Why can't we use opaque object in optical fibres?

In summary, the cladding used in an optical fibre is typically of a lower refractive index to allow for total internal reflection within the core. The use of a mirror-like surface is not feasible due to the fact that opaque materials absorb light instead of reflecting it, and different materials have varying levels of reflectivity at different wavelengths. Additionally, creating a mirror-like surface would be expensive and not as efficient as total internal reflection. While metal waveguides can reflect waves like a mirror, they do not utilize total internal reflection and result in significant loss over longer distances.
  • #1
esha
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in an optical fibre the cladding used is ussually of a lesser refractive index so that total internal reflection occurs inside core. instead of using such a combination why can't we use a mirror like surface? will the use of opaque material partially absorb some amount of light?
 
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  • #2
esha said:
will the use of opaque material partially absorb some amount of light?

I think so. Total internal reflection reflects nearly 100% (99.9+%) of the incident light, while most mirrors reflect perhaps 85-99%.
 
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Likes Jamison Lahman
  • #3
Light is refracted in optic fibers due to the fact that the refractive index of the material (i think silica) is closer to that of vacuum and total internal refraction is observed. An opaque object will absorb all incoming light and will only give out luminosity. Thus opaque objects will not show total internal refraction (in fact no refraction at all).
P.S. I might be wrong.
 
  • #4
PlancksApprentice said:
total internal refraction is observed

It's total internal reflection, not refraction. :smile:

PlancksApprentice said:
An opaque object will absorb all incoming light and will only give out luminosity. Thus opaque objects will not show total internal refraction (in fact no refraction at all).

The OP is asking about reflection off of the reflective surface of an opaque object.
 
  • #5
Drakkith said:
It's total internal reflection, not refraction. :smile:
The OP is asking about reflection off of the reflective surface of an opaque object.
Ahhhh. Sorry.
 
  • #6
I thought that a metal waveguide worked perfectly well in the way described, with mirror walls.
 
  • #7
esha said:
why can't we use a mirror like surface?
It may also have to do with the fact that different materials become more or less reflective at various wavelengths.
 
  • #8
In addition to the efficiency arguments presented, I would think creating a mirror-like surface would also be more expensive.
 
  • #9
tech99 said:
I thought that a metal waveguide worked perfectly well in the way described, with mirror walls.

Waveguide walls do not work on TIR. They reflect the waves like a mirror, due to induced currents in a good conductor. A different mechanism, which is far from 100% reflective. You cannot use 100s of meters of waveguide without appreciable loss.
 

1. Why can't we use opaque objects in optical fibers?

Optical fibers are designed to transmit light signals over long distances with minimal loss. Opaque objects, by definition, do not allow light to pass through them. Therefore, using opaque objects in optical fibers would prevent the transmission of light signals, making them ineffective for their intended purpose.

2. Can't we just make the optical fibers larger to accommodate opaque objects?

Increasing the size of optical fibers would defeat the purpose of using them in the first place. The smaller the fiber, the more light can be transmitted with minimal loss. Enlarging the fibers to accommodate opaque objects would result in a significant decrease in the efficiency and effectiveness of the optical fibers.

3. Are there any exceptions where opaque objects can be used in optical fibers?

In some cases, specialized fibers called multi-mode fibers can transmit light through opaque objects such as plastic or metal. However, these fibers are not suitable for long-distance transmission and are typically used for shorter distances in industrial applications.

4. What happens if an opaque object is accidentally placed inside an optical fiber?

If an opaque object is introduced into an optical fiber, it will block the transmission of light signals and disrupt the entire system. This can lead to significant data loss and require extensive repairs to fix the issue.

5. Is there any advantage to using opaque objects in optical fibers?

No, there is no advantage to using opaque objects in optical fibers. The purpose of optical fibers is to transmit light signals, and opaque objects would hinder this process. Other materials, such as copper wires, are more suitable for transmitting signals that do not require the use of light.

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