What Is WDM ? How Wavelength Division Multiplexer Works In CATV Industry for GPON & EPON Solutions ?

what is wdm


In cable tv industry when the things comes in terms of EPON & GPON solutions then technique Wavelength Division Multiplexing is used. Wavelength Division Multiplexer is the device to be implemented for this solution.

So in this article we will briefly understand What exactly is Wavelength Division Multiplexing ? How WDM is used in CATV industry ? etc.

What Is Wavelength Division Multiplexer ?

wavelength division multiplexer

As we have discussed above Wavelength Division Multiplexer uses the Wavelength Division Multiplexing Technique.

Wavelength Division Multiplexing is used to send different Data Streams on a single fiber at different wavelength. These Data Streams can be Video , Data and Voice.

Basically there are two types of Wavelength Division Multiplexing known as CWDM and DWDM. CWDM stands for Course Wavelength Division Multiplexing and DWDM stands for Dense Wavelength Division Multiplexing.

So Wavelength Division Multiplexer is a passive optical device used at the Headend side to send Data , Voice and CATV simultaneously in a single fiber at different wavelength.

At the receiving end Wavelength Division Demultiplexer is used to seperate these wavelength in different core of fiber to receive it.

How Wavelength Division Multiplexer Works ?

wavelength division multiplexing working

The phenomenon of WDM is based on the coupler and prism (WDM Demultiplexer). As shown above in the figure there are different colors of lights which goes into the coupler.

This coupler gives the single core fiber output. In which all colors are combined together to send it.

At the receiving end a prism is installed. Which gets the single input through single fiber which can be called as a white light.

Now as per properties of prism if a prism gets a white light then it reflect the different color at different angles as shown in the figure above.

Here different Data Streams are the different colors of light. Then White light can be called as combined signal at different wavelength. At the receiving end like prism properties different data streams are recovered from single core fiber.

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How WDM Implemented In GPON Solutions ?

wdm gpon solution working

WDM plays a very important role in EPON and GOPN solution. As shown above in the figure WDM is installed after OLT and EDFA. Where EDFA gives the CATV input at 1550 nm wavelength to WDM. While OLT gives Data / Voice input at 1310 nm to WDM.

Here 1310 nm wavelength works as Downstream while 1490 nm wavelength works as Upstream.

Now WDM combine these different wavelength of data streams and provides the single output of optical fiber.

At the receiving end a ONU or ONT is installed. Which takes these combined data streams and provides different output wavelength for different applications like Data, Voice and CATV.

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In the ONU there is RF output port for CATV services and RJ45 jack for internet services. Also a dedicated slot for Telephone services.

Thus there are different kind of ONU and ONT devices deployed as per user requirement of services like Voice , Data and CATV.

The benefit of WDM technology is that you now no need to carry individual fiber for different kind of services like Data , Voice and Video. It reduces the cost of fiber , complexity of fiber, Maintenance of fiber and power consumption too.

What Are Benefits Of WDM Technology ?

(1) It reduces the cost of fiber so low cost solution.

(2) It reduces the maintenance Of Fiber.

(3) It reduces the complexity of Network.

(4) It Save the power consumption.


Wavelength Division Multiplexer is the passive optical device used in Tripple Play solutions. Which enable the subscriber for Voice , Data and CATV services simultaneously.

Earlier it was very expensive to deploy the WDM technique but now there are low cost solutions available in the market.

Wavelength Division Multiplexing Technology made this low cost solution.

Suggested Articles

What Is GPON Working ? Explain In Brief ?

What Is ONU ? How ONU Works ?

What Is AON and PON ?

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