Design of a Niquist-filtered 100 Gbps PM-DQPSK (DP-DQPSK) transmitter

[xiaoyong chenParticipant]

Hello everyone,

I have a problem in design of a Niquist-filtered 100 Gbps PM-DQPSK transmitter. I tried to use the optical raised-cosine filter to shape pulse of the generated PM-DQPSK signal, but it failed. I also tried to use the electrical raised-cosine filter to shape the driven NRZ signal, then to generate narrowband (25GHz) optical PM-DQPSK signal, but it failed either. Is there someone can tell me how to design a Niquist-filtered 100 Gbps PM-DQPSK transmitter? Thank you very much!

Best regards,

[Damian MarekParticipant]

Hello,

I fixed up your project and got it working there was problems with the transmitter!

Be careful when copying components from example files into a new project, because sometimes they will be referencing parameters that might not exist in your layout. For example I had to add a layout parameter called “rolloff” to your project so that the M-ARY Raised Cosine Pulse Generator would give reasonable results.

Moreover, careful consideration of the biasing and driving of MZM’s is needed. I added an electrical gain and bias to the inputs so I could copy close values from the example file. Then I played with the gain until I got good results. It is also possible to modify the gain and bias inside the parameters of the MZM, but I prefer explicitly setting the gain and bias before and only changing the Vpi of the MZM.

Regards

Attachments:

1. Nyquist-filtered-QPSK-and-normal-QPSK-DMedit.osd

+1

[xiaoyong chenParticipant]

Dear Damian,

Thank you very much for your help. Now the program works and I have successfully changed the bit-rate to 100 Gbps.

Thank you!

[xiaoyong chenParticipant]

Hi Damian,

Sorry for bothering you again. I have another question about Nyquist-filtered QPSK signal. In the last file you attached to me the Q-factor of the Nyquist-filtered QPSK is only 7, is it possible to improve the Q-factor to more than 10? Thank you!

Best regards,
Chen

[xiaoyong chenParticipant]

Dear Damian,

Thank you very much for your help. Now the program works and I have successfully changed the bit-rate to 100 Gbps.

Thank you!