problems faced in OTDV

[aasif bashir dar]

hi all,
OTDV——> optical time domain visualizer

in my system design i require to view the optical signal pulses at various positions in the transmission link..the positions
are….
1}after the MZM
2}after the fiber of 100kms
3} after the dispersion compensation unit…
4} after amplification.

but there are no. of bits bits missing in the initial stage or time

what to do?

with regards

[aasif bashir dar]

hi all,

i have now got the access to the software… i will post the pics of the regions 1, 2, 3 here with names of screen shot as per the position
hope you all got my query…. replies with be appreciated if related to my problem.
here are pics

with regards

[aasif bashir dar]

sory i missed the pics, here are these…

Attachments:

1. 

   1.png
   

2. 

   2.png
   

3. 

   3.png
   

[umer syed]

hi aasif bashir dar,

yeah looks like the the initial some bits are skiped in the in the 2.. and 3… picture… i think it is valid question…

but in my view it may be due to the delay of the components as the single tramnsmission takes place along the channel…

with regards

[aasif bashir dar]

hi umar syed thanks for the reply..

i my self belived at first that this might be due the delay of the of the individual components …but i am not sure…

if it is like that … how can i get the the bits which i lost at first in optical time domain visulualizer….

i want the same bits at the begining of of each of the otDV…

looking ahead for sol… i am my self investigating for solution… when i would have i will also post here

with regards

[Dr. Dhiman Kakati]

Hi Aasif I am not clear about type of signal you are using at the input in electrical domain, it seems you are using non-polar rectangular pulse as from the output of the modulator, can not be sure. Please upload the design file if possible. Thanking you.

Regards,
Dhiman

[Atul Sharma]

Hello Aasif Bashir Dar. Good Evening Greetings from my side.

I checked the images you have shared. One thing stuck my mind about the waveforms displayed in the images that it may be because of either the dispersion down the feeder fiber link or the attenuation caused along the fiber channel. The third snapshot you have shared is very much distorted and it gives me an impression that it is because of the attenuation factor that your symbols are lost. Also check the power levels it goes down from 1m to 20 u.

Regards
Atul Sharma

[SAHIL SINGH]

Hi Aasif

As rightly mentioned by Dhiman Kakati i am also unable to figure the type of signal you are using at the input in electrical domain….Please try to upload the design file if possible. Thanking you.

Regards
Sahil Singh

[aasif bashir dar]

hi dhimen and others…
i am using the non return to zero modulation format for my design… the fiber has the dispersion of the 17ps/km/nm and dispersion slope of- 0.175 ps/km^2 nm…MZM modulator is used at the transmitter end and CW laser is used for optical input.

i am very disturbed with the visualizer problem…i am looking for the solution…hope i will get it soon.

with regards

[Dr. Dhiman Kakati]

Hi Aasif,
now alittelbit clear, I think you are using the MZM in ON-OFF keyoing mode (depending on the bias voltage inside the modulator) as seen from the output. Yes i agree you are using NRZ pulse generator, are you using any modulation scheme… Which modulation Scheme you are using..?

Regads,
Dhiman

[Atul Sharma]

Hello Aasif bashir dar. Greetings.

Thanks for sharing your system parameters. But to my understanding this problem should be in no way related to modulation or any such a factor. I think it is the disturbance in your system due which your signal is getting attenuated to this very level and as a result of which you are not getting the required bits. Try using a higher order filter like of the order of 5 or so and check for the results again. I hope that may work.

Regards
Atul Sharma

[aasif bashir dar]

hi dhimen kakati,
thanks for the reply

i am using simple on-off keying

with regards

[ZULKARNAIN]

hi aasif bashir dar..
i also think that it may be because of dispersion down the line or attenuation alomg the fiber.
well i am not sure about your bit sequence whether it is random or user defined.If it is random then you can try with a user defined bit sequence. Hope it may resolve your problem.
with regards.

[aasif bashir dar]

hi zulkarnain,

thanks for the reply…
i beleive that it is not becoz of the fiber responses to optical pulses like you said dispersion, attenuation,or noinlinearity…..
further more you have provide an ides of using user defined bit sequence instead of the random bit sequence gennerator…i hope it may work i will try it soon and will you know.

with regards

[FAYIQA NAQSHBANDI]

HELLO AASIF BASHIR..

I guess this problem you had faced previously too.. And now i see the snapshots of the signals after three components you had mentioned..
To some extent i think ATUL Sharma maybe right in saying that this problem is related to the disturbance in your system due which your signal is getting attenuated to this very level and as a result of which you are not getting the required bits… he maybe right here..you should try using a higher order filter like of the order of 5 or so and check for the results again. I hope that may work.

Thanks & regards

[aasif bashir dar]

hi zulkarnain,

greetings…cheers

it worked for me… i now used user defined sequence 0010111011 and bit are not missing…but i try many sequences until it worked for me.

thank you very much for you ideas..
with regards

[ZULKARNAIN]

hi aasif bashir dar..
You are always welcome sir.i am very glad to know that it worked for you.
with regards

[Aabid Baba]

Hello Aasif,
So what was the exact problem you were facing and how did you overcome it. It will be worth mentioning if you are okay with it. you had recently posted about it and sorry couldn’t join the discussion but i would like to know what was the problem and the way you solved it. It may be helpful in future. I hope you won’t mind in sharing that.

Regards

[aasif bashir dar]

hi aabid baba

both problem and solution are well explained in above comments… you just go through them

problem was
OTDV——> optical time domain visualizer

in my system design i require to view the optical signal pulses at various positions in the transmission link OTDV——> optical time domain visualizer..the positions
are….
1}after the MZM 2}after the fiber of 100kms 3} after DCF and amplification.

but there are no. of bits bits missing in the initial stage or time
solution

was suggested by the zulkarnain … and it worked for me… to use user defined bit sequence instead of the random bit sequence gennerator
with regards

[SAHIL SINGH]

Hi aasif Bashir,

Thanks for the detailed explantion of the solution to your mentioned problem… I am also glad to know that your query has been solved…

Regards
Sahil Singh

[Aabid Baba]

Hello Aasif,
I did not go through the all comments but yeah i could see now what the main problem was and also the given solution. It may be helpful in future in one or the other way.

@zulkarnain well done.

Regards

[aasif bashir dar]

yeah thanks all for this discussion ,,as it provided some sort of solution to me

[Aabid Baba]

welcome Aasif.

[SAHIL SINGH]

Hi aasif bashir,

You are welcome and I am glad to know that you got some sort of the solution on the forum to your query… Also i want to correct you for one thing here that please use Mr Sahil instead of Dr Sahil… I hope it was unintentional..

Regards
Sahil Singh

[Author]

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