FTTH using OCDMA

Good afternoon there are some sample file?

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

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

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

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

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.

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

Please find attached!

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

It uses Hadamard code.

Hello Sulaiman,

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

Regards

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.