fiber optics for metal heating?

[coppercone2]

What kind of fiber optics would allow enough laser light to pass to heat small coils (like filaments) to red heat?

Cost, workability, manufacturers, etc?

[Fraser]

Thermal imaging topic ? 

[eKretz]

Lol. At least he got thermal in there. 

[coppercone2]

Its related to optics. Are we limiting power levels in this forum?

[Fraser]

It is simply that fibre optics are not commonly found in thermal imaging applications and definitely not for heating something like you describe. Your description of the requirement would be closer to laser engraving or cutting. Very high power lasers and optics are sometimes involved with such.

You can look up the losses for fibre optic bundles and calculate the energy you need to present to the target source to raise its temperature. That will then provide you with the power of laser required to drive the system. If there is too much loss in the fibre optic bundle you will need a better or larger type. The focussing optics will need to be matched to the wavelength in use and should be designed for the power passing through them

This is all stuff available via Google and relating to laser engraving or cutting.

It is not really something I would expect thermal imaging enthusiasts to have an in depth knowledge of. Your question would be better served in a more generic area of the forum if you truly want useful answered from a large cross section of knowledgeable people. I know this sub forum is particularly helpful and full of great people, but why limit yourself ?

Please feel free to post in a less than optimal forum, but you are a tad off base asking about fibre optics here and the laser need not be 10um CO2 so expensive thermal imaging optics are not essential.

I hope this explains things for you

Fraser

[Fraser]

As a side comment, I have yet to see a fibre optic cable used to heat a target beyond your typical power meter sensor head. There must be some serious reason for taking such an approach. Fibre optics operate on internal reflection but such is not normally 100% so things can get really 'interesting' when using them to carry high energy laser energy ! Non contact or stand-off heating can take many forms. Induction heating or even direct illumination from a powerful laser may be used. The surface finish of the target is important when heating via laser illumination though. If the surface is shiny, very little energy will enter the target. But then you should know all this already.

Enjoy your experimentation and remember your health and safety measures !

Fraser

[coppercone2]

Relating to safety, i assume the cables have a metal braid or use some kind of coupler to make sure the laser did not burn through the cable and be emitted elsewhere? When i think about it, having mirrors in a raceway seems good enough since the ease of routing is bypassed by requirements for safety if you need to put it in a pipe or something so you dont get a situation like the early half life games.

I thought the technology would exist to make thermal boroscopes though.

[Marco]

What kind of fiber optics would allow enough laser light to pass to heat small coils (like filaments) to red heat?

Cost, workability, manufacturers, etc?

Googling for "multimode fiber max fluence" turned up this on the first page. End capped fiber assembly seems what you want to search for.

The power seems to not be a problem, the costs might.

[Fraser]

Thermal borescopes exist. They use rigid tubes and lens elements within. Surface coated mirrors can be used for off axis viewing etc. They are very expensive ! Losses are also quite high due to the small aperture.

Thermal flexible and/or steerable borescopes/endoscopes ..... now that is a whole other ball game

Fraser

[mikeselectricstuff]

As a side comment, I have yet to see a fibre optic cable used to heat a target beyond your typical power meter sensor head.

There are lasers with fibre outputs that can output many tens of watts, which will certainly get things nice and warm

e.g.
https://www.lasercomponents.com/uk/product/fiber-coupled-high-power-laser-diodes/

https://www.ebay.co.uk/itm/Coherent-Laser-FAP800-16W-808nm-16-watt-fiber-coupled-output-New-old-stock-/163314742454

This can have interesting consequences if the fibre gets damaged

https://youtu.be/qDxcGHWK3vU?t=38

[Fraser]

Excellent example Mike But this proves my point to the OP. I am a thermal camera specialist and have not come across fibre optic heating of targets beyond the use of heated power meter targets that use thermopile technology   That does not mean such does not exist though   This is why I recommended a more generic area of the forum to canvass more clever and knowledgeable people like yourself

Fraser