Gain parameter in OFDM 12 demodulator

[Mohamed Ben zegalamParticipant]

Hi All,

I notice that the gain parameter in the OFDM 12 demodulator has high value in some optisystem samples (almost 17000), also it look like a factor not dB value as the gain of the amplifiers.
is there some one has good knowledge about this parameters.

[alistuParticipant]

Hi Mohamed,

Based on my own experience, I think this parameter plays a part in determining the optical power of the signal after being converted into light, while we expect the optical power to be determined by the laser, and not by the electrical power. Nonetheless, I don’t know its exact function either.

Regards

[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.

[alistuParticipant]

It can be understood why when the gain in system (amplifiers, laser power,…) increases, the OFDM modulator gain should sometimes be decrease3d for better results, and the reason may be the nonlinear effects, but what you have mentioned about the effect of OFDM demodulator gain on the results is really strange (and yet it happens)… unless there is saturation and so on.

[Damian MarekParticipant]

The gain boosts the output signal by a factor. The gain is not given in dB!

[Mohamed Ben zegalamParticipant]

Hi Damian,

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