Optical Fiber Bundle

Try Industrial Fiber Optics in Phoenix, AZ.

If you need a imaging bundle, that may be a hard target to meet.

Steve R.

Thanks Steve. Yes, I've tried them.

No imaging required. This is for an absorption measurement through a diffusing material.

I saw a 3 mm diameter bundle of 40 um glass with the needed NA at a customer site, but they had no idea of the original source of the fibers. I've tried to find the source, but there's so much noise on the net about optical fibers and this is such a specialized setup that I've had no success.

Why do you need such small fibres? Slightly bigger ones with 0.4 NA are available for box tops.

Cheers

Phil Hobbs

If Thorlabs does not have it, if IFO does not have it, and these folks do not know about it, it probably does not exist.

Are you sure it its not 400 uM outer diameter? Its amazingly hard to obtain good coupling to a 40 uM core. 40 uM core is not what I'd expect in a light gathering implementation.

Call Ozoptics and ask, I've had good luck with them in the past.

Steve

I wasn't aware of Ozoptics. Thanks for the lead.

ChesterW

Hi Phil,

Thanks for the reply, and thanks also for 'Building Elecrto-Optical Systems', it's been very helpful.

The fibers don't necessarily need to be 40 um diameter. We're doing fNIRS

which is basically IR absorbance spectroscopy through the skull to determine relative concentrations of oxy and de-oxy hemoglobin, changes of which indicate functional activations in the cortex. We measure using an array of emitters/receivers and use tomographic methods to reconstruct images of the cortical activations. Uncertainties in the optical path length limit attainable resolutions to the neighborhood of

The absorption curves of the chromophores drive the IR transmission spec for the receive fibers.

Since the whole transmit/receive setup goes on someone's head, the fibers need to be light and flexible. This drives the specification toward a bundle of small fibers.

Here's an example of a bundle glass fibers. I calipered them at 40 um diameter (caliper resolution is 10 um).

Here's an effort using jacketed 230 um glass fibers. It has good transmission, but is not flexible enough and is a bit large:

And here's an effort using 240 um diameter PMMA fibers. It's fairly flexile, but looses about 3 dB per meter at 850 nm.

So, what I need is a source for unjacketed fibers with less than 1 dB per meter attenuation from 650 to 900 nm and small diameter. Our ideal solution would be 250 um plastic fibers, except for the high IR absorption. Any suggestions would be much appreciated.

ChesterW

Hi, Chester,

Good on you. I'm doing some vaguely similar things in different regimes--transcutaneous blood alcohol and glucose, and haemoglobin detection for finding blood spots in hens' eggs.

I've been using 200/240 um, NA 0.22 to 0.40 fibres in bundles for similar etendue management reasons. They're good medicine in combination with grating spectrometers, because you can bunch the fibres into a disc to match the source or detector, and fan them out into a line to form the spectrometer slit.

Cheers

Phil Hobbs

If you manage to do reliable transcutaneous blood glucose, that would be quite an accomplishment.

Here's something you may find useful. It's a method for a multiplexed optical measurement, a kind of multiplexed lock-in-amplifier scheme.

So, any recommendations for a go-to guy who may be able to steer me to a fiber company that can construct the needed fibers?

ChesterW

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fNIRS

Ah-ha. It begins to sound like you want 100/140 um glass fibers. Good characteristics to 1300 nm or so, reasonable flexibility.

?-)

We have been using this in job interviews with great success,

Simple entered in one ear, inspects if anything is there in the brain area. We usually double check by seeing if light comes out the other ear.

It is also useful for inspecting PCBs.

I've gotten my custom fiber bundles from Oplatek. They do all kinds of bundles and can also draw custom fibers. They sell stuff all overthe world. Contact Juha.Kauppinen at oplatek.com for more information.

We get fibre bundles from Fiber Optic Systems in SoCal. Ask for Todd.

At the moment I'm still writing code for the preproduction glucose and alcohol probe. The engineering house spent the best part of a million bucks of the client's money iterating a bad mechanical design and writing hopelessly buggy Labview code. Not only would they not calculate anything themselves, they wouldn't even heed the calculations I sent them.

They're not a good candidate for repeat business, that's for sure.

The grating motion is nonrepeatable enough that the measurement error is dominated by (delta lambda) * (dA/d lambda), so I'm putting in an independent measurement of the grating position. So far just the code has taken me two weeks, because it has to be bug-for-bug compatible with the firmware (which I can't change).

At least the firmware guy was a lot more talented than the Labview guy, so it's possible to code round the bugs (so far).

Labview and spreadsheets. Both inventions of the devil.

Cheers

Phil Hobbs

Thanks Mikko. I'll give them a call later this week.

ChesterW

That project sounds like a real gem.

Thanks for the fiber lead.

ChesterW

I have quotes for bundles meeting the spec from two different vendors. You guys are the greatest.