-CWDM SFP 1330nm 20km DOM Transceiver |
| 52674 | 1350 nm | 1000BASE-CWDM SFP 1350nm 20km DOM Transceiver |
| 52675 | 1370 nm | 1000BASE-CWDM SFP 1370nm 20km DOM Transceiver |
| 52676 | 1390 nm | 1000BASE-CWDM SFP 1390nm 20km DOM Transceiver |
| 52677 | 1410 nm | 1000BASE-CWDM SFP 1410nm 20km DOM Transceiver |
| 52678 | 1430 nm | 1000BASE-CWDM SFP 1430nm 20km DOM Transceiver |
| 52679 | 1450 nm | 1000BASE-CWDM SFP 1450nm 20km DOM Transceiver |
| 52680 | 1470 nm | 1000BASE-CWDM SFP 1470nm 20km DOM Transceiver |
| 52681 | 1490 nm | 1000BASE-CWDM SFP 1490nm 20km DOM Transceiver |
| 52682 | 1510 nm | 1000BASE-CWDM SFP 1510nm 20km DOM Transceiver |
| 52683 | 1530 nm | 1000BASE-CWDM SFP 1530nm 20km DOM Transceiver |
| 52684 | 1550 nm | 1000BASE-CWDM SFP 1550nm 20km DOM Transceiver |
| 52685 | 1570 nm | 1000BASE-CWDM SFP 1570nm 20km DOM Transceiver |
| 52686 | 1590 nm | 1000BASE-CWDM SFP 1590nm 20km DOM Transceiver |
| 52687 | 1610 nm | 1000BASE-CWDM SFP 1610nm 20km DOM Transceiver |
FMU CWDM Mux/DeMux modules are new types of modules launched by FS.COM. Compared with the traditional CWDM Mux/DeMux modules, the new FMU series modules are more user-friendly and show completely new characteristics.
With low-profile modular design, the FMU CWDM Mux/DeMux modules plug into one half of a 1RU, 19” rack mount chassis for simple installation and modularity. This chassis-based system allows a network equipment manufacture to add CWDM capability to any existing networks with simple pluggable interface. Besides, the equipment ports of the FMU CWDM Mux/DeMux modules are color-coded to match the wavelengths of CWDM transceivers to simplify installation and troubleshooting without having to remove the transceivers from the local equipment. This color-coded feature is the major advantage of this new FMU series modules and it do greatly simplify the process of connecting a CWDM transceiver to its associated device port. The following picture is an example of 8 channels 1470-1610nm dual fiber CWDM Mux/DeMux. This new FMU series CWDM Mux/DeMux modules deliver dramatic cost savings to network equipment manufacturers, enabling them to develop metro access systems that are lower in cost, easier to provision and simpler to operate.
The following table lists FS.COM FMU series CWDM Mux/DeMux modules.
| Model ID | Description |
| 43554 | 4 channels 1470-1590nm single fiber CWDM Mux Demux |
| 43553 | 4 channels 1490-1610nm single fiber CWDM Mux Demux |
| 42972 | 4 channels 1270-1330nm dual fiber CWDM Mux Demux |
| 42944 | 4 channels 1510-1570nm dual fiber CWDM Mux Demux |
| 43780 | 8 channels 1290-1590nm single fiber CWDM Mux Demux |
| 43779 | 8 channels 1310-1610nm single fiber CWDM Mux Demux |
| 42945 | 8 channels 1290-1430nm dual fiber CWDM Mux Demux |
| 43097 | 8 channels 1470-1610nm dual fiber CWDM Mux Demux |
| 43711 | 9 channels 1270-1590nm single fiber CWDM Mux Demux |
| 43699 | 9 channels 1290-1610nm single fiber CWDM Mux Demux |
| 48393 | 4 channels 1470-1590nm single fiber CWDM Mux Demux with expansion port |
| 48394 | 4 channels 1490-1610nm single fiber CWDM Mux Demux with expansion port |
| 42973 | 4 channels 1510-1570nm dual fiber CWDM Mux Demux with expansion port |
| 43099 | 8 channels 1470-1610nm dual fiber CWDM Mux Demux with expansion port |
| 33489 | 18 channels 1270-1610nm dual fiber CWDM Mux Demux with monitor port |
| 30408 | 1RU Rack Mount Chassis unloaded, holds up to 2 units half 19”/1RU FMU Cassettes |
Note: The modules with expansion port allows adding or expanding more CWDM wavelengths/channels to the network for future upgrade. If used, it will be treated just like the other ports and up-jacketed and terminated as needed. If not used, it will be cut back into the module and terminated in a way to reduce reflections.
Both the traditional CWDM Mux/DeMux and the FMU series CWDM Mux/DeMux are used to increase fiber network capacity without the expense of deploying more fiber cables. They make full use of the low loss bandwidth of optical fiber to achieve ultra-high bit rate transmission. The key difference is that it is more convenient and efficient for the FMU CWDM Mux/DeMux to connect with the CWDM transceivers. FS.COM provides both the two kinds of CWDM Mux/DeMux modules. For more details, you can visit www.fs.com.