Generation of RZ-DQPSK modulation for different duty cycles

[siva rama krishna]

Hi,

How to generate different duty cycles(40%,50%,60% etc) of RZ for DQPSK Modulation?
If i used example DQPSK Signal 33 percent.osd file,which parameter has to be changed to get different duty cycles of RZ(DQPSK modulation)?
Otherwise is there any another way to get different duty cycles(like directy using RZ driver instead of extra MZM modulator)?

How can set the LiNb MZ Modulator settings(like voltage values) w.r.t DQPSK modulation?

Please help me with complete details.

[siva rama krishna]

To generate RZ signal extra MZM modulator and sine wave generator is used in many examples and papers.
Why can’t use directly RZ pulse generator instead of extra MZM modulator?

Please provide any explanation for the cause.

Thanks
Siva Rama Krishna

[Damian Marek]

A simple way could be to use an Optical Amplitude modulator (same folder as the mach zehnder modulator’s) and modulate with a Sine Pulse generator. I’m not sure about making different duty cycles with MZM’s directly. Do you have an article that I could look at?

Regards

[siva rama krishna]

Please reply

[siva rama krishna]

Please find the attached paper

Attachments:

1. RZDQPSKmain.pdf

[Damian Marek]

Attached is a direction you could go to get these different duty cycles. I am not sure what type of pulse they used in the paper (rectangular?) but I used a higher order Gaussian to emulate a LiNBO3 modulator output. You can change the width of the gaussian pulse generator to get different duty cycles.

Cheers

Attachments:

1. HighOrderGaussianPulseCarving.osd

[siva rama krishna]

Hi Damian,
Thank you for reply.And Your solution gives the way generating different duty cycles for RZ.That’s clear.
But my question is why can’t use RZ pulse generator(paremeter: Duty cycle) to get RZ with different dury cycles.Why can’t use RZ pulse generator instead of NRZ pulse geneartor in DQPSK Signal 33 percent.osd?
If possible with RZ pulse generator,then we can use directly “duty cycle” parameter of RZ pulse generator.

Please provide your assistance.
Thanks in Advance
Siva Rama Krishna

[Damian Marek]

Yes absolutely. Simply replace the Gaussian pulse generator with an RZ pule generator in my project and it will work.

[Ibn Aziz]

Hi Damian Marek

thanks for ur kind response and sharing file of high order gusian pulse carving.

But dear i need optical pulses at the output through any mean by using CW lase source at the input.

For that i need ur help and the paper about which i ref u is using the same idea in which he used CW laser+RF signal and modulat it by using 4 MZM modulators.

I did the same i got pico secnd pulses.

But problem is that i need

Time period of optical pulses = 7.8125 nsec
pulse width of optical pulses = 1 nsec

which i am not getting.

if u know any way for getting such pulse plz share.

i am also attaching figure of such pulse.

regards

Attachments:

1. 

   1.jpg
   

[Dr. Dhiman Kakati]

I need to generate a DQPSK signal at 10Gbps bitrate, please provide me with steps.

[alistu]

Please see if my answer in your DQPSK topic helps.

[gaganpreet Kaur]

Hi Damian pls it would be gr8 help if you could send me the snapshot of highordergaussianpulsecarving.osd design file. actually i have optisystem 7.0 and unable to open the file and i need the modulation format for high fat rate transmission.
Thanks in advance , pls help
Regards

[alistu]

Hi Gaganpreet,

I have attached a snapshot of the system Damian has attached at your request. Since it’s the weekend, I figured you might be waiting for a while for it otherwise.

Regards

Attachments:

1. 

   gaussian.jpg
   

[gaganpreet Kaur]

Thank u so much alistu i was seriously waiting for it coz i need to understand difference in output BER with NRZ, RZ and DP-QPSK modulation at 100 Gbps. thanks again

[Ashu verma]

Gagan screen shot attached by alistu is from latest version.There is dp Qpsk transmitter and i dont think exact transmitter is there in optisystem 7.

[alistu]

You’re welcome Gaganpreet. I am glad it saved you some time.

The screenshot I have attached at Gaganpreet’s request belongs to the highordergaussianpulsecarving.osd file Damian has uploaded in this page, which is attached on reply #14888.

Cheers!

[gaganpreet Kaur]

Sam we are using QPSK to get DP-QPSK so its there in optisystem 7.0 and was gr8 help to me

[Ravil]

Hello Gaganpreet,
I am not sure that you noticed it but I just want to mention to you that if you have modeled you QPSK scheme already (as you said in the previous comment) you can convert it to DP-QPSK by adding polarization controller. When I was working on it, I used example https://optiwave.com/applications/100-gbps-dp-qpsk-system-with-digital-signal-processing/ and its references.

[alistu]

Hi Gaganpreet, I think you can easily find out if the component is there in Optisystem v.7. If the aforementioned block exists in version 7, you can find it in transmission library (or any other name it has in version 7), where other coding schemes (such as QAM and PSK) are there.

[gaganpreet Kaur]

hi alsitu we have OQpsk in optisystem 7.0 and not QPSK. can OQPSK be used to generate DP-QPSK.

[alistu]

Can you please tell me if the PSK coding component is there in Optisystem v.7? If it is available, then by choosing the “bits per symbol” parameter as 2, you can have QPSK. Other than that, QPSK and 4-QAM are the same. So by choosing QAM modulator and changing “bits per symbol” to 2, you can have QPSK coder/decoder.

[gaganpreet Kaur]

Thank you so much alsitu. if i need to use DP-QPSK for a wdm system do i need to apply the modulation described in this forum to each channel separately where we have a CW laser as input source as input at one particular wavelength.

[alistu]

You’re welcome Gaganpreet. Yes, in a WDM system where the channels are seperated from one another by frequency(wavelength), you would apply the coding scheme used to every frequency channel. You may have used a separate CW laser for each channel, or the WDM CW laser as source to all channels.

[gaganpreet Kaur]

PSK coding component is available in optisystem 7.0 and by default number of bits per symbol is 2 only. hope it works. Thanks

[Ashu verma]

Since Qpsk is not in optisystem v7 we need to make it by own using psk .But some time ago when i was using same versuon v 7 ,i tried to make qpsk and fortunately completed it .But when i started analyzing constellatin by adjusting electrical amplifier values i got saturated results.For example i increased thre distance from 10 km to 1000 km further 10000 km but results on constellation were same .Back to back system i got with sane as with transmission line.I would realy like to help you and discuss it here because if qpsk works good in 7 then it solves many problems for users.unfortunately setup that i have made ,misplaced otherwise it would help .Gagan try it by searching qpsk transmitter on google then images ,there are some optiwave screen shots of Qpsk,try to make it and we will discuss it.
Thank you

[gaganpreet Kaur]

is there any way that i make DP-QPSK and use this design as component in next design because the screen shot i got surely gives Dp_QPSK signal but ti use it for WDM design even for small channels numebr it becomes cumbersome to use it at each wavelength modulation

[Ashu verma]

Sorry i Didnt get what actually you are trying to say?Are you refereeing to single dp Qpsk transmitter as in screen shot?

[gaganpreet Kaur]

yes Sam, i am refering to design of DP_qpsk suggested on this forum which uses 4-DPSK precoder. i designed a single laser source modulated by DPQPSK as .osd now is it possible that i use this .osd project/file as component in another optisystem design.i hope i could make it clear now

[Abhishek Shrama]

Hi! Gaganpreet ,Could you please attach the DP-QPSK transmitter.According to my knowledge i think in v7 there is no DP-QPSK transmitter.But i am not sure because i am no=t using old version and it is there in latest version.I am sure about DQPSK.Now have you made DPQPSK from DQPSK? if yes then i am curious to check the system file.Kindly attach it.Since as you said above, you successfully realized DPQPSK then there is no issue to use it in other optisystem file or in new layout.
Thank you

[gaganpreet Kaur]

Hi abhishek u r right optisystem 7 has no Dp_Qpsk transmitter. i found it on this post by alsitu . u may check previous post on this topic there is a screen shot sent for generating DP_QPSK

[alistu]

Hi Gaganpreet,

I don’t know if you are referring to my reply #24637 in this topic or if you are referring to any other file, but in the screenshot I have attached (which belongs to the file attached by Damian in his post preceding mine) there is no no Dual-Polarization component as I notice. Am I right?

Regards

[Abhishek Shrama]

Hi Alistu,gagan confused me alot.Thanks for the confirmation and she is continuously referring to the screen shot of DP-QPSK attached by you.But i have read this discussion many times and couldnt get any of the component.However the screen shot is there which you have uploaded but consisting of no DP-QPSK .

[Abhishek Shrama]

Hi! Gagan,I coudn’t found any screenshot.Please mention the reply no., so that i can study it with great care.Thank you

[gaganpreet Kaur]

Hi abhishek sorry for confusing u actually i wanted to refer to post no. of alsitu #24565 in response to DQPSK by dhiman in which alsitu suggested to generate DQPSK using DPSK (which is there in optisystem 7.0). Yes screenshot i referred to suggests use of RZ insead of gaussian to generate RZ-DQPSK. i hope i am able to make it clear now.

[gaganpreet Kaur]

Apart from that i found another snapshot don’t remember from whom and to which question it refers . the attached snapshot guided me for DP-QPSK generation. i hope it will help u

Attachments:

1. 

   dpqpsk.jpg
   

[Abhishek Shrama]

Thank you Gaganpreet,Could you please attach the .osd file if you made this? It it hard for me to set the values of MZM and since you are working on it ,so it would be better if you attach file.
Thank you

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