Home Forums SYSTEM BER analyzer eye height units

• Author
Posts
• #27512
Dr. Dhiman Kakati
Participant

Hi all,
We all are familiar to the BER analyzer, but I am confused about the units of eye height.

Regards

• #27513
Abdallah Ismail
Participant

The eye diagram is two pulses plotted one up and one down inverted. To appear like the eye.
So it is a unit of pulse amplitude.

• #27514
Dr. Dhiman Kakati
Participant

Hi abdallah, I am not clear “So it is a unit of pulse amplitude.”

Regards

• #27515
alistu
Participant

Hi Dhiman,

I believe Abdallah means since the plotted figures are two pulses, the measurement unit is also their unit, which is “pulse amplitude” unit. You might have noticed the label “Amplitude (a.u)” for the amplitude axis. Here a.u. stands for Amplitude unit, as Abdallah mentioned.

Regards

• #27517
Dr. Dhiman Kakati
Participant

Oh thank you Alistu for making me clear. will it be volt..? or other

Regards

• #27521
alistu
Participant

You’re welcome Dhiman. In my opinion, he fact that the amplitude unit has not been named there means we can not say it is either voltage or some other parameter for sure. And I have noticed in some other forum topic discussion that it CAN be considered as voltage, but it is not necessarily that.

Regards

• #27535
Dr. Dhiman Kakati
Participant

Thank you Alistu for sharing your knowledge.

Regards

• #27536
alistu
Participant

You’re welcome.

Cheers!

• #27566
Jamal
Participant

Can anyone explain the metrics , ‘Threshold’ ‘BER Pattern’ and ‘Height’ in BER analyzer ?
Regards

• #27571
alistu
Participant

Hi Jamal,

Threshold is a value based on whose value the binary signal logical value is being decided. If the value of the signal is less than threshold, it is considered a ‘0’ and otherwise, a ‘1’. BER pattern refers to the BER figure versus bit period time. And “Height” refers to the eye opening in the eye pattern, which shows the quality of the signal.

Regards

• #27575
Jamal
Participant

Thank you Alistu ðŸ™‚
Also can you tell what are the optimum values for these metrics ?

• #27580
alistu
Participant

You’re welcome Jamal. One can’t really say eye opening or BER have an optimum value. The more the eye opening, the less the error and therefore, the better system performance achieved. The minimum acceptable Q-factor for the systems is usually 6 or 9, which correspond to BER=10e-9 and BER=10e-12.

Regards

• #27591
Jamal
Participant

Thank you Alistu

• #27592
Jamal
Participant

Alistu, how is BER related to Q factor mathematically ?

• #27593
alistu
Participant

You’re welcome. You can refer to the following pdf file that is attached in the post in the forums topic I am addressing below. Both these parameters correspond to the eye opening and you can see where Q-factor increases, BER decreases in the BER analyzer figures.

VALUE OF Q IN ENCRYPTED SIGNAL

Regards

• #27651
san lymit
Participant

Dear everyone,

Could anyone tell me how to increase Q-factor and minimum BER? For example, we need to increase power at the transmitter, put the amplifier at the transmitter and transmission line?

Best regards,

• #27654
Dr. Dhiman Kakati
Participant

Dear San,
the BER will be minimum and Q-factor will increase only when your system design will be efficient one i.e. you have to adjust the parameters of the components, use some advanced modulation scheme such as DQPSK or QAM at the transmitter side and also go for OFDM which is found to be more immune to error. Regarding the fiber channel you can use optical amplifier such as EDFA to compensate for signal attenuation, then you can go for dispersion compensation i.e. you can use use dispersion compensation fiber for reducing the dispersion that will help you to increase the Bot rate of the system. At the receiver side DSP block you can use which is consist of many filters or algorithm such as DC blocking, Normalization, Low Pass Filter, Resampling, QI Compensation, Dispersion Compensation, Nonlinear Compensation, Timing Recovery, Adaptive Equalizer, Frequency Offset Estimation etc. that will help you to get a better result in terms of BER and Q-factor. Moreover it will be design specific such as which detection scheme you are using (homodyne or heterodyne).

Regards

• #27670
alistu
Participant

Hi San,

Aside from the above suggestions, you can also change the lasers linewidths in many cases to a value much less than the default value. And you should be careful with increasing the launched power, as in high powers the nonlinearities might step in. And try to use amplifier gains proportional to your channel attenuation, since amplifiers have noise figure which results in signal degradation instead of better performance in case of excessive use.

Regards

• #29067
Dat Tran
Participant

hi alistu!
I have attached the project. I am using 16 QAM, I want more DSP blocks for 16 QAM in the collection. I have to put in any position DPS blocks in my project?