Small tube for a 400 micron optical fiber

[drodrig]

Hi there,

We want so measure the light on a 8mm hole. For that we will scan the positions inside (x-y) with a 400 micron fiber. We have two linear stages in order to move the fiber (in a counterlever position) across the hole plane.

For that we need a tube of around 500micron diameter (we will fit the fiber with glue, then we polish the front). I asked in our workshop and they can not make a hole deeper than 5mm. The other problem is the outer diameter of the tube.

I guess one can buy directly a tube. This is what we need:

Inner diameter: 500 microns
Outer diameter: 1000-1500 microns
Length: 20mm (1 inch)

Does anybody know if one can buy a tube like this?

We have some FC/PC connectors, I thought we can machine one, but it is not the best solution

thank you
regards,

 

[IRstuff]

Why not just use a camera to image the hole? You'd get easily a factor of 10 better resolution. A 1080p camera would have 1000 spatial samples of the hole in each direction; the FPA guarantees orthogonality of the rows and columns.

TTFN
I can do absolutely anything. I'm an expert!
faq731-376 forum1529

 

[drodrig]

Interesting idea,
we haven't thought about a camera. I'll tell my colleagues.

The idea is our "reading" fiber will go to a photomultiplier, which is supposed to have a very good resolution.

cheers,

 

[IRstuff]

Sure, but you're running it through a 400 micrometer aperture, so resolution is limited from the get-go. And, the fiber has a relatively large capture angle, so that also limits resolution. A single pixel on a camera won't be able to see much beyond its own dimensions in an imaging system, so resolution is inherently better. The only case where resolution for the PMT might be better is if you're stepping the fiber at extremely small steps, say micron or sub-micron, to oversample but, again, the 400 micron aperture kind of makes that a bit moot. Typically oversampling at anything finer than about 1/8 of the pixel resolution (50 microns) would be not worthwhile, while even a run of the mill HD or higher resolution camera would have the equivalent of sampling at 5 microns or finer, without oversampling.

If you're using a PMT, does that mean you're expecting very low signal levels? That might be a non-starter for most cameras. Since you'd have to scan the PMT to get what you want, the intensity profile needs to be stable for the duration of the scan, which could provide a reasonably sensitive camera enough integration time and frame integration to make up for the poorer SNR.

TTFN
I can do absolutely anything. I'm an expert!
faq731-376 forum1529

 

[jedward]

look under the heading for Hypodermic tubing
I found microgroup.com

 

[drodrig]

Hi there,
Apparently my colleague wants to use the PMT to be able to count photons.

We finally will machine a kindof cone with a small tip

thanks to all!