SMF – attenuation versus wavelength

[Sasha]

Hello all,

I tried to get attenuation versus wavelength output and I obtained the output. I want to know why I am getting these attenuation values for SMF? and what are the parameters used to calculate attenuation and what formula used?

I used 1km optical fiber SMF, CW laser power=0db

I have attached the results

Thanks in advance.

[alistu]

Hi Sasha,

The attenuation of the fiber is calculated by considering different factors each causing signal attenuation by themselves, such as infrared and ultraviolet absorption and Rayleigh scattering. Please see the attached image which shows how these factors contribute to fiber attenuation and how their all in all effect is considered to calculate total fiber attenuation (the peak is due to OH absorption at that wavelength).

[lavanya krishnan]

hello sasha ,
may I know how to get curve attenuation vs wavelength? what optical visualizer we have to use

[Alessandro Festa]

Hi Sasha, the table you posted does not seem correct for wavelengths <1400nm, attenuation should be higher! What fiber did you use for propagation?

[Sasha]

Hello all,

Thank you so much for your response.

Lavanya,
I didn’t use any visualizer. I used SMF fiber with the length=1km, attenuation=0db/km, CW laser power=0db and then I changed the wavelength of laser and fiber wavelength and checked the attenuation output. I am not having the osd file now. So I am attaching the picture of layout diagram.

Alessandro,
I used SMF optical fiber. I do remember they have given attenuation values in help section for wavelengths from 1400nm. I got the same values as output. I want to know how they got these values?

Thanks in advance

[Alessandro Festa]

Can you attach the design or the Att vs Wavelength for the fiber you are using?

[Sasha]

I implemented simple optical system transmitter(consists of Pseudo random bit sequence generator,NNRZ Pulse generator, CW laser and Modulator) receiver(Photodetector APD and low pass bessel filter), link as optical fiber SMF and power meters to view the output at CW laser(0db), Modulator(-3db), optical fiber and photo detector. Visualizers used to display the bit sequences.

Thanks in advance.

[Alessandro Festa]

Hi Sasha, this info does not help too much in understanding why you get wrong attenuation results. What is the file for attenuation vs wavelength you SMF fiber is using?

[Dhananjay Patel]

Hi Sasha,

Can you please tell us, how are you measuring the attenuation.

Besides, I hope you are changing the laser wavelength and the fiber reference wavelength at the same time. I agree with Alessandro, in the sense that in first and second window of wavelengths the attenuation should be maximum. Instead you are getting best results there. Lets us know about it?

[Sasha]

Yeah you are right. I am changing the wavelength of the laser and optical fiber simultaneously. Now I have given sweep for both CW laser and Optical fiber from wavelength 200nm to 1600nm. When I checking in the report, I am able to see the output for wavelength from 1400nm to 1700nm.
I attached a osd file and picture of output here.

Thanks in advance.

[Sasha]

I want to know why I am not getting output for other wavelength?

Thank you

[Alessandro Festa]

You should also attach the “attenuation.dat” file referenced in your osd.

[Sasha]

I used the builtin file ‘attenuation.dat’ file

[Sasha]

Here I have attached attenuation.dat file. Here they have specified for wavelength from 1400nm to 1650nm. And in help section, they have mentioned that attenuation is calculated by using linear interpolation method. I have attached that picture also. I want to know what are the parameters they used to calculate?

Thanks in advance.

[Sasha]

I am not able to attach the .dat file. So I copied into word document and attaching it. Take a look at it.

[Alessandro Festa]

Hi Sasha, the file you attached only has attenuation data for wavelength >1400nm, so it makes sense that your results below 1400nm are not correct..you should try to use a different file starting from a lower wavelength, if possible measure your fiber in the lab.

[Sasha]

Yeah okay. But how did they calculate the attenuation values given in .dat file. I want to know that.

Thanks in advance.

[Author]

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