Optical fiber with cladding < 125um? (Either buy or make)

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My thanks to the group for their collective help on my previous couple
of questions.  I've got another one now.

For a sensing (not communications) application, I need optical fiber
with a cladding diameter < 125um.  (I don't care what the fiber diameter
is with the protective jacket - I'm going to strip that off anyways.)

I need <125um, and I'd like 50um to 75um.  (Less would also be
acceptible, but I think 50um to 75um represents a "happy medium".)

I've found lots of fiber with _core_ diameters in the range I want, but
nothing with an overall diameter in the range I want.  (I've checked
Corning, ThorLabs, Edmund Optics, Oz Optics, Melles Griot, and everybody
else I could think of.)

So, are there any suggestions for a company I might _not_ have thought of?

How about suggestions for a way to take, say, 62.5um core / 125um
cladding fiber and somehow shrink it down to the 50um - 75um overall
diameter I want?

I've had a few ideas on how to do this, but none of them seem very
practical to me.  [ 1) Scrape the cladding off with a razor.  2) Since
the cladding is generally some sort of glass, dissolve it in a weak
hydrofluoric acid solution until I'm down to the desired diameter.  3)
Heat the fiber and stretch it until I have the desired diameter.]

FWIW, I'm working with 654nm (red) light.  And since (as I mentioned
above) I'm working with a sensor application, not a communication
application, I don't much care about single-mode vs. multi-mode.  I
suspect multi-mode might actually be better for what I want to do, due
to picking up more of the light, but I'm not sure about that yet.

Of course, I'll need to cleave the end of the fiber once I've got it to
my desired overall diameter, so a solution that gives me the diameter I
want but which makes getting a clean fiber tip impossible won't work for me.

Any ideas?

Bob Pownall

Re: Optical fiber with cladding < 125um? (Either buy or make)

Bob Pownall wrote:
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Fibres usually make sensors worse rather than better.  If you have a
fume hood, HF is probably easiest.

You used to be able to get He-Ne fibre with about 50-um cladding
diameter, but I haven't seen it in awhile.  You might find some on Ebay.


Phil Hobbs

Re: Optical fiber with cladding < 125um? (Either buy or make)

Phil Hobbs wrote:
<Summary: Some suggestions about how to solve my problem.>

Thanks, Phil.  You are, of course, correct, that the fiber will make the
sensor work worse (if only from losses in the fiber and in the
connection) rather than better.  However, given my space/area
constraints, bringing the sensor to the signal is, I think, even less
practical than shrinking a 125um cladding diameter fiber.

I don't have any fume hoods in my lab, but there are some in a lab next
door.  I'll give that a try and see how things come out.

Bob Pownall

Re: Optical fiber with cladding < 125um? (Either buy or make)

On Sun, 02 Apr 2006 16:01:01 -0600, Bob Pownall

Quoted text here. Click to load it

Your best bet is probably the companies that make fiber bundles.  They
use fibers that have very thin claddings so that the packing ratio in
the bundle is high.  

Some companies are Fiberoptix, FiberTech, FiberOptic Systems Inc,
Schott Fiber Optics, Romack Fiber Optics, etc.

For example, FiberTech
(http://www.fibertech.de/pspec_03.htm?PHPSESSID=f6bc5c54bf953002197fba1d63ec07cf )
sells the following two fibers:

AS46/50UVPI-  46um core,  50um clad
AS64/70UVPI-  64um core,  70um clad

I have purchased bundles from FiberOptic Systems Inc that have cores
as small as 25 um, with claddings approx 30 um diameter.

See if you can get them to sell you just the fiber, not in assembled
bundle format.


Re: Optical fiber with cladding < 125um? (Either buy or make)

Anthony Cook wrote:
<Summary: Some suggestions about how to solve my problem.

Thanks Anthony - I'll contact some of the companies you've suggested.

Bob Pownall

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