What's the mode of light in single-mode fiber?

[iVenky]

Hi,

We talk about single-mode and multi-mode fiber and I assume they talk about the way of sending just one modes (TEM or TMmn or TEmn). Which mode is generally used for single-mode fiber? Is this set by the geometry of the single-mode fiber (especially the opening)? Also, this means that the source of light should have the same mode, right?

 

[davenn]

Hi,

We talk about single-mode and multi-mode fiber and I assume they talk about the way of sending just one modes (TEM or TMmn or TEmn). Which mode is generally used for single-mode fiber? Is this set by the geometry of the single-mode fiber (especially the opening)? Also, this means that the source of light should have the same mode, right?

what research have you done so far and what has that reading told you?
give some links you have read and let us know what bits you need clarification on

 

[iVenky]

what research have you done so far and what has that reading told you?
give some links you have read and let us know what bits you need clarification on

Hi Thanks for the reply.

I was just studying about single and multi-mode fiber online. Since it says single-mode fiber, I assumed that it sends only one of the modes of the electromagnetic wave, but don't know which one.

 

[davenn]

Hi Thanks for the reply.

I was just studying about single and multi-mode fiber online. Since it says single-mode fiber, I assumed that it sends only one of the modes of the electromagnetic wave, but don't know which one.

googling your question

which mode is used in single mode optical fibre ?

brings up many links ...

https://www.bing.com/search?q=which...s=n&sk=&cvid=8751a3d4893a4345977238848959c110go have a read and see if your question gets answered
if you are still struggling, then give one of those links and tell us what part you don't understand Dave

 

[tech99]

This is quite a good description:-
https://www.rp-photonics.com/lp_modes.html

 

[iVenky]

This is quite a good description:-
https://www.rp-photonics.com/lp_modes.html

This is exactly what I was looking for. So the dominant mode is LP01.

 

[BPHH85]

This is exactly what I was looking for. So the dominant mode is LP01.

Single mode, in any optical context, always means the lowest order mode. In principle, that's the LP01 or gaussian mode. Whether a fiber is single mode or not depends strongly on the wavelength of the guided light, as the V number is inversely proportional to the wavelength. It's the same with laser light. If the beam is meant to be single mode its intensity profile is always gaussian. But as anything in the world, there is no 100% perfection. So even in single mode, some percentage of the light might be in higher order modes. But these percentage a in general negligible for dominant single mode opperation.