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I use 100 Gb/s QPSK signal transmitted over 1000 km of SMF and the effect of non-linearity when calculating Q-factor appears at 3 dB when using non-linear coefficient n2=1e-19 ,Aeff=80 , are this parameters practical ? as the typical value of n2 around 3e-20 but it doesn’t affect the value of Q-factor (non linearity doesn’t appear).

### Responses (7):

• #20063 Participant

I use 100 Gb/s QPSK signal transmitted over 1000 km of SMF and the effect of non-linearity when calculating Q-factor appears at 3 dB when using non-linear coefficient n2=1e-19 ,Aeff=80 , are this parameters practical ? as the typical value of n2 around 3e-20 but it doesn’t affect the value of Q-factor (non linearity doesn’t appear).

• #20064 Abdallah Ismail
Participant

If the units of the values that you’ve mentioned above for n2 in m2/W and for Aeff in um2
you’ll find that gamma will be equal to 5 (1/(w.km)) and this a very large value that will affect Q factor.
The possible reason that i think,perhaps you use a DSP component that has a phase correction algorithm (CPE) which correct the phase error due to the nonlinearity and you should disable it in the DSP.

+1
• #20066 Abhishek Shrama
Participant

Abdallah i have n2= 26×10^-21 and Aeff =80 then how to calculate value x/Km/W???
What is formula to calculate Gamma??

• #20072 Abdallah Ismail
Participant

Dear Abhishek Shrama,
I attached a picture for the formula

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• #20076 Abhishek Shrama
Participant

can we take vary value of gamma arbitrarily??
I saw it to be 1.3/km/w and 5 in some paper. can I change it ?

• #20079 Abdallah Ismail
Participant

It is a characteristic of fiber depend on the manufacture

• #21603 Ajay Vyas
Participant

Thanking you sir
this is very useful to solve my problem

• #21607 Alessandro Festa
Participant

Dear Mai, you are not mentioning the launch power level into the fiber…if it is too low, Q-factor may not be affected by non-linearity.