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(joined October 2014)
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How can we determine maximum transmission distance of link.

### Responses (11):

• #22409
K. Esakki Muthu
Participant

How can we determine maximum transmission distance of link.

• #22415
Ashu verma
Participant

Hello esakkimuthu
Generally to obtain the maximum link distance,system for maximum length for which your BER would between the range of 10^-9 to 10^-12 and Q-factor 10 is your maximum achievable distance.You can calculate the Q-factor from BER and BER fro Q factor using There are many ways to enhance the maximum achievable distance by using efficient modulation techniques,accurate amplification etc.

Eye diagram

https://www.utdallas.edu/~dlm/3350%20comm%20sys/T-REC-G.Sup39-200602-I!!PDF-E.pdf

+5
• #22418
K. Esakki Muthu
Participant

Dear Sam Sung

Thank you for your kind information.

One more question.
say for example i am having a 20 km link with 0 dbm input power , 4 dB amp for loss compensation and the BER is 10^-12, if I use 10 dB Amplifier, whether my my link distance increase or not?

Best Regards,
K.Esakki Muthu

• #22646
Ashu verma
Participant

Thank you essakmathu
I hope link is working for you as alessandro suggested you.Also he made a very good point about amplifiers from the concern of non linearities.Best of luck for research and let us know if you will need help regarding other topics

• #22419
Alessandro Festa
Participant

Hi easkkimuthu, the link is not working simply because the hyperlink is not on the full address, so you should copy and paste the following into the address bar of you browser:

Regarding your question: I suggest a good book like Agrawal – Fiber Optic Communication Systems to have a basic knowledge of this matter.
Amplifiers are used to increase the link distance, but there are many factors to take into account (where they are placed – booster or preamplifiers? Their Noise Figure, if they create nonlinear impairments….) that it is better to start having some techincal background on this.

I hope my answer helps you, otherwise feel free to ask more clarifications!

Best Regards,

Alessandro

+1
• #22436
Abhishek Shrama
Participant

Heyy! esakkimuthu
The general idea by allesendro is appreciable. You can easily enhance the transmission length of your system by using amplification as a booster or pre amplifier.
According to example you have given if you are using 20 km SMF having attenuation 0.2dB/km then total loss is 4 dB. So if you are using a 4 dB optical amplifier then it will boost the signal to overcome the degradation by fiber. and if you are using edfa or raman 10dB gain then you will transmit your signal for longer transmission length within acceptable BER limits. again it all depends upon parameters of fiber and noises in amplifiers too. More the power, more the non linear impairments. Check your system for non linear parameters of fiber and noise in amplifiers you are using.

• #22650
alistu
Participant

Hi Abhishek,

Are you suggesting that that when the overall power attenuation caused by fiber is for example 4dB, if we use in-line amplifiers with a gain of 10dB, for example, we have a better transmission of data in the sense of BER? I think if our gain is more than attenuation, then because of the amplifier’s noise figure the extra gain might even corrupt the constellation diagram. Do you agree with me?

• #22657
Ashu verma
Participant

Hi Alisthu
You raised a good qeuery,but i think(as i understand from reply) he made clear that it depends upon gain noises and fiber parameters too.And statement also given by considering fiber non linearities.

• #22661
alistu
Participant

Hi Sam Sung,

In Abhishek’s statement, there was a mention of a 4dB attenuation and a 10dB gain and the system improvement as a result of that, which I was referring to. Otherwise, you are absolutely right about the nonlinear effects and the fact that they limit system performance if the power (whether launched power or amplified power) exceeds an amount.

Cheers

• #22469
K. Esakki Muthu
Participant

Thank you very much Alessandro Festa and Abhishek Sharma for your useful information and support. Thans a lot

• #22648

Good explanations from all. Thanks for the clarity in your information.