How to calculate attenuation for optical fiber bundle?

[Inneedofhelp]

Hi,

If I understood it correctly, the coefficient of attenuation for a single optical fiber, is alpha = (10/L)*log(P(0)/P(L)). Assuming if I knew the properties of the optical fiber and the amount of optical fiber in the bundle, then the total attenuation for the bundle is approximately number of optical fiber * attenuation per single fiber? If so, wouldn't single optical fiber be more efficient than optical fiber bundles?

Thanks

 

[berkeman]

then the total attenuation for the bundle is approximately number of optical fiber * attenuation per single fiber?

No, why would you think that is the case? Each fiber is independent -- it's not like they are connected in series...

 

[Inneedofhelp]

Then is there a general equation or estimation that determines the effect of optical fiber bundles? Like how would the increase of amount of optical fiber affect attenuation factor.

 

[berkeman]

A bundle is just a bunch of individual fibers packaged together, unless you are referring to something else. Can you post a link or a picture of what you are looking at? Thanks.

 

[Inneedofhelp]

I understand it as for image/light you would need a bundle of optical fibers rather than one. Basically I want to know how does increase in the number of optical fibers affect the light being transmitted.

 

[berkeman]

In general, it does not, AFAIK. Are you referring to individually clad fibers as used in a telecommunications cable (first pic below), or the unclad fibers used in simple bundles (2nd pic below)? Again, if you could post links or pictures, that would help us.

https://www.e-driver.net/images/8294005_m.jpg

https://www.especialneeds.com/media...c6a9728ccd/l/e/ledFiberOpticBundle-main_6.jpg

 

[Inneedofhelp]

It is for hysteroscopy. It should be clad, there really isn't a picture of the fiber optics as it is embedded in. Sorry

 

[berkeman]

It is for hysteroscopy. It should be clad, there really isn't a picture of the fiber optics as it is embedded in. Sorry

Oh, you are asking about Endoscopes. They use a coherent FO bundle to transmit the image from the distal (far) end of the cable back up to the eyepiece or camera. The attenuation of the light coming from the distal end to the proximal end is just dependent on the loss of each individual fiber. Is that what you are asking about? Bigger diameter fibers in the coherent bundle would have less light loss in general, but you sacrafice resolution when you make them too big.

http://www.genesis.net.au/~ajs/projects/medical_physics/endoscopes/

• Fibre optic bundles
  Light is guided to the area under investigation by non-coherent fibre optic bundles (bundles where the optical fibres are not lined up at both ends). However, the image must be transmitted back by a coherent fibre optic bundle (a bundle where the optical fibres are lined up at both ends of the fibre so that an image can be transmitted). In order to produce a clear image, the shaft contains up to 10 000 fibres!
  

 

[sophiecentaur]

If you use a bunch of fibres then you would, ideally expect n times the amount of light. But the cut end of the cable needs to be illuminated evenly

 

[Inneedofhelp]

The attenuation of the light coming from the distal end to the proximal end is just dependent on the loss of each individual fiber

Isn't that basically total attenuation = number of fiber * attenuation of each fiber?

Also do you have any links/articles to more information about these endoscopy optical fibers regarding any equations or plots? Couldn't find anything detailed when I google it.

 

[berkeman]

Isn't that basically total attenuation = number of fiber * attenuation of each fiber?

No, absolutely not. Please stop saying that. It is very frustrating for me. I have already explained why that is not the case.

Also do you have any links/articles to more information about these endoscopy optical fibers regarding any equations or plots? Couldn't find anything detailed when I google it.

I will try to search for it tomorrow. What are you doing with endoscopy? What is your level of education so far? What is your level of education and training in optics and fiber optics so far? We try to help folks here as best as we can.

 

[NTL2009]

"bundle" isn't a useful term. It can just mean a group of something together. It's like asking "what is the resistance of a bag of resistors".

What is the configuration, and specific application? Endoscopy, but to transmit the image, or to provide light for the camera? Think in terms of the fibers being in series (end-to-end), so that length is increased, and the same light passing through each. Or in parallel, where length is the same, but total cross-sectional area is increased. If in parallel, is the same light entering each fiber?

 

[Inneedofhelp]

No, absolutely not. Please stop saying that. It is very frustrating for me. I have already explained why that is not the case.I will try to search for it tomorrow. What are you doing with endoscopy? What is your level of education so far? What is your level of education and training in optics and fiber optics so far? We try to help folks here as best as we can.

Going to be second year mechanical engineering student. Interested in the in the medical field and want to learn to more to get a good understanding and hopefully internship. Minimal to no training.

 

[sophiecentaur]

Isn't that basically total attenuation = number of fiber * attenuation of each fiber?

How could that possible be true?
Imagine two water trucks with holes in the bottom, setting out on a journey. At the end of the journey, both will have lost the same proportion of their load. Has one truck has any idea about what's happening in the other truck. Take just one truck and drive it twice as far. What proportion of its load will it have lost buy the end?

Apply a bit of good old common sense to those two questions and then apply your answers to the optical fibre situation.

 

[berkeman]

I will try to search for it tomorrow.

The keyword in such a search is "coherent", since that is the type of bundle you are asking about (that is the key to endoscopy technology). Here is the result of a Google search on Coherent Optical Fiber Bundle:

https://www.google.com/search?q=coherent+optical+fiber+bundle&ie=utf-8&oe=utf-8