Bidirectional RoF system

[Tayyab Mehmood]

Hi, I am confused with the selection of number of iterations and initial delay for the bidirectional fiber link, although I am getting satisfactory results at the downlink but could not get the any kind of results at the uplink side.

I also go through the last post of Mr. shahid (simple Bi-diectional link) and the Lesson 5: Bidirectional Simulation — Working with Multiple Iterations (Optical System).

would anyone have any idea how exactly configure the parameters in signals tab?
I attached the project file too.

[Damian Marek]

When I run the simulation I get output at both ends, but the results are not very good. Take a look at the screenshot I took at the input to one of your receiver sections. The noise (green line) is much larger than the modulated signal, which are the 8 smaller peaks at the bottom. The optical carrier is large, but it is not really what is carrying the information.

I would suggest starting with a simpler project maybe only one upstream and just a null signal for the downstream signal and see if you can get the proper amplifier sizes and parameters to get a good transmission.

Regards

[Ashu verma]

As Damian said ,start with simpler projects.Use sample file given by optiwave and then make changes to it according to you by checking at each step.Screen shot attached by damian explained well by Damian.You can choose any of the example there are some examples such as XGPON,WDM-PON,BPON etc.You can get help from the forum topic you have mentioned above.

[Tayyab Mehmood]

Thanks Damian Marek and Sam Sung, I am simplifying the project according to the Damian suggestions and trying to choose parameters to get best transmission results at both ends of Bidirectional fiber. I am also checking the examples described by Sam and upload the simpler project file shortly.

[Tayyab Mehmood]

Sir Damian the snapshot you attached in your last post is after the amplifier for uplink, if I am right then I use 193.2 & 193.175 THz CW laser for uplink but the spectrum shows the wavelengths of 193.1 and 193.125 THz.

[alistu]

Hi Tayyab, Damian mentioned that the optical carrier is large, but it is not really what is carrying the information, whereas the CW laser frequencies you have chosen are the ones who are supposed to be carrying the information. Could you please upload the file in which you have made the changes? Thank you.

[Tayyab Mehmood]

Respected Sir I simplified the project file (attached below) and run again, now I get satisfactory results for downlink at 1 and 2 as shown in the figure # 01 (attached below).

[Tayyab Mehmood]

Thanks for replying, but sir problem starts with the uplink, why I am getting the remaining of 193.1 & 193.25 THz at 5 and at 6 ( attached below) and not getting any result at 3 and 4.

[alistu]

I am sorry I have spent some time trying to find the problem but I did not manage. Yet I believe there is some problem with the symmetry of the design. You see, I exchanged the laser power values (the ones from uplink with the ones from downlink) and just the frequencies from downlink are again there in spectrum analyzers (I mean 193.15 and 193.175). I will let you know if I make any progress.

[Tayyab Mehmood]

Thanks Alistu, I am also working on it and trying to modify the examples related to bidirectional fiber to run this simple bidirectional ROF link.

[Tayyab Mehmood]

Respected Sir , checkout the attached files below , I modify the project file and remove optical circulators from both sides , now I get the desired results.

kindly see the figure, which shows the spectrum after the amplifier for uplink and downlink.

[alistu]

I took a look at the screenshots and it seems that the problem with the frequencies is no more there. I am glad that the problem seems to have been solved. As I mentioned earlier, just exchanging frequencies showed there was a problem with the symmetry and you eliminated the right components (in this regard).

Cheers!

[Tayyab Mehmood]

Thanks sir

[alistu]

You’re welcome Tayyab! And please don’t hesitate to ask in case of any other trouble you might face in your simulations.

[Tayyab Mehmood]

Thanks Sir.

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