CWDM BiDi Transceivers

Due to shortage of fibers and higher pricings of rental of dark fiber the CWDM Bidi techniques are gaining popularity. In many cases companies have to rent fiber from a bigger telco or the owner of the dark fiber is the national telecom provider which in a way is the competitor of that company. Another factor is that CWDM BIDI requires less fusion splicing and patches. Making pigtails/connectors on the bare fiber can be an important cost factor for a Fttb project.

There are different techniques and possibilities to communicate over one single fiber in stead of a traditionally dual fiber communication. The most important thing is to know why the “normal” communication cannot be archieved over 1 single fiber. This has to do with the fact that the normal receiver detect all the light there is so also it’s own back reflection. Every normal UPC patch reflect some light and if the Sender and receiver are on the same fiber the receiver will get the signal from the other transceiver as well as it’s own back reflection. This the reason why the normal 100mbit/1G/10G bidi’s are working on 2 wavelength.  One side is sending red light and blocking incoming red light, the other side is sending blue and blocking incoming blue.

CWDM BiDi explaining lasers

This is a technique which is worldwide used in Fiber to the Home projects and this will work fine with a single 100mbit/1G/10G connection but not multiple connections. To achieve this you can use different techniques. At this moment there are 3 proven techniques which are deployed to multiplex multiple channels over one single fiber. These 3 methods are:

-        Use traditional CWDM/DWDM and cross patch them

-        Use CWDM BIDI with APC so less backreflection

-        Use CWDM BIDI’s which sends 2 different wavelength inside one CWDM window

All the advantages and disadvantages are seen in this presentation. Please note that Solid Optics always investigates new products and techniques and some of them are not ready mentioned in this presentation. Please contact us with your “challenge” and our technical sales team can assist you.



Most techniques are based on CWDM, this has to do with the fact that this technique is more stable in outdoor techniques with high temperature fluctuations (-40 / +85). We have extensive knowledge on these techniques and can assist you in which will assist you the best.


Here under you can see the 3 different techniques in reality. We show how easy it is to deploy the different techniques.

CWDM BiDi with crossconnect CWDM BiDi with APC connectors CWDM BiDi with UPC connectors