Spectrum of High-OH Fiber from 1.5 to 1.7 Microns

In the early days of fiber optics for communications, it was found that the transmission was poor at certain wavelengths. It was soon found that the cause was trace amounts of water in the fibers. The 1.55 to 1.7 micron range includes the first overtone of the O-H stretching vibration.

Hi Marvin --

Thanks for the reply.

I understand that fiber attenuates fairly strongly for telecomms applications. My application is for a sensor however. I don't need to transmit data for kilometers; I need to transmit only 2 meters. I'm currious if I can get 90% transmission or so out of a 2 meter standard high-OH fiber.

Also, as I understand, the primary OH absorption should occur at 1.4 micrometer. I think there should be somewhat of a window between the 1.4 micron overtone and the 2.8 fundamental OH absorptions. I suspect that the wings of the two absorptions might overlap so that the attenuation would be higher than usable for telecoms but maybe not for a sensor.

S>> Can someone point me to a spectrum for high-OH silica-silica fiber at

You are right, but I don't have specifics for particular fibers. The makers might not bother to make measurements in that wavelength range. Perhaps you can get samples?

Water has bbsorption lines at 1.2, 1.4, 1.9 and 2.4 µm (out of my memories). The attenuation at 1.6 is of the order of 1db/Km, at i.4 of 3 db/Km (this comes from a very old booklet of AMP. The attenuation increases sharply when moving towards IR. I would say that the wavelength you need will be a critical parameter to decide if you can use a high OH fiber.

Keep in mind that OH bands are sensitive to the temperature with considerable wavelengths shifts. So, for a sensor application where the signal stability is an important parameter I would stick to low OH fibers independently from the attenuation.

Cheers, Alessandro

Allesandro,

Use a special fibers:

Typical curve for a fiber: What is your application?

Best Regards Urs

It was John asking :-). I made years ago a NIE analyser for ethanol in wine using low OH fibres for the reasons I told

John, see my other mail for the infos - what is your application? Urs

Hi Urs

What I'm really looking for is a fused fiber splitter made from a low-OH, high NA fiber with a 200 micron or larger core.

So far I haven't been able to turn one up. I've found some high NA fiber in low-OH. I haven't found a fused fiber splitter vendor that uses it.

I have found a splitter vendor that has an off-the-shelf device that uses

200 micron core fiber... but the fiber is high-OH. I figure that I can withstand 100 dB/km of attenuation but I'm a bit worried about the stability. Also, no one has actual published fiber spectra on high-OH fiber in that wavelength range any longer since it is no good for any significant distance.

My application is for a chemical sensor. Spectroscopic signatures are in the 1550 to 1700 nm range. Unfortunately, I need to be opaque in my description.

Any thoughts on vendors that have a suitable splitter? My application is worth approximately 1000 pcs per year so I could possibly use a semi-custom splitter.

Sincerely,

John

I think it is difficult to find this component? Could you think to a bundle with a small number of fibers (2-6)? For my thesis work I used 2 fibers tightly packed so that there was a large overlap of the illuminated areas and it worked. This company offer some ready-made solutions

but the bundles are with 6-7 fibers.

Also, I found very cooperative people at

maybe you can check if they can manufacture the splitter according your specifications.

Good luck, Alessandro

Only reason I know them is that I met the founder at one SPIE conference years ago. He's a russian that left the country at the beginning of the

90s and started the company in Germany. They are reasonably priced. There are other companies producing the same kind of things, but they are tipically more expensive, but maybe you could check with Ocean Optics and modify one of their probes.

But please, do not forget to post the results of your search or send me the name of the vendor you select at delbianco AT ipac DOT at. The information on who is producing these components is always precious to have.