DQPSK WDM

Hello Urvi Pathak,
Thank you for providing me with the attachment. I will try to resolve your issue. I need some more time.

Regards,
Dhiman

Hi Urvi pathak,
I am also not getting the expected output. rather I am getting an eye diagram as attached in the reply no. 33931. Still looking into the problem and once I get the solution I will upload the design file. without using WDM the system is giving very good result but when I implement the same transmitter and receiver in WDM the eye diagram is as in abouve component. Thanks for the patience.

Regards,
Dhiman

Hello Ranjeet Kumar,
If you provide with the papers pdf filed attached here this will be more beneficial to me as I dont have IEEE access ate present. Thanks in advance.

Regards,
Dhiman

Hello Urvi Pathak,

In my case the problem is with the demodulator, up to the demodulator everything is ok and as expected (Spectrum and signal power), but after the demodulator the constellation is also not coming (just few signal points are seen). I don’t thing so that there should be problem with the demodulator because without WDM everything is working fine. The problem may be at the WDM multiplexer and demultiplexer in the filter bandwidth, or at the transmitter laser frequency spacing. try changing these parameters.

Regards,
Dhiman

Hi Kevin Xiang,
I am not getting your point, Will you please elaborate. Why you have suggested polarization mode splitter, How it is going to help (except for twice the bit rate) we have not implemented polarization splitting technique here.

” we produce 405nm,532nm,635nm,650nm~1650nm splitter,WDM, such as 532/635nm PMWDM etc, which are used in OCT, QPSK ,EDFA, etc.” are you referring to practical implementation or practical design not a simulation platform..? looking forward for your kind response. Thanking you.

Regards,
Dhiman

I agree with Sanjeev Kumar that in my case also a single transmitter and receiver (i.e. without WDM) I am able to get a maximum Bit rate of 10 Gbps. Urvi You also should try to reduce the bit rate at each transmitter to a maximum of 10 Gbps.

Regards,
Dhiman

Hello Sahil Singh,
for viewing the link you need to have a research gate account. I am attaching herewith the words what I was suggested.

According to him,

1. in conventional DQPSK scheme, a delay of 1 symbol is required for direct detection1..

2. sample the waveform at 2.56 THz, with 256 samples in each of 128 symbols for a sequence length of 12.8 ns.  The symbol rate is 10 GBaud,
with 2 symbols/bit for an aggregate bit rate of 20 Gbit/s.

3. the symbol rate 5 GBaud with 64 symbols each of 200 ps period? In this case your demodulator MZ delay of 2/Bit rate is correct.

4. A 2.5 GHz pulse train would explain the zeros in the eye.

So these are the main points arose by Alan.

Regards,
Dhiman

You are most welcome Sahil,

Now I have managed to get a better output, my problem was mainly due to some common mistakes in layout parameters and bandwidth of the demultiplexer. I have attached here with the eye diagram and constellation, please have a look.
Alan Robinson’s suggestion was very much helpful in this case. anyways Thanks to all for discussing and look deep into Urvi’s problem. This is now gets solved.

Regards,
Dhiman