# I How to calculate attenuation for optical fiber bundle?

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1. Jul 20, 2017

### 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

2. Jul 20, 2017

### Staff: Mentor

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

3. Jul 20, 2017

### 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.

4. Jul 20, 2017

### Staff: Mentor

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.

5. Jul 20, 2017

### 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.

6. Jul 20, 2017

### Staff: Mentor

7. Jul 20, 2017

### 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

8. Jul 20, 2017

### Staff: Mentor

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/

9. Jul 20, 2017

### 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

10. Jul 20, 2017

### Inneedofhelp

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

11. Jul 20, 2017

### Staff: Mentor

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.

12. Jul 20, 2017

### 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?

13. Jul 21, 2017

### Inneedofhelp

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.

14. Jul 21, 2017

### sophiecentaur

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.

15. Jul 21, 2017