Fiber optic tutorial?

[g***@gmail.com]

Hi all, I'm mostly trying to pick the right fiber collimation/ coupler to get a laser beam (or other source maybe) into a fiber. Fiber is multi mode 63 um diameter core, NA= 0.27. The laser source is ~800nm. I was looking at these
on thorlabs
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=944&pn=F220FC-780
(You'll have to scroll down.)

Do I want to pick a coupler with a lens that matches the NA of the fiber to
get the most light into the fiber?

Does the beam diameter tell me the maximum beam size that will make it into the fiber?
(Sorry for the rather simple questions.)

George H.

[JTS]

Post by g***@gmail.com
Hi all, I'm mostly trying to pick the right fiber collimation/ coupler to get a laser beam (or other source maybe) into a fiber. Fiber is multi mode 63 um diameter core, NA= 0.27. The laser source is ~800nm. I was looking at these
on thorlabs
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=944&pn=F220FC-780
(You'll have to scroll down.)
Do I want to pick a coupler with a lens that matches the NA of the fiber to
get the most light into the fiber?
Does the beam diameter tell me the maximum beam size that will make it into the fiber?
(Sorry for the rather simple questions.)
George H.

Hi

you should choose a combination beam/lens that will not exceed the NA of
the fiber. If you exceed it, some light will not be trapped.

By that combination, you should be able to focus the light into a spot
smaller than the core (since the core is 63 micron, it will be so if you
focus with NA at least 0.01 approximately).