Number of modes in optical fiber

AI Thread Summary
A single mode fiber can potentially exhibit multimode behavior if a shorter wavelength light, such as 633nm from a HeNe laser, is used instead of its designed operational wavelength of 1300nm. The calculation suggests that using 633nm could result in approximately two modes. However, the observed non-uniform mode pattern may indicate that the fiber in question is actually multimode rather than single mode. This discrepancy raises questions about the fiber's specifications and intended use. Ultimately, the characteristics of the fiber and the wavelength used play crucial roles in determining the mode behavior.
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Homework Statement


Can a single mode fiber become multimode if the wavelength of the light passed through it is small enough?

I put a HeNe laser (633nm) through what I thought was a single mode fiber. If it's supposed to operate at 1300nm, then would a low wavelength of 633nm cause multiple modes in the single mode fiber?

Homework Equations


number of modes = operational wavelength / wavelength used

The Attempt at a Solution


number of modes = 1300nm/633nm = (approx.) 2 modes?

I'm not sure why my image isn't showing a uniform mode / pattern.
 

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says said:

Homework Statement


Can a single mode fiber become multimode if the wavelength of the light passed through it is small enough?

I put a HeNe laser (633nm) through what I thought was a single mode fiber. If it's supposed to operate at 1300nm, then would a low wavelength of 633nm cause multiple modes in the single mode fiber?

Homework Equations


number of modes = operational wavelength / wavelength used

The Attempt at a Solution


number of modes = 1300nm/633nm = (approx.) 2 modes?

I'm not sure why my image isn't showing a uniform mode / pattern.
Maybe you have a multimode fibre?
 
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