fiber inversion

[vignes]

dear damian,

what does mean fibre inversion in EDFA system, and

2.when we decrease the pump wavelength from 980 to 840, 640 for their respective energy level, what parameter will chane like gain or any internal parameters

3. the edfa spectral region is 1530-1560 . how can increase the spectral band to further

[Damian Marek]

Hi,

1) Do you mean population inversion? This just basically means the Er ions (or any type of atoms/energy state) are largely in the excited state, so that stimulated emission/spontaneous emission are favored/possible.

2) The gain will noticeably drop since less photons will be absorbed (EDFA’s absorb in the 980 nm range). Try it yourself with OptiSystem and using a sweep!

3) If you want to change the band drastically you might need to use a different material or a Raman type fiber. Although there are some effects like temperature which can broaden the spectrum.

[vignes]

dear damian,

thank to u, and u said about raman fiber, how we could add with erbiu doped fiber, if any parameter need to change or manualy any modification either we have to change on erbium doped fiber

[Damian Marek]

We have models for Raman gain both in the Bidirectional fiber and the specialized models in the Amplifiers Library->Optical->Raman folder. Raman gain is a different mechanism for creating a gain medium, so you would not be able to use the Er doped model.

[Alessandro Festa]

You can increase the region to L band (1570-1610nm) by increasing the active fiber length

[vigneswaran]

dear
Alessandro Festa , i followe ur question that , if we incresing the fiber length by keeping input pump power constant, the gain drastically reduces, the optical amplifier length will be around 10-40m, i asked u to refer fr that

[Alessandro Festa]

Dear Vignes, you need to increase pump power to get the same gain. Usually L band amplifier have much less efficiency than C band, so they are pumped at 1480nm where efficiency is better (but NF is lower).

[vignes]

dear friend,

thank to u…. and i plan to design edfa wave guide , so far i need some schematic model , kindly attach if any at sight of u

[Ravil]

Hi Damian, I have a followed question: what is the main purpose to use short-wavelength and high energy pump (840nm and 640nm)? For bigger increase of population inversion?

[vigneswaran]

dear ravil,

if we short the pump wavelength , the energy will be more, but the conversion efficiency is low, due to the exists if EXCITED STATE OF ABSORPTION , and the emission will be only between 2 energy levels, if u increase the energy levels, the population inversion not optimizing properly, i might be thought , that u can increase the erbium concentration on core ..

[Damian Marek]

Hey Ravil,

640 nm pump for an erbium doped fiber? I am only familiar with the 980 nm and 1480 nm pumping wavelengths with their respective characteristics of good noise figure and good power efficiency. Do you have a paper where they pump in those ranges?

Regards

[Alessandro Festa]

Hi Ravil, another drawback of pumping <900nm is that those wavelengths are below the cutoff in erbium fiber. I think pumping at 640 and 840 makes sense only for erbium doped materials (not fibers), so that you can use high power free space pumps.

[siva rama krishna]

This is correct post for my question.
Can anyone briefly explain the difference between 980nm and 1480nm pumping for EDFA amplifier?
Accoring to my knowledge
980nm has better noise figure(immune to noise) than that of 1480nm
1480nm has high gain comapred to 980nm pumping.

Whether am i correct?

If any wrong please correct me.

Thanks
Siva Rama Krishna

[Alessandro Festa]

Hi Siva, what you indicate are the main differences between the two pumping methods, so you are correct.

[siva rama krishna]

But from following preamplifier example it is showing that gain at 980nm is higher than that of 1480nm.

Preamplifier

Please any clarify this.

[Damian Marek]

The problem is that the graph you mentioned is gain vs length of the amplifier. The 1480 nm pump region is more POWER EFFICIENT not necessarily higher gain.

Pumping requirements

Look at the graph here that compares the pump power to the experienced gain. The 1480 nm pump outperforms the 980 nm pump. Good question though I was confused too! The key here is that the 1480 nm is more efficient, but NOT higher total gain.

Regards

[vignes]

dear siva,

actually what u trying to work with edfa, let me know, since i can make it clear,

normally, 1480 has low efficiency to absorb erbium ions due to lower energy compare to the 980 so the gain some what with pump of 1480nm

[Damian Marek]

Hi Vignes,

As I mentioned the 1480 nm pump will provide a higher power efficiency. However, since the pump is close to the emission spectrum it essentially causes its own stimulated emission, which results in a lower gain and lower fidelity signal.

[siva rama krishna]

Thanks Damian for your clear explanation.

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