How to Build DWDM Network Over CWDM Network

Using CWDM MUX/DEMUX has been widely accepted as the most cost-effective and time-save method to increase the existing fiber optic network without adding optical fibers. However, a CWDM network can only support up to 18 different wavelengths. Is there any possibility to increase the capacity of the existing CWDM network? Hybrid CWDM and DWDM network is being introduced to combine the DWDM wavelengths with the existing CWDM wavelengths.

Combing DWDM With CWDM to Increase Network Capacity

As we know the CWDM wavelengths ranging from 1260nm-1625nm with space channel of 20nm actually cover all the range of DWDM wavelengths (ranging from 1470nm to 1625nm). However, DWDM wavelengths have much smaller channel spaces (0.4nm/0.8nm/1.6nm) and can provide larger bandwidth than that of the CWDM wavelengths. To combine DWDM with CWDM, the CWDM wavelengths that are near DWDM wavelengths can be used to transmit the DWDM wavelengths. However, not all these CWDM wavelengths are suggested. Generally, wavelengths of 1530nm and 1550nm are used to combine the CWDM and DWDM network together. Similarly, not all the DWDM wavelengths are suggested to be combined with CWDM network. The following picture shows DWDM wavelengths that are suggested to be combined with 1530nm and 1550nm.

CWDM DWDM hybrid wavelengths

How to connect CWDM With DWDM

To combine the DWDM wavelengths with CWDM wavelengths, both CWDM MUX/DEMUX and DWDM MUX/DEMUXs should be used. The following picture shows the connection methods for hybrid CWDM and DWDM. On both ends of the fiber link, a CWDM MUX/DEMUX and a DWDM MUX/DEMUX with corresponding wavelengths are deployed. Connect the line port of the DWDM MUX/DEMUX to the 1530nm/1550nm channel port of the CWDM MUX/DEMUX, the DWDM wavelengths can be added to the existing CWDM network.


Easier Operation and Cabling Solution for Hybrid CWDM and DWDM

In the CWDM and DWDM Hybrid network, the CWDM MUX/DEMUX and DWDM MUX/DEMUX play the most important roles. To offer better operation and cabling environment for these WDM MUX/DEMUX, FMU series products which are developed by FS.COM has been introduced. This series of products combines the MUX/DEMUX into half-U plug-in modules, and installed in 1U rack for better cable management and network operation as shown in the following picture.

FMU DWDM over CWDM solution

For CWDM and DWDM hybrid network, a FMU CWDM MUX/DEMUX and a DWDM half-U plug-in module can be installed together in a FMU 1U rack chassis. Thus, the two modules can be linked together easily. Meanwhile, with clear port identification, the management and operation of the fiber optic network would be easier.


The CWDM network can be added with DWDM wavelengths by the using of CWDM MUX/DEMUX and DWDM MUX/DEMUX which support corresponding wavelengths. The DWDM wavelengths that are 6.5nm around 1530nm and 1550nm are suggested to be used for CWDM and DWDM hybrid network. For better network operation and cabling, FMU series WDM solutions are suggested, which can provide easier and more flexible connections between CWDM MUX/DEMUX and DWDM MUX/DEMUX. Kindly contact for more details about DWDM over CWDM solution, if you are interested.

Source: How to Achieve DWDM Over CWDM

1310nm, 1550nm, Expansion and Monitor Ports on CWDM MUX/DEMUX

CWDM technologies have been widely accepted low cost and fast solutions to increase capacity of the existing fiber optic network without adding new fibers. To add more beneficial to CWDM networks, CWDM MUX/DEMUX, which is used to multiplexing and demultiplexing optical signals, is being added with special ports like expansion port, monitor port, 1310nm port and 1550nm port. What’s the function of these special port? Do you really need them on your CWDM MUX/DEMUX? This post will offer details about these special ports for your references.

1310nm, monitor port and expansion port

Special 1310nm Port and 1550nm Port on CWDM MUX/DEMUX

CWDM utilizes usually wavelength range from 1270nm to 1610nm with a channel space of 20nm, which means the 1310nm and 1550nm are also the CWDM wavelengths. A full channel CWDM MUX/DEMUX can have 18 channels using 1310nm and 1550nm as channel ports. Actually, in most cases, 1310nm and 1550nm are used as channel port in CWDM MUX/DEMUX. They should be connected to the corresponding colored CWDM fiber optic transceiver, like CWDM 1310nm SFP and CWDM 1550nm SFP+.

As 1310nm and 1550nm are usually used for long distance transmission in normal fiber optic network. Most long distance fiber optic transceivers are designed to work over 1310nm and 1550nm. For example, 10G SFP+ LR transceiver is working over 1310nm and 10G SFP+ ZR is working over 1550nm. The Special 1310nm port and 1550nm port on CWDM MUX/DEMUX can be directly connected to these transceivers to expand the capacity of CWDM network. This is the main function of the 1310nm and 1550nm ports on CWDM MUX/DEMUX.


However, the special 1310nm and 155nm ports can affect the transmission of the wavelengths near it. The two port cannot be added freely. If you want to add 1310nm or 1550nm ports on your CWDM MUX/DEMUX, wavelengths which are 0-40 nm higher or lower than 1310 nm or 1550 nm cannot be added to the MUX. The following shows the ports that you can add on your CWDM MUX/DEMUX in different cases.

  • If you add 1310nm port, the following ports can be added: 1370nm, 1390nm, 1410nm, 1430nm, 1450nm, 1470nm, 1490nm, 1510nm, 1530nm, 1550nm, 1570nm, 1590nm, 1610nm
  • If you add 1550nm port, the following ports can be added: 1270nm, 1290nm, 1310nm, 1330nn, 1350nm, 1370nm, 1390nm, 1410nm, 1450nm, 1470nm, 1490nm
  • If you add both 1310nm port and 1550 port, the following ports can be added: 1270nm, 1290nm, 1310nm, 1350nm, 1510nm, 1530nm, 1550nm, 1570nm, 1590nm
Expansion Port on CWDM MUX/DEMUX

Although CWDM has 18 channels that can be used for transmission, in many cases, not all these channels are needed at one time or when the CWDM network deployed. But once you want to add more wavelengths to the existing CWDM network, the expansion port on CWDM MUX/DEMUX will play an important role, which can combine two individual CWDM MUX/DEMUXs with different wavelengths as one CWDM MUX/DEMUX.

CWDM MUX/DEMUX with expansion port

Here takes this 16-channel FS.COM FMU CWDM MUX/DEMUX as an example. There are two half-U plug-in CWDM MUX/DEMUXs deployed in a 1U rack. The module on the left side has an additional expansion ports. If you connect the expansion port with the line port on CWDM MUX/DEMUX on the right side. The two CWDM MUX/DEMUXs can work as one. This is the magic of the expansion port. If your network hasn’t used all the CWDM channel and you can to add more in the future, you can buy add an expansion port on your MUX/DEMUX or add the expansion port on the new CWDM MUX/DEMUX in the future.

Monitor Port on the CWDM MUX/DEMUX

Unlike the above mentioned three special ports which can increase the capacity of the CWDM network, the monitor port literally is used for monitoring the CWDM network. In many cases, the monitor port is necessary which can simplify turn-up operations of CWDM networks, and can be used for in-service monitoring of the CWDM signals by connecting an optical spectrum analyzer or a power meter.

4-channel CWDM with monitor port


The 1310nm port, 1550nm port and expansion port are designed to increase the capacity of CWDM network. The Monitoring port is added for better network management and operation. Except the 1550nm port, all these port can also be added on the DWDM Mux/DEMUX and play the same function. Kindly visit WDM page for full series of CWDM and DWDM solutions, if you are interested.

How to Use Optical Power Meter

To ensure the signal transmission quality in fiber optic network, optical power should be well controlled. Optical power should not be too high or too low. And it should be within the scope of the device’s requirement. To achieve accurate measurement, optical power meter is usually used to test the optical power. It is easy to use and can be really helpful during fiber optic network installation and maintenance.

Buttons on Optical Power Meter

The functions and operation of optical power meters provided by the market are similar. Generally there are four buttons on the optical power meter: power button, dBm/w button, REF button and λ button. The functions of these buttons are listed in the following:

  • Power button: turn the power meter on or off;
  • dBm/w button: shift between linear (mW) mode and logarithmic (dBm) mode;
  • REF button: press this button to set the current measured power as the referent point;
  • λ button: select the calibrated wavelength. The most commonly used wavelengths are 850nm, 980nm, 1310nm, and 1550nm.

Here takes an example of a typical handheld optical power meter (FOPM-104) which is designed by FS.COM as shown in the following picture.optical power meter

Adapter Type of Optical Power Meter

To use the optical power meter, a length of fiber optic patch cable is usually required to connect the optical power meter interface and the interface of devices requiring test. For instance, if the interface on the optical power meter is FC, the device for testing has a LC interface. Then a length of FC-LC fiber patch cable is needed. Some of the optical power meters have only one fixed optical interface. Some can provide replaceable optical adapter to fit different patch cables. The above mentioned FOPM-104 handheld optical power meter provides three type adapters: SC, FC and ST (as shown in the following picture).optical power meter adapter

For testing of fiber optic interface like LC, SC, ST and FC, this above power meter is enough. Some optical power meter might have two optical interfaces for common connectors. However, interface like MTP/MPO, optical power meter with special interface should be used. The following picture shows a MTP optical power meter provided by FS.COM, which can be used to test devices or components with MTP interfaces like 40G SR4 QSFP+ transceiver.MTP optical power meter

Optical Power Measurement Using Optical Power Meter

The using the optical power meter is simple. The following video will take the example of 10G-LR SFP+ Cisco compatible module to illustrate how to use an optical power meter for testing. This cisco compatible transceiver will be inserted in Cisco Nexus 9396PX switch. A length of single-mode LC-FC fiber patch cable is required. This is because 10G-LR SFP+ transceiver is a single-mode transceiver working on wavelength of 1310nm. After the optical power meter is connected to the module. Turn on the power button and press λ button to select 1310nm wavelength. At first the power value will change rapidly, then it slows down until still. The final power value will be shown on the screen.

Kindly visit Optical Power Meter page or contact for more details.

How to Use OADM in WDM Network

Adding or Dropping signals of devices on the existing WDM network is very common to service providers. Adding a new fiber optic cable for signal transmission of the devices would cost too much. The using of OADM (Optical Add-Drop Multiplexer) solves this problem easily. A OADM can couple two or more wavelengths into a single fiber as well as the reverse process. Service providers can save a lot of money and installation time by adding OADM into the existing WDM network, if they want to add or drop signal on a single fiber.

WDM Solution

Types and Selection of OADM

OADM is generally deployed in WDM network which includes CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing). Thus, OADM can also be divided into CWDM OADM and DWDM OADM according to its applications. During the selection of OADM, the fiber count that a OADM should be considered. The most commonly used CWDM OADM can add or drop fiber count of 1, 2 and 4. For DWDM OADM, the fiber counts are usually 1, 2, 4 and 8. The installation environment should also be considered during the selection of OADM. There are mainly three types of OADM 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. The following shows three CWDM OADM with different package form factor.

 4-channel OADM plug-in module  4-channel rack OADM  4-channel pigtailed oadm
Plug-in module OADM Rack mount OADM Pigtailed ABS box OADM
How to Connect OADM With WDM MUX/DEMUX

In most cases, OADM is deployed with CWDM or DWDM MUX/DEMUX. It is usually installed in a fiber optic link between two WDM MUX/DEMUXs. The following picture shows a CWDM network using a 1-channel dual fiber OADM between two CWDM MUX/DEMUXs. Signals over 1470 nm are required to be added to and dropped from the dual fiber link. On the OADM, there are usually one port for input and one port for output. The OADM can be regarded as a length of fiber cable in the fiber link. The point is the one or more strand of signals is added or dropped when the light goes through the OADM.

1-channel OADM

To better illustrate the using of OADM. Here takes the example of a 4-Channel CWDM OADM. This 4-channel OADM supports wavelengths of 1470nm, 1490nm, 1510nm and 1530nm. West port is connected to a CWDM MUX/DEMUX and the East port in connected to the other CWDM MUX/DEMUX on the other end of this fiber link. Up to 4 different wavelengths of optical signals can be added or dropped. The four Channel ports can be connected to the corresponding CWDM transceivers installed on switches. Then a CWDM fiber link with OADM is finished.

4-channel OADM

OADM Solution

OADM is a cost-effective and easy to use passive fiber optic component, which can provide easy to build and grow connectivity environment for WDM network. FS.COM provides full series of WDM MUX/DEMUX and CWDM OADM and DWDM OADM. Kindly contact for more details.

Add More Beneficial to Fiber Patch Cables

More and more fiber optic cables are adding to the existing fiber optic network. Technicians are facing the challenges to detail with thousands or more fiber patch cables. Well organized fiber patch cable and fiber cabling system are no longer enough for the increasing need. The fiber patch cables used in data centers should still have reliable and stable performance under repeat connections and disconnections. To find the best solution for fiber patch cables in high density data center and server room. The most urgent current demands should be considered.

fiber cabling problems

How to Solve Fiber Cabling Problems

There are mainly two problems in data center for fiber cabling. One is too many fiber cables installed in limited spaces. The other one is the property of fiber optic cable which requires careful operation during cabling.

high density fiber cabling
Decrease Fiber Patch Cable Space Requirement With Uniboot Design

As more and more devices are added in data center, decrease fiber count in data center is not that easy. Thus, decrease the space requirement for each fiber optic patch cable is relatively easier. Decrease cable diameter is suggested. Smaller fiber cable diameter is preferred in data center now. New versions of duplex fiber patch cables like LC uniboot fiber patch cables are invented. The following picture shows one end of the LC uniboot fiber patch cable. This type of duplex fiber cable has a smaller cable diameter than that of traditional duplex zipcord fiber cable. And the uniboot design has lower space requirement for connector boot.

LC uniboot fiber patch cable
Provide Easier Finger Access With Push Pull Tab

However, even the sizes of the fiber cable and connector boot are decreased. The port type like LC, SC and MTP cannot be changed directly. There is still finger access problem at the device port is the devices like switches and fiber enclosure are fully loaded with fiber patch cables. Then a push pull tab is being added to the connector body. The following picture shows the details of LC uniboot fiber patch cable with push-pull tab.

LC push-pull fiber patch cable

With the help of this small but useful push-pull tab, data center technicians not only have easier access to every port, but also enjoy easier connecting and disconnecting of every individual fiber patch cable in high density cabling environment without affecting any other fiber links near it. There is also high density push-pull MTP-LC breakout cable available in FS.COM.

push-pull MTP-LC fiber patch cable
Use Bend Insensitive Fiber Cable for Flexible Cabling

Data center technicians are required to operate the fiber patch cables very carefully to decrease the bend loss. The using of bend insensitive fiber cable can offer a much flexible and easy cabling environment for the data center technicians. The worrying of bend loss can be eliminated.

bend insensitive fiber patch cable

All Benefits in One Fiber Patch Cable

As the above mentioned, to build a high density cabling environment, uniboot fiber patch cable and high density push-pull tab fiber patch cables are being invented. To offer an easier and flexible cabling environment with high performance, bend insensitive fiber cables are suggested. What if we add all these great advantages into a single length of fiber patch cable? Here introduces the very special but useful LC bend insensitive uniboot fiber patch cable with push-pull tab (shown in the following picture).

LC bend insensitive uniboot fiber patch cable

This LC uniboot fiber patch cable has all the above mentioned advantages for space saving, easy finger access and flexible cabling with lowest bend loss. These LC uniboot fiber patch cables of different fiber types and cable lengths are available in FS.COM. If you are looking for some fiber patch cables to add more beneficial to your data center, you can consider this LC Push-Pull bend insensitive uniboot fiber patch cable.