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

[esha]

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?

 

[Drakkith]

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%.

 

[PlancksApprentice]

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.

 

[Drakkith]

total internal refraction is observed

It's total internal reflection, not refraction.

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.

 

[PlancksApprentice]

It's total internal reflection, not refraction.
The OP is asking about reflection off of the reflective surface of an opaque object.

Ahhhh. Sorry.

 

[tech99]

I thought that a metal waveguide worked perfectly well in the way described, with mirror walls.

 

[Jamison Lahman]

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.

 

[pixel]

In addition to the efficiency arguments presented, I would think creating a mirror-like surface would also be more expensive.

 

[sophiecentaur]

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.