- This topic has 16 replies, 6 voices, and was last updated 10 years, 6 months ago by
Philip Weetman.
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May 13, 2014 at 10:09 pm #11501
Roman Ibragimov
ParticipantHello everyone. So last month I tested OptySystem 12.2. But I had some problem with total result simulation.
For example, i downloaded examples here https://optiwave.com/resources/downloads/optisystem-hot-topics/ and started simulation.
But I had BER=0.5. It’s impossible. After that, i opened new project and made simulation with same parameters of simulation. again i had BER=0.5. But maybe I was wrong. So, attached screenshot with my project. -
May 14, 2014 at 4:29 pm #11523
Abdallah Ismail
ParticipantDear Roman,
I think one of the two bits in QPSK is recived in error all the time,so i suggest to follow the design and test each point from the start to the end.-
May 15, 2014 at 12:37 am #11525Participant
Dear Ismail, you right!
Problem was in PSK Sequence Decoder.
Two input ports has bitrate 5Gbit/s respectively, but output port had bitrate 1Gbit/s.
I dont khow how fix this mistake. PSK decoder has 4 parameters (2 parameters disabled). And we have only 2 main parameters in this block – bit per symbol (2 bits for QPSK) and Phase offset (45 deg).-
May 15, 2014 at 1:11 am #11526Participant
Oh, please excuse me) I was wrong)
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May 15, 2014 at 1:33 am #11527Participant
If you check scheme from samples you will see that BER=0. it’s strange for any optical system. we have BER approximately 10^-20 – 10^-30, but ber=0 it’s not true result
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May 16, 2014 at 11:58 am #11650
Philip Weetman
ParticipantHi Roman,
The BER from the BER Analyzer is calculated in a statistical manner (which it has to be for such small sequence lengths) from the size of the eye opening and the standard deviation of the pulses from the ideal positions. In your case, you have M-ary threshold detectors and psk decoders before the BER analyzer and thus the pulses are now at their ideal positions so there are no standard deviations and therefore zero BER.
So you should either modify your system so that the signal is sent to the BER Analyzer before being pinned at the thresholds or look at our BER test set, this component doesn’t estimate the BER, but does a straight counting, comparing initial signal to final signal. The drawback of the counting method of course is that it may take a very long sequence to actually see a bit error.
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May 19, 2014 at 1:20 am #11704Participant
So, You suggest me using Ber test set and connect outport and inputport with help this block. You can see that I attached screen with ber test set and standard QPSK TRansmitter and Receiver. In this case I have BER=0,5. where i was wrong?
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May 17, 2014 at 8:47 pm #11701
Luis Acevedo
ParticipantGreat, evaluation examples. I love it
I do not have Optisystem . oh 🙂
Any ideas how to get an extended trial?
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May 20, 2014 at 7:42 am #11720
Bryan TipperParticipantTo request an extended trial of any software, simply fill out the following form: https://optiwave.com/full-evaluation-extension-request-form/
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May 20, 2014 at 8:36 am #11721Participant
Thanks a lot Bryan
Which product do i need for a Michelson interferometer with fiber optics?
optiSystem or/and optiBPM
Cheers
Luis
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May 20, 2014 at 9:46 am #11724
Damian Marek
ParticipantHi Luis,
Do you want to investigate the total power transmitted or see details of the interference pattern?
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May 20, 2014 at 10:27 am #11728Participant
Hello Damian
I would like to analyse the interfence pattern.
Luis
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May 20, 2014 at 4:15 pm #11738Participant
OptiSystem or OptiSPICE could calculate the power output with respect to changing the delay of two signals, but it would not be able to determine the spatial interference patterns. You may want to start a new Topic with this as your question. It might be possible in OptiFDTD or OptiBPM.
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May 20, 2014 at 10:29 am #11729Participant
Interference pattern of an image 🙂
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May 20, 2014 at 5:13 pm #11739Participant
Hi Roman,
I will have to think about it. For now, would you like to try your system using our DSP and Decision component? I attach a diagram showing this.
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May 21, 2014 at 6:26 am #11742Participant
Hi Philip,
It’s method interesting. But i have some questions. Firstly, did you have leading zeros and trailing zeros in BER test set?
Secondly, why did you disable “Dispersion compensation” in block DSP for QPSK? what is difference between block “Decision” and “M-ary threshold detector”?
And last question, in my opinion, it’s curiously for optical system BER=0. There is ber within the limits of 10^-10 ….10^-50.
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May 21, 2014 at 12:07 pm #11747Participant
Hi Roman,
In this case I had no leading or trailing zeros.
In addition to the threshold detection of the M-ary, the “Decision” component performs functions such as: Constellation rotation, Alignment and Polarization rotation … check out the help section for this component, it has lots of good information.
I didn’t bother with “Dispersion compensation” because your fiber was only 1km in length. You can add it if you wish.
It’s not surprising that BER = 0. If your system has low enough noise (and a good enough DSP) that you have a BER like 10^-10, that means for every 10^10 bits, you will encounter one error. In this system, there were only 128 bits sent, so it is highly unlikely that you would actually encounter the bit error.
To measure BER, the straight counting like the BER test set will be the most accurate method, but for very low BER systems, your sequence length will need to be impractically large. If you don’t want such a large sequence length, then you have to use estimation techniques based on statistics (like our BER analyzer).
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