Question

In: Physics

Refractive index of core of an optical fibre is 1.46 and its diameter is 250μm. Light...

Refractive index of core of an optical fibre is 1.46 and its diameter is 250μm. Light propagates along the axis of the fibre . If the fibre bends at one point with radius of curvature R, Calculate the minimum value (critical radius of curvature R_min) to sustain the light inside, without escaping from the fibre.

Discuss the factors on which the critical radius of curvature may depend? Does it depend on the colour of light propagating through the fibre?

unable to paste diagram.

Expert Solution

The answer is not so straightforward because some details are missing.

OBS:

- The index of refraction of the cladding rather than that of the air should be considered when writing the Snell's law.

- Which type of fiber is this one? Multimode, singlemode?

- I suppose it's about macrobending.

A formula for ray curvature is given only in the case of multimode fiber. For singlemode there is another criterion. Approach I:

n1=index of the core

n2=index of the cladding

R_min depends on the wavelength of the light traveling through the fiber.

Anyway, even if considering the outer medium the air and not the cladding, the value for R cannot be calculated numerically because we don't know the wavelength.

Approach II:

Minimum bend radius for a cable is typically 10 to 20 times the outer diameter of the cable. In Cabling Standards the common value is 15 times the cable diameter. If considering this practical info we have in this case: R_min=3.75 mm.

No wavelength dependence in this case.

I cannot say more.

genius_generous answered 1 week ago

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