DSP block

[Dr. Dhiman Kakati]

Hi all, in the DSP component, there are so many parameters that we have to set such as Polarization Type, Enable DC Blocking, Enable, Normalization, Enable Low Pass Filter, Enable Resampling, Enable QI Compensation
Enable Dispersion Compensation
Enable Nonlinear Compensation
Enable Timing Recovery
Enable Adaptive Equalizer
Enable Frequency Offset Estimation
Enable Carrier Phase Estimation
where so many algorithm are used so far as i have studied,
but the explanations I have found are not enough.
I want to know why all of the above are required such as DC blocking, normalization etc. how they are going to improve the detection process. Thanks in advance.

Regards

[alistu]

Hi Dhiman,

Not all of the above steps are required and necessary for correct signal detection, but they might just help with better detection sometimes. And their names somehow imply how they improve signal detection. Can you please name a few so that we would specifically discuss their function?

Regards

[Dr. Dhiman Kakati]

Hi Alistu, let us consider the Enable DC Blocking, Enable Resampling, Enable QI Compensation how these features of DSP going to help.

Thanks.

Regards

[alistu]

Hi Dhiman,

DC block, as its name implies, is used to block the DC signal that may be flowing into the main signal. In optical comminications, DC blocking can be used to suppress beat noise or for other purposes that lead to better SNR at the receiver. You can refer to the below paper where it has been used for such a purpose, for example:

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4216371&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F2220%2F4216340%2F04216371.pdf%3Farnumber%3D4216371

IQ compensation is used for IQ imbalance in the system, which might occur due to some mismatch in the way in-phase signal and quadrature signal are formed separately (the Q channel has to have an exact 90 degree delay,. Otherwise there is a mismatch). There are also many papers on “IQ imbalance compensation”, but I suggest first you visit wikipedia to know more about the concept if you are interested:

https://en.wikipedia.org/wiki/IQ_imbalance

Unfortunately, I don’t know about resampling, which may be upsampling and/or downsampling. I hope the component help section provides more information on each of these in the future versions.

Regards

[Dr. Dhiman Kakati]

Hi Alistu, in the 1st paper there is one graph for OSNR (in dB) versus Power penalty (in dB) so can you please tell me how to calculate the power penalty i mean which component can measure the same. Thanks for the reply.

Regards

[alistu]

This issue is explained by the first few lines after the figure in the paper. OSNR refers to signal to crosstalk ratio. So the author has once measured BER without crostalk, and then adding crosstalk of different levels, they have measured BER again, which became worse this time. In order for this BER to become equal to when no crosstalk was there, they have added more input power. The value of the added input power for which the system with crosstalk acts as good as the system without crosstalk (in terms of BER) is the power penalty of the system.

Regards

[Dr. Dhiman Kakati]

Hi Alistu, Thanks for the reply, as you have mentioned I have to make a table measuring the input power to be added to the system and respective OSNR i note down then the plot will become like that one in the paper. Thanks for the help. I will try for my system.

Regards,
Dhiman

[alistu]

You’re welcome. That’s right. In order to find power penalty, you might have to use iterations in OptiSystem to add several amounts of input power and see for which the resulting BER would be the same as the one in case of no crosstalk, to find the exact power penalty. This is the part which might take some of your time.

Regards

[Dr. Dhiman Kakati]

Yes it would be a time consuming task, still i will try to find after the completion of my design. and thanks Alistu for your encouraging support.

Regards,
Dhiman

[alistu]

You’re welcome Dhiman.

Cheers!

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