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UltravioletPhotography

IR, visible and UV of small blow torch flame


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Hi Colin, yes that ties in with what I was always told about the hottest part of the flame. Nice demo with the wood.

 

My previous life was playing with plasma. My PhD was on the use of low temperature plasmas to produce metal films. I wish I'd had my UV camera equipment then.

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  • 4 years later...
enricosavazzi
On 4/11/2019 at 8:33 AM, Andy Perrin said:

Which reminds me of a question I had— don’t fibers only admit certain modes/wavelengths that depend on their diameter? Is that only an issue for you guys with really thin fibers or do you get a cutoff wavelength that’s in the range you can measure with the spectrometer?

The data fibers I use are the most common types and have core diameters 62.5 or 50 microns (for multimode fiber) or between 8 and 10.5 microns (for singlemode fiber), so much larger than VIS (and UV) wavelengths. There are also differences in how the fiber ends are polished (flat, slightly convex, or slanted by 8 degrees). An additional characteristic of data fiber is that it is optimized for NIR transmission between 850 and 1300 nm for multimode, and both 1310 and 1550 nm for singlemode. Ordinary data fiber is not used with VIS or NUV, and I should expect NUV to be absorbed (especially in singlemode fiber, which can reach lengths exceeding 80 km between repeaters).

One not-frequently-mentioned fact is that the 1310 and 1550 nm wavelengths for singlemode transceivers have been chosen to avoid the water absorption peaks. At multi-km lengths, small amounts of water in the fiber material may cause a significant absorption. Low-water-content singlemode fiber is also available, at premium prices. Multimode fiber is only used for short-haul connections up to a few hundred m, so not a problem here.

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