Compensation techniques

[siva rama krishna]

Hi,
1) I ran Dispersion compensation pre post symmetrical.osd for 10 Gbps
2) I noted the Q values for each iteration( CW power changes) for 3 compensation schemes.
3) After replaced NRZ with RZ electrical modulator.
4) Again noted Q values for each iteration( CW power changes)for 3 compensation schemes.
5) Observation: My observation is found that Q for RZ values is less than that of NRZ. But in general RZ is superior than NRZ in modulations.
6) In this case is it is failing.
7) Please any one guide me whether my analysis is correct or not.Please give suggestions for this one.This is important project for me.

Thanks
Siva Rama Krishna

[Damian Marek]

Hi Siva,

I have moved this to the System forum. Posting in the Knowledge section is reserved for our moderators, sorry for the confusion. However, feel free to reply to a post in the Knowledge section if you want a point clarified!

[Damian Marek]

Please find the attached files.

For the “Dispersion compensation pre post symmetrical.osd” example, when we compare the performance of NRZ and RZ, we normally set the input power of the fiber (launch power) to be the same. NRZ and RZ signals have different modulation efficiencies. Therefore, the modulated signals has different powers. My suggestion is adding an optical amplifier after the modulator and before the loop control, and set the power for both cases to be the same, as shown in the attached osd files. For the same launch power, RZ has a better performance than NRZ.

By the way RZ signal has a wider bandwidth than NRZ signal, therefore the bandwidth of the filter should be different for different cases.

Attachments:

1. Dispersion_Comparison_NRZ_RZ.zip

[siva rama krishna]

When i tried to open the your file the following error is coming in version 10.
“Failed to load document from storage”

I think problem with version conversion. How can i open version 12 files in version 10 ?

Please reply.

[Tech Support]

Siva,

Our software is backward compatible, however, it is not forward compatible – meaning that you can only open files from your current version or older.

To run v12 files, you would need to upgrade your license or download an evaluation: https://optiwave.com/evaluation-license-request-form/

[alistu]

So just by using a newer version for one time and saving the file, it can’t be loaded by the older version even though the file has been created in the older version in the first place??
That’s what I realized has happened to me right now… Lost all the work I’ve been doing for one month (while using the trial)
A warning is really necessary the first time the software runs.

[siva rama krishna]

Thanks for your reply. I got that RZ is better than NRZ.
My analysis: Replaced DCF part with Ideal dispersion compensation FBG in post compensation and found that FBG is giving better than DCF. But in in paper found that DCF compensation technique is better than FBG.
I am attaching the paper.(line is highlighted in yellow color)
Please provide your thoughts.

[siva rama krishna]

Please reply for #10670.

Thanks

[Damian Marek]

Hi Siva,

I can’t see your attachment file. Could you try attaching it again and see if using a .zip file will work?

[siva rama krishna]

The attachment is done.
One more thing.The following error is coming when i tried to open your file “Failed to load document from storage”.
I am using OptiSystem 12 and Windows 7.
Please send the version 12 file if not possible provide the image with circuit diagram and important parameter values.

Attachments:

1. An-Improved-Methodology-for-Dispersion-Compensation-and.pdf

[Damian Marek]

Here are diagrams of the the two networks. They look very similar to the diagrams in your attached paper. It is hard for me to say why they are getting better dispersion compensation with the compensating fiber than the fiber bragg grating. I don’t see a design using gratings.

On the other hand, it is probably because you are using the Ideal Dispersion Compensation on FBG component, which is probably not the model the referenced authors used in their FBG design. If you have access, look at the referenced paper given below, I believe it is the paper the authors of your paper have referenced. They mention they used an original apodization technique. Once you find out what it is you can try to model it with the Fiber Bragg Grating component. For this component, you can set the “Apodization function” to user defined to get a better match.

Sa, L.M.; Nogueira, R.; Andre, P., “Simplified technique for the design of multichannel dispersion compensation FBG,” EUROCON – International Conference on Computer as a Tool (EUROCON), 2011 IEEE , vol., no., pp.1,4, 27-29 April 2011

Attachments:

1. 

   NRZ.jpg
   

2. 

   RZ.jpg
   

[Dr. Hamza M. R. Al-Khafaji]

Hi Siva, what you say it in your first post is correct. NRZ is better than RZ for 10 Gbps rate or below. RZ is superior at higher bit rates. Replacing DCF by Ideal dispersion compensation FBG is not the solution. Normally, DCF compensation technique is better than FBG.

[Ravil]

Hi Siva,

In general, RZ format is preferable for bit rates higher than 10 Gb/s due to pulse broadening issues. However, since you are working with the bit rate of 10 Gb/s and using appropriate dispersion compensation techniques, NRZ bit rate will be more beneficial due to increasing pulse energy (which is higher with the respect to noise in this case!). According to my experience with the dispersion compensation, the choice of particular compensation technique depends on your particular scheme design…

[Author]

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