DWDM system

[burhan num mina llah]

Hello all

I tried to copy the existing example of 32 channel DWDM system system for only 4 channels and kept all the characteristics similar to those mentioned in the example itself.. But I don’t get any result at the output. Can anybody please help me with it..

[Dr. Dhiman Kakati]

Hello burhan num mina llah,
All you need to do is as follows:

keep all the bandwidth constant as previous,

check the CW laser array for frequency and power (keep power sweep mode as previously), Check frequency (or wavelength) range and set the middle frequency (among all the generated light frequencies) as the single mode fiber (SMF) and for also dispersion compensating fiber (DCF) at the properties of the fiber.

check power at different positions such as at the WDM mux output, after SMF, after DCF and after the WDM demux, dont let it go high or to low below a certain level.

Thats all you need to do and you will get a better output in terms of constellation and Eye diagram, BER.

Regards,
Dhiman

[burhan num mina llah]

Hi Dhiman Kakati

Thankyou very much .. I don’t have access to license this time but tomorrow i will try to implement all your suggestions and let you know if i got the required results.. I hope it works after all these changes like keeping middle frequency that of SMF and DCF as suggested by you .. Again thanking you..

Regards

Burhan

[Dr. Dhiman Kakati]

Hi Burhan,
you are most welcome, I think, This should definitely work, just 2days before I tried another system from 16 channel I made it 4 channel. and let me know if you face any further issue. how much is your wavelength spacing at the transmitter side. and one more thing you try to make the spectrum at the WDM MUX output.

Regards,
Dhiman

[aasif bashir dar]

Hello burhan num mina llah madam
c;lick on the fiber properties and unclick the option of reference frequency,,,as it will by default take the value for centra frequency.
bandwidth should be constant , CW laser array frequency and power ( as previously), Check frequency (or wavelength) range and f

and as dhimen said
“check power at different positions such as at the WDM mux output, after SMF, after DCF and after the WDM demux, dont let it go high or to low below a certain level.”

with Regards,

[aasif bashir dar]

hi burhan num mina llah madam
User defined reference wavelength
If TRUE, frequency value of “Reference wavelength” is used internally as ‘zero’ (or reference) frequency in spectrum of signal envelope. Values of parameters (attenuation, dispersion) are assumed to correspond to this frequency. If parameters are wavelength-dependent (from files), they are evaluated at this frequency. If FALSE, central frequency of simulated band is use..
with regards

[Atul Sharma]

Thanks aasif for suggestions you have provided. I think this should help Burhan.

[SAHIL SINGH]

Hello burhan num mina llah,

I agree with the viewpoint of asif click on the fiber properties and unclick the option of reference frequency…Also as mentioned in the previous comments do make a note of the power at different positions particularly at the WDM mux output.. Hope it helps

with Regards
Sahil Singh

[Atul Sharma]

Hello Burhan. Greetings from my side.

I think a relevant question was posted recently not exact the same but it was related to down conversion of the 32 channel WDM system to 4 channel WDM system. You may check the forum posts to find and i feel it will be of great help.

Regards
Atul Sharma

[umer syed]

i agree with dhimen sir and aasif here…
If , “Reference wavelength” is used ,, Values of parameters (attenuation, dispersion) are assumed to correspond to this frequency. If parameters are wavelength-dependent (from files), they are evaluated at this frequency. Ifnot clicked, central frequency of simulated band is use..

with regards

[Atul Sharma]

Hello Umer Syed.

Your statement is confusing. It seems you are saying same thing twice.

Regards
Atul Sharma

[Ranjeet Kumar]

Hi Burhan ma’m
First check the CW laser power as being suggested by Dhiman by increasing the laser power to few dbm.
Next vary the tranmsmission channel spacing by varying the frequency of laser, i think standard channel spacing are: 25 ghz, 50 ghz, 75 ghz and 100 ghz. Usually We find difficulty in designing very dense WDM system (channel spacing of 25 ghz).
Check for Wdm mux bandwidth , filter order if you are not using ideal mux.
Now go step by step as Dhiman described above.
Vary no. loops of fiber because for small laser power WDM system gives no results at very large transmission length.
Seeking your response.

Thanks and regards
Ranjeet

[burhan num mina llah]

Hi All

Thanks for all the responses. But i am still getting the same result. for better understanding of the issues i am having with my model i am uploading the .osd file of respective model. please i request you all to take a look at the file and suggest me what should i further do to improve the result.

Regards

Burhan

[Dr. Dhiman Kakati]

Hello burhan num mina llah,
you missed out something thats why the output is not as expected, I am Unable to open your design attached attached here, I think it is made on optisystem 14 and as I am using Optisystem V13 so will you please tell me the exact name of the file and respective folder in which you are trying to modify, Thanking you.

With regards,
Dhiman

[Dr. Dhiman Kakati]

Hi burhan num mina llah,
I tried to modify the 32 channel WDM NRZ system i.e. the ideal one but it was very simple to implement for 4 channel. I did the following modifications.

1. kept all the fiber property constant as before.

2. copied the fiber wavelength and paste in the frequency box i.e. equal to 1550 nm as the fiber.

3. The layout parameter kept constant.

4. the WDM mux and WDM demux modified with the no of channels equal to 4.

5. all the channel spacing and bandwidth kept constant.

please have a look at the modified circuit.

Regards,
Dhiman

[Ubaid Bhat]

Hello burhan num mina llah…

i agree with all responses above that you should unclick the option of reference frequency so that default value is central frequency.
you should also try other things suggested by the forum masters. Hope your problem gets solved.
with Regards.
ubaid bhat

[burhan num mina llah]

Hello dhiman kakati

Thanks for uploading your modified file .. I would check it as soon as i get access to the license in the working hours.. And would try to implement same in my project and see if it works for my case or not.. I would update you likewise and i believe if it has worked for you it should do the same in my case..

Regards

Burhan

[Dr. Dhiman Kakati]

Hello burhan num mina llah,
Hope you also get the same result as i have in the attached file, I just did very simple modification as in the previous reply of mine and you can also get further better result. I took the reference from “WDM Systems folder” available in the “OptiSystem 13 Samples” for making it dense wavelength division multiplexing you need to set wavelength separation lesser and look for better result and respective modification. In my attached file the frequency spacing is 200 GHz and got a better solution. You should try from your side and decreasing the spacing and look for results.

Regards,
Dhiman

[burhan num mina llah]

Hello Ubaid bhat

Thanks for your valuable suggestion but i did try it as it was suggested by aasif bashir dar as well.. But i got the same distorted eye diagram.. I would request you to take a look at the .osd file i have uploaded in the previous comment if you have optisystem 14 version.. Then you people would help me out in a better way.. Hope to see a response soon..

Regards

Burhan

[burhan num mina llah]

Hello Dhiman Kakati

Thank you very much for your help.. I would try to implement it and update you accordingly..

Regards

Burhan

[Dr. Dhiman Kakati]

Hi Burhan,
Hope this time your problem should solve.

Regards,
Dhiman

[burhan num mina llah]

Hello Dhiman Kakati

i simulated the design you have uploaded.. it has very fine results.. can u please tell me the exact name of the 32 channel system you have modified.. and i would try to implement same in regards to my project as soon as possible… thank you anyways for your help and concern… it would really help me out..

Regards

Burhan

[Rajguru M. Mohan]

Hi Burhan ma’m
You should check out the CW laser power as being suggested by Dhiman by increasing the laser power to few dbm.
You should Check for Wdm mux bandwidth , filter order if you are not using ideal mux.
You should also vary the channel spacing by varying the frequency of laser, because according to TIU-T, the standard channel spacing are for WDM system are 25 ghz, 50 ghz, 75 ghz and 100 ghz, 200 ghz, 1 thz .
Check the output at different ports in the design.

You could also Vary no. loops of fiber because for small laser power WDM system gives no results at very large transmission length.
Seeking your response.

Thanks and regards
Rajguru

[Duy Le Nguyen]

Hi Rajguru!
Can i ask one question? I’m studying about OFDM-WDM system so I’m making a project – 4QAM Direct detecter OFDM WDM with 16 channels. The results from 1st channel to 10th channel seem ok. But from 12-16th channel, the results aren’t good.
What parameter i should change?

Thanks and regards.

[Rajguru M. Mohan]

Hi Duy Le Nguyen,
Could you please upload the osd file or image of your design.
So, that i could understand it, then try to help you.

Seeking your response.

[Duy Le Nguyen]

Hi Rajguru!
Thank you so much for your reply. But I resolved that issue. I tried to decrease the channel spacing from 100 GHz to 50 GHz, so it’s ok. Now I’m trying to use 16-QAM in my system.
And can I have another question? At the beginning, i worked in OFDM modulation sample, and I tryied to increase bit rate from 10 Ghz to 30 GHz, then I modified some parameters but the result is so bad. If you worked on same problem, could you give me some hints?

I’m very appreciated for your help? I’m still a newbie.
I attached my osd file below.
Best regards.

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