[Mohamed Ben zegalamParticipant]

Hi Nithin,

I do not understand why do you use S/P converter after PRBS. if you would like to transmit the same data, you can use fork instead of S/P converter.

Your design did not work because
1- the input of the QAM sequence generator have to be in serial (not in parallel like what you have in your design)
2- as far as I know, when you use the S/P converter you are not copy the data to two OFDM system. S/P will divide the data to two output (for example the PRBS generate 101110100101 so the output of the S/P will be:
output 1====> 111100
output 2====> 010011

kind regards
mohamed

[Mohamed Ben zegalamParticipant]

Hi Ranjeet,

for the Capture10, as I can see the Q-factor is not mach the BER, please may you change the algorithm parameter to Gaussian instead of measuring. I think this will make the Q-factor mach the BER.

Thanks!

[Mohamed Ben zegalamParticipant]

Hi kumar,

In order to understand how the optimization work in Optisystem, you need to look to the optisystem_Tutorial-Volume 1. There are many optimization examples the basic one example is (SPO optimization—System margin).

Kind regards
Mohamed

[Mohamed Ben zegalamParticipant]

Hi aadilqau,

As they mention before, there is no any formula or criteria that shows how can we choose or calculate sequence length or samples per bit. As far as I know, for the sequence length, you have to increase it as much as you can to get good performance in terms of BER for example. and for the sample per bit you can increase until the sample rate can cover the spectrum of your design (for example: if you have RF in range of 40 GHz, you need to increase the sample per bit until the sample rate be more than 80 GHz). however the RAM of your computer is also a factor for increasing both of them, so there is a limit of increasing these two parameters in order to avoid system shut down.

Kind regards
Mohamed

[Mohamed Ben zegalamParticipant]

Hi Ranjeet,

Your example is correct, and it is the same as my explanation. because

OFDM symbol period= 1/frequency spacing (dalta F).

so if you take frequency spacing (dalta F)= Bit rate/(log2(M)*Nsc), then

OFDM symbol period= (log2(M)*Nsc)/Bit rate, as per your example

OFDM symbol period= (2*128)/40Gbps

Kind regards
Mohamed

[Mohamed Ben zegalamParticipant]

Hi Ranjeet,

I agree with previous statements from Fayiqa Naqshbandi, Gokul Boro, and SAHIL SINGH. but first you need to know how to calculate the frequency spacing, then the subcarrier frequency will be as mention before

frequency spacing (dalta F)= Bit rate/(log2(M)*Nsc)

where the M is the M-array of the modulation, and Nsc is the number of subcarriers

hopefully this help you.

Kind regards
Mohamed

[Mohamed Ben zegalamParticipant]

Hi Alistu,

thanks for your reply. actually I am trying to make OFDM 12 work with phase compensate instead of pilot and channel estimation. do you know any paper study the phase shift in the optical transmission line

[Mohamed Ben zegalamParticipant]

Hi Alistu,

Please may I know what do you mean about “using matlab component and a program that would calculate the rotation and rotate the symbols back”
As far as I understand from this discussion that there is no such away to calculate the rotation. if I am wrong, what is the formula to calculate the rotation?, and if there is any paper discuss the rotation symbol in optical communication system please tell me.

thanks

[Mohamed Ben zegalamParticipant]

Hi Alistu,

sorry for late reply.
actually I am still working on it, in the attached file you can see the configuration of the OFDM PON that I am working with it (version 0). once I complete and improve the last version, I will submit it in the forum.

[Mohamed Ben zegalamParticipant]

Hi Damian,

I check the design that you attached in the link above, and I am thinking if I can use just one OFDM modulator with 4 ports at transmission side in the OLT. in the receiver side, we split the optical signal to four, then we down converter to RF each one spirit.

[Mohamed Ben zegalamParticipant]

Hi Alessandro

Thanks for your reply. The example is WDM PON from Metro and Access system folder. My project is
CO-OFDM. I know they are different design, but I just want to know why both
of them has different shape of BER curve while they have almost the same
value.and is mine is consider as good or not.

I already get the explanation from optisystem support team, and here their answer

“The reason your eye diagram looks like this is its connected after the
decoder and the NRZ generator, which means your signals can only have “zero”
or “one” and that’s why they look ideal. For a more accurate view of the eye
diagram, you have to connect the visualizer before a decision has been made
on the electrical signal. However, you can’t really do that on the OFDM
because the output is not actually electrical. The decision is made inside
the OFDM component.

By the way, you are using our old OFDM component, which to be perfectly
honest, is not very good. For better results, please switch to our latest
OFDM components. They are a huge improvement over the old ones. I think you
have to be using at least OptiSystem 13.0.3 for them.”

[Mohamed Ben zegalamParticipant]

[Mohamed Ben zegalamParticipant]

Hi Damian,

thanks for your reply, it normal for the gain to be too hight such as 10000.

[Mohamed Ben zegalamParticipant]

[Mohamed Ben zegalamParticipant]

Hi Alistu,

thanks for your reply, I think this parameter is increasing the signal some how inside the OFDM demodulator, because I notice when I increase the gain then amplitude of the constellation increase, and when I decrease it then the amplitude is decrease it also.
moreover, if I increase any gain at any amplifier (electrical or optical ) before the OFDM demodulator or the power transmitter then I have to decrease the gain at the OFDM demodulator to get better results.