Optical Fiber – Attenuation

[Sasha]

Hi All,

I tried to implement an system design power budget with optical fiber. My transmitter input power = -3.218dbm and optical fiber length = 1km, attenuation = 2.61dm/km and I am getting total power output as -7.614dbm. It shows total power loss = 4.396dbm but in link I am having a loss of only 2.61db.

In optiwave sample files they have shown the system design power budget file by using attenuator and they are getting exact output.

Here I attached the file.

Thanks in advance

[Sasha]

Optiwave system design power budget file

[Abhishek Shrama]

Hi Sasha
The optisystem sample file that you have attached is providing results to me in required manner.In file the attenuater is set to 27dB and overall power after attenuation is -30.010.Transmitter laser power is 0dB and after MZM comes out to be -3.010dB due to insertion losses and all.
I have tried by deleting attenuator and inserted a SMF of same attenuation i.e 27dB .I got the same results with fiber and attenuation.Value at BER is also same order of 10^-9
Try it as i said and if there is than any problem let me know
Thank you

[Abhishek Shrama]

Since i am using a older version of optisystem so could not able to upload the system file.However as i stated above by taking value of attenuation 0.2dB/Km (default in optical fiber lib. component SMF) you can test it.
Kindly see the screen shot of the system ,i have calculated the value of fiber as
135Km x 0.2dB=27dB
Which corresponds to the attenuation value at attenuator

[MHD NA]

Hi Sasha;
you have some mistakes in calculation the required length of fiber, so you should modify its length and observe the output power to reach to wanted value which is corresponding to fiber length.

Regards,

[Abhishek Shrama]

Hi! Mohammad namera,I think this would be the case that author didnt get desired power at output.Since it works fine for me without any issue.Thank you for your help
I just did basic calculation and got desired results

[Sasha]

Hi Sharma,

when using the SMF, I got the attenuation output as -30db.Actually I want to get the output for multimode fiber. And when I am giving the same attenuation and length for MMF fiber and I am getting total output power = -33.4db. What is the change should I do in MMF fiber?

Thanks in advance

[Sasha]

Hi Mohammed,

I tried as you said for MMF fiber and SMF fiber. It worked for SMF fiber but not for MMF fiber. What is the change should I do in MMF fiber?

I fixed the values as
Source power = -3.148db
attenuation = 0.2db/km
length = 135km
then I should get the total power output = -30.148db
but instead of that i am getting total power output = -33.426db

I attached the file here.

Thanks in advance.

[alistu]

Unfortunately, I don’t know the exact reason for the attenuation caused by the fiber to be more more than the attenuation value given and I couldn’t find a reason from the help section. But I am guessing maybe the 0.2 dB/km attenuation is for the center wavelength (or frequency), and as the frequency changes, the attenuation exceeds the defined value.

[Author]

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