FTTH using OCDMA

[sulaiman]

Hello,
How is the encoding done in the examples FE-OCDMA-3Users and FE-OCDMA-7Users and how to increase the no. of users?
Thank you,

[Damian Marek]

If you have more users you only really need to have larger code words. Then in the physical SAC-OCDMA type system you would need more fiber bragg gratings.

[Heitor Galvao]

Good afternoon there are some sample file?

[sulaiman]

thanks Mr Damian but how is it done I need to know how is the system work

[Fady]

Could you please post a sample for larger no. of users (more than 7 users)? Thank you and happy new year!

[Damian Marek]

Hi all,

There is a sample project on this subject in the Access systems folder that I have also attached. The code word has a length of 8 and the coding is done using Hadamard code.

Regards

[Heitor Galvao]

Thank you

[Heitor Galvao]

Hi Damian this file in which version of optisystem?

[Damian Marek]

The version number is OptiSystem 13.0.1

[Heitor Galvao]

Ok

[rafik hisham]

Hey it’s a great work but i have some questions would you help me with it ? if i want to extend number of users in this system what should i do which codes i use? which range of wavelength and what about the Receiver decoder ?? thanks in advance

[Ravil]

very useful, thanks Damian!

[sulaiman]

Hi Damian,could you pleas give example 9uses
and how i can put the code in the FBG

[Damian Marek]

Hello,

Could you attach an article or paper with 9 users? From my quick look I didn’t find any with 9 users, so I am not exactly sure how to generate the code words.

Regards

[sulaiman]

Hi Damian,
How I can put the code words in FBG for FE-OCDMA-7-Users

[Damian Marek]

Hi Sulaiman,

Once you have the code words, that are generated first by the type of code you are using and the number of users, you can code each users spectral content by assigning each bit of the code word a wavelength. In our OptiSystem example, the range of wavelengths goes from [1549 1549.5 1550 1550.5 1551 1551.5 1552 1552.5] nm. You will notice 8 wavelengths for a code word of length 8.

Now assigning the rule that a bit value of 1 means the user’s signal will contain that wavelength spectral content, we can place four fiber bragg gratings to create stop pass filters for the undesired spectrum (bit values equal to 0). From Hadamard coding, there will always be 4 zeros in every code word.

I have attached a picture of the 7 users and their code words following Hadamard coding.

Regards

[sulaiman]

Hi Damian ,
Thanks a lot for answer but I need to know how I put the codeword0nFBG in the layout simulation and how i can used anther type of coding like Modified Quadratic Congruence (MQC) codes.

[Damian Marek]

Hi,

Maybe I am misinterpreting what you mean by put the codeword on FBG, but I think my earlier reply answered that. If you take a look at the example file that comes with OptiSystem “FE-OCDMA 7 Users.osd” you will see that the first user has codeword: 10101010 which means we need to remove the spectral content belonging to wavelength2, wavelength4, wavelength6 and wavelength8. Using a FBG centered at the undesired wavelength you can reflect only that wavelength, so after placing 4 in succession the four wavelengths can be removed.

I have attached some screenshots of the project to hopefully make it clearer.

I am not familiar with MQC, but I believe once you can find the codewords for the different users then the procedure of placing the FBG’s is the same. Let me know if anything is unexplained!

Regards

[Fady]

Could you please answer Sulimans question above? Many thanks

[sulaiman]

Thanks Damian
I try to make user 3 on in the examples FE-OCDMA-3Users but it remain off and the BER decrease could you pleas solve this problem

[Damian Marek]

In the White Light source you need to both Enable the component ins the Simulation tab and loss convert Noise Bins in the Noise tab.

[sulaiman]

Thanks Damian
Could you please give attachment

[Damian Marek]

Of course! Note this is a file from OptiSystem 13, so you will need the most recent version to run it.

[sulaiman]

Thanks Damian
could you pleas give attachment to make user 3 on and give good BER for 3 user in FE-OCDMA-3-Users.

[Damian Marek]

Please find attached!

[sulaiman]

HI Damian
could you pleas give attachment to make FE-OCDMA-3-Users for FE-5users

[Damian Marek]

Hi Sulaiman,

The exact coding choice you want to use will change the gratings used, for example the Hadamard or Walsh code which is what I am most familiar with has codewords of length 2^k, so 4, 8 etc. The number of users that it is optimized for is one less than the codeword length, so 3 and 7. I don’t believe a 5 User FE-OCDMA Hadamard is a common system, but you could make it by simply removing two users from our 7 User example we have.

If you have a different code word scheme just let me know the code words and I can make it quite simply.

Regards

[Fady]

By the way what is the codes used for the 3 users example? Thanks

[Damian Marek]

It uses Hadamard code.

[sulaiman]

HI Damian
what is type of code used in FE-OCDMA-3-UsersON

[Liju Mohan]

Hi.. I have tried to create a 3 user Sac-OCDMA system using the MQC coding scheme and have accordingly created the FBGs based on the codes for the encoding and decoding sections. However, i still happen to be experiencing some issues. When any user is turned ON individually, i get a clear output, as in acceptable BER values. But if i were to turn ON all the 3 users simultaneously, i got not output what-so-ever. Any suggestion as to why that might be?

[sulaiman]

Hi Damian
could you pleas give attachment to solve the problem in FE-OCDMA-7Users. when the simulation run the results are good for usess1,3,4,5, and7 but users2 and user6 the BER are bad i need to decrees BER for use2and use6

[Damian Marek]

Hello Sulaiman,

I can troubleshoot your project file if you attach it to your post.

Regards

[sulaiman]

my project is FE-OCDMA-7-Users.osd its a sample in the V13

[Damian Marek]

Just running the default sample file I get reasonable BERs for all users. Since the sequence length is only 2048 there is some fluctuation of the BER from simulation to simulation. Perhaps this is the problem for you. Try increasing the sequence length until you get a more reliable BER result.

[sulaiman]

Thanks Damian, I have increased the sequence length but there was no improvement. When increasing the bit rate from 200 Mbps to 400 Mbps or more I got bad results . Also I got bad results when increasing the input power. Could you please help me with that. Many thanks

[Damian Marek]

Hi Sulaiman,

I know you are working from the sample but do you mind attaching your project file and clarifying what the bad results are? The BERs are too high?

Regards

[sulaiman]

Thanks Daiman, Here is my project attached (BER versus Data rate). You can see the BER deteriorates by increasing the data rate. How can I get higher data rates? Best regards

[sulaiman]

Thanks Daiman, Here is my project attached (BER versus Data rate). You can see the BER deteriorates by increasing the data rate. How can I get higher data rates? Best regards.

[sulaiman]

Hi Damian, could you pleas How can I get higher data rates?in up attachment

[Waqas Ahmed Imtiaz]

Hello,
I am simulating SAC-OCMDA system using my designed code. However I am having trouble with the concept of putting FBGs for “0” in code. Because my code contain six zeros when the number of subscribers is 4, and as I increase the number of subscribers, 0’s also increase.

My question is do we need to represent every 0 with an FBG, or we just have to represent the one’s that are close to 1 in the code.

Plus does the trailing bit matters because it also represent 1 for that matter?

[Waqas Ahmed Imtiaz]

Code and output sequence of User 4 for my question

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