| Author | Message | ||
     David W. Hopkins (dhopkins) Senior Member Username: dhopkins Post Number: 227 Registered: 10-2002 |
Thanks, Howard. That link is nice! | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 525 Registered: 9-2001 |
Dave - if you select the type of fiber, and enter the length you're interested in, the blank charts will be filled in with the curves for the specific conditions you selected. \o/ /_\ | ||
| David W. Hopkins (dhopkins) Senior Member Username: dhopkins Post Number: 226 Registered: 10-2002 |
Hi Alisha, Thanks for sharing this. It was not clear to me that you were asking for technical details that would allow you to calculate lengths that might be reachable. The first 2 charts, labelled Transmission curves, do not seem to have any plots on them. Is this what you saw too, or has something happened in the uploading of the plots? I found the attenuation curves for the various fiber types very interesting. It was surprising that below about 450 nm, even the best, low OH fiber most useful in the VIS-IR is not useful in the UV. Tomas may have used yet another fiber type for his UV work. I wonder if the upward slope in the 150-300 nm region is due to fine bubbles or other inclusions in the glass? The sharp bands are all due to absorption by the occasional -SiOH- groups formed in the structure of the glass from the many -SiO- groups, I think. It is very significant that the 1900 nm band seen in water and ice and appears in many grains at about 1940 nm is hardly observed in the fibers. That band is due to the combination bands of -OH in water. Makes sense. Best regards, Dave | ||
| Alisha (agnosus) Advanced Member Username: agnosus Post Number: 21 Registered: 1-2009 |
Thanks! A colleague in Bruker directed me to this weblink: http://www.leoni-fiber-optics.com/Transmission-Tool.11883.0.html Just what I wanted! Alisha | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 523 Registered: 9-2001 |
Dave - why tell me? You need to notify whoever committed such a dastardly offence against a prominent scientist!! :-) \o/ /_\ | ||
| David W. Hopkins (dhopkins) Senior Member Username: dhopkins Post Number: 225 Registered: 10-2002 |
Hi Howard, Good job! Tomas was an amazing scientist. I certainly feel fortunate to have worked with him on the ASTM Committee on NIR methods. By the way, I noticed that his name was spelled with the "sch". It seems to me that recent communications regarding the Tomas Hirschfeld Award from ICNIRS used "sh". Best regards, Dave | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 522 Registered: 9-2001 |
Well, here's one, Tony: http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1222524 \o/ /_\ | ||
| Tony Davies (td) Moderator Username: td Post Number: 295 Registered: 1-2001 |
Hi Alisha, et al., I have a distant memory of some work done at BP (in the UK) when they made NIR measurements using a 1 kilometer length fibre!! I cannot remember any details except (obviously) it was a very special fibre. I haven't thought of the correct question to ask the internet, over to you Howard Best wishes, Tony | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 519 Registered: 9-2001 |
Alisha - BTW: the late Tomas Hirschfeld used to enjoy doing unusual things with fibers while he was working at Lawrence Livermore Labs. One of the things he used to talk about at conferences was to run fibers between buildings at the lab, in order to extend the distances he could claim as a record. I'm sure he exceeded 200 meters but I don't know of any documentation. On the other hand, the Internet knows EVERYTHING - - - as long as you can figure out the right question to ask! \o/ /_\ | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 518 Registered: 9-2001 |
Alisha - Gabi is correct, "ordinary" low-OH fiber for NIR use still contains a residue of -OH. But once, when the use of low-OH optical fiber for analytical use in the NIR was still in its infancy, a representative from Corning Glass gave a talk at Pittcon describing optical fibers made from a special research batch of glass that had No -OH. He compared it with the ordinary low-OH fibers, and it was impressive. I don't know if Corning still makes that type of fiber, but you might want to contact them about it, to see if it is still available. \o/ /_\ | ||
| Gabi Levin (gabiruth) Senior Member Username: gabiruth Post Number: 83 Registered: 5-2009 |
Dear Alisha, The maximum useful length of fiber depends also on the application. Even best fibers have attenuation - which is of course length dependent. Even best fibers still contain some O-H bonds - which of course contribute to loss of signal in the typical regions. I have observed this phenomenon even with fibers 60 meters long. The longest fiber we have ever installed was about 130 meters each way. There is also a question of economical consideration. Depending on the price you pay per meter, if you go 200 meters, it is 400 meters of fiber. There is also the cost of placing all the conduits, and getting the fibers through the whole length - which will add up the longer you go. It is possible to "remove" the O-H signature from the spectrum by using background correction, but you can't prevent the loss of signal, so at the end of the day - the quality of spectrum is reduced the larger the signal loss. Therefore, if at 200 meters your set up gives you a good signal which contains the desired information clearly and with good signal to noise ratio - you can go to 200 meters. The other issue with 200 meter fibre of 600 micron diameter is - getting it to go through all the conduits with the bends and turns - it is a long way - without breaking it in the process. If you can do that, and the quality of signal is still OK for your application - go ahead with it. Gabi Levin Brimrose | ||
| Peter Tillmann (tillmann) Senior Member Username: tillmann Post Number: 31 Registered: 11-2001 |
sorry, our longest one in use is only 120 m (each way, to probe and back). Peter | ||
| iyas (iyas) Senior Member Username: iyas Post Number: 34 Registered: 7-2007 |
I think the normal length used is 1.5- 3 meters One device I have heard about it , the length of the fiber was 15 meters but I am not sure if there is a fiber of 200 meters long .. it would be great and very expensive I think Iyas | ||
| Alisha (agnosus) Intermediate Member Username: agnosus Post Number: 20 Registered: 1-2009 |
Dear All, I wonder if anybody here knows what was the maximum fibre length ever used for an NIR application? I will appreciate if you can share any spactra / transmission profile for very long fibre lengths (>200 m)? Thanks, Alisha |