If I had no conscience I could be a millionaire

[HankB]

. . .  the nitrogen "had smaller molecules so it didn't leak as bad as air". . .

So smaller molecules don't leak as bad?

I could retire a billionaire by this time next year if I didn't have a conscience or didn't mind taking advantage of all the idiocy that parades as common sense these days.

Brad, PM me. I don't have too many qualms about taking advantage of idiots. If you have a "billion dollars in a year" idea that doesn't involve selling drugs, swindling elderly widows, or getting me a stay in the Graybar Motel, I'll split the take with you.   

[230RN]

Yes, you can get pure deuterium in cylinders.  I'm not sure I recollect exactly, but isn't it used as a calibration gas in mass spectrometers or something?  I remember seeing it in a "lecture bottle" (a small cylinder about 3" diameter X about 12" in length) in a lab I worked at once.

The joke was that if you burned it, the steam cloud thus formed would fall straight to the floor with a soft "flump" sound.

I also saw a bottle of "Carbon Dioxide, Bone Dry" on the shelf and was amazed that "Bone Dry" is actually a technical term.  Would you believe it actually means just that, "bone dry?"  (No water to form carbonic acid in the bottle.) Who'd'a thunk it?

Terry, 230RN

[HankB]

Yes, you can get pure deuterium in cylinders.  I'm not sure I recollect exactly, but isn't it used as a calibration gas in mass spectrometers or something?

In fiber optics, deuterium is sometimes used as an alternative to hydrogen loading before writing a fiber Bragg grating - it shifts the absorption peak and reduces absorption losses.

[280plus]

In fiber optics, deuterium is sometimes used as an alternative to hydrogen loading before writing a fiber Bragg grating - it shifts the absorption peak and reduces absorption losses.

Alright, way too much google time necessary to be figuring all that out. 

 

[Ned Hamford]

:smiles and nods:

[HankB]

Alright, way too much google time necessary to be figuring all that out. 

Here's the simple & abridged version, skipping a lot of the details:

Information is carried over fiber optics by laser light, usually in the near IR. If you can divide the laser wavelength into really tiny "slices" you can carry more information. This requires filters.

Spectral filters are made by putting together a "stack" of materials with varying index of refraction. If you zap an optical fiber from the side with an ultraviolet laser in the right way, you can change the fiber core's index. Do this in a controlled manner, and you can get a "stack" of different indices in the core that's really long, with a really narrow bandwidth. (This is called a fiber Bragg grating.)

Now, the fiber itself isn't naturally very sensitve to being laser irradiated, but if you let it "soak" in a high-pressure hydrogen atmosphere for a while, the hydrogen diffuses into the fiber and increases it's sensitivity to UV laser irradiation. This is normal SOP. However, the hydrogen can form OH groups that for some wavelengths cause absorption, making for a "lossy" filter. Using deuterium rather than hydrogen shifts the absorption peak and reduces losses.

[280plus]

I think I understand most of that surprisingly enough. Thanks! 

[Tallpine]

I have a conscience to sell if anybody's interested 

[230RN]

How come the hydrogen (or deuterium, for that matter) doesn't diffuse back out of the fiber?  Or is this done during the fiber's drawing so it's really captured in there good and tight?

[HankB]

How come the hydrogen (or deuterium, for that matter) doesn't diffuse back out of the fiber?  Or is this done during the fiber's drawing so it's really captured in there good and tight?

Good question!!     The hydrogen doping is not done during the draw, it's done long afterward. The high-pressure loading is temporary - if you store the loaded fiber at room temperature the hydrogen or deuterium will diffuse out. If you want to keep the hydrogen loaded fiber on hand for a while, you store it in a freezer at -40 degrees.

After writing a grating, you anneal the written area of the fiber at 300 degrees - this drives off any remaining hydrogen and stabilizes the grating. Annealing changes the characteristics in a predictable manner, and since you know in advance what your final target is, you offset your process accordingly.

[Perd Hapley]

If I had no conscience I could be a millionaire

So THAT's JamisJockey's secret!