OWC QPSK Design

[Saurabh Sharma]

I am trying to design a 6 channel Optical wireless communication system using the QPSK modulation technique. The bit rate used in my design is about 20 Gbps for an optical wireless link up to 5000Km using OWC component. The problem is that after simulating each time we get BER=1, which is not desired so please help me out.

[Dr Rk Sethi]

you must start with minimum distance ( may be 0 Km), then check the result. BER = 1 means 100 % error.
Logically, the distance of 5000 Km is not possible for optical wireless link.

[Saurabh Sharma]

Thanks for the reply, but we have simulated the same design with acceptable BER using the NRZ modulation scheme with the same Optical wireless link, we are trying to use some advanced modulation technique.

[Dr Rk Sethi]

Saurabh Sharma Hi,
Welcome.
Can you attach the snapshot of both the scheme. what value of BER you are getting for NRZ scheme.

[Abhishek Shrama]

Hi shaurab
you can make a system with this much of link length.We used to take link length in thousand Km in case of satellite transmission.As there are many research paper in which distance of 40000+ has been studied.I can give you a link of the papers if needed.

[Dr Rk Sethi]

Abhishek Hi!
Please mail me the link of the papers, please.

Regards

Sethi Rk
drsethirk@gmail.com

[Damian Marek]

Hello,

I found the signal to be quite noisy and the detected constellation was very distorted. After disabling the free space component I got a much better constellation. I think your main confusion is coming from the BER Analyzer though. This is a common misuse of the component and you are better off using the BER Test Set.

LTE signal OFDM (64QAM)

Recently I explained why the BER Analyzer is not suitable for advanced modulation formats, the same applies to QPSK.

Regards

[Abhishek Shrama]

Here’s the link:
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6400458&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6400458

[Abhishek Shrama]

Hey Damain!!
In the link above paper shows eye diagram of Signal also and it is very fine.
I tried to simulate the same system but eye diagram appeared to be as in attached file. is my eye diagram correct? or what changes i do need to do to make it appear as one in paper?
and also my results are almost saturated. what is the reason behind it? even if i make major changes to the system very minor changes in q factor and BER are noticed.
and I also have a doubt about using OWC system with WDM. Is it really logical to make IsOWC WDm System as designed in a number of papers.

[Saurabh Sharma]

Damian Thanks to you for assistance

I tried using BER Test set as you said in the same design, but not able to utilize the BER Test set appropriately. If you can send me the same design with BER test set. Or isn’t possible to get the acceptable results without using BER test set. I seek after your assistance.

[Damian Marek]

Hey,

I added a BER Test set to one of the transmitters and got a BER of around 0.07, which is not spectacular but I am sure you could improve that with some design effort.

Regards

[Saurabh Sharma]

Thanks Damian

But it gave the error message when attempted to open your attached design file. I’m utilizing Optisystem 13.0.1.

Regards

[Dr Rk Sethi]

Saurabh Sharma Hi,
Please copy files to the desktop, and try to reload.
I hope it will be loaded.
Regards.

[Saurabh Sharma]

Hello RK Sethi,

I have tried to open the file from different locations, but every time it gave the same message as I mentioned earlier.

Regards

[Dr Rk Sethi]

Saurabh Sharma Hi,
I think problem is with version in-compatibility.
When one tried to open the file in different version following error is coming:
“Failed to load document from storage”
To run your files, you need to upgrade your license by downloading an evaluation: https://optiwave.com/evaluation-license-request-form/

[Abhishek Shrama]

Yes i am agree with RK Sethi,i also faced this type of problem some times ago.you can re- install the software,because same happened to me and after re-installing file,it start working properly.sometimes if you use optisystem 13 (32-bit) file in optisystem13 (64-bi) or vise versa then it may show this type of error.

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