# Transmission in Single Mode Waveguide

• I
Hello there,

I was wondering if the power profile of a single mode waveguide can be changed? I mean, a wave that travels through the waveguide will have a harmonic shape, right? Is it possible to get a different shape of the power profile?

Thank you :)

Related Other Physics Topics News on Phys.org
tech99
Gold Member
Hello there,

I was wondering if the power profile of a single mode waveguide can be changed? I mean, a wave that travels through the waveguide will have a harmonic shape, right? Is it possible to get a different shape of the power profile?

Thank you :)
The cross sectional shape of the 'guide can be changed, for instance, to a dumb bell, or from round to rectangular. The walls can be loaded with dielectric, or by inserting screws. But essentially, a waveguide guides a wave, and its contents will be wave-like!

sophiecentaur
Gold Member
I was wondering if the power profile of a single mode waveguide can be changed?
What exactly do you mean by "power profile'?
Is there some reference you can give us to help get some context here?

Thank you for your replies. Well, when I simulate a waveguide, I can look at the input over the output profile. Does that make sense?

sophiecentaur
Gold Member
the output profile
Do you mean the Field distribution over the end? Do we have a translation problem here?

So, the field distribution would be a cross section of the waveguide, right? What I meant with the "output profile" was more like the Power Profile. So the question is: can I have a power profile of a single mode waveguide that is for example rectangular shaped?

davenn
Gold Member
2019 Award
So, the field distribution would be a cross section of the waveguide, right? What I meant with the "output profile" was more like the Power Profile. So the question is: can I have a power profile of a single mode waveguide that is for example rectangular shaped?
your term power profile still doesn't really make sense
do you understand how the electric and magnetic fields look inside a waveguide ?

have you seen these diagrams before ? ......

..

Thank you for your reply, daevnn. Sorry, I might have labelled it wrong. It is probably a basics problem. Yes, I have seen these before. I think I understand how the waves propagate. What I tried to say is: when I "cut" the waveguide (like a cross section), I will get a sinusoidal function for the E-field for example. Because this is how the waves propagate, just like in the pictures you send. But if I simulate a device, I can also plot the input-output profile of this device, which is like the spectral response, right?

So, if I for example have a single mode waveguide coming into a multimode wavguide this will create an interference pattern and self-imaging, right? At some points, I will get an overlap of two images, which creates a "rectangular" shape of the crosssection, instead of a sinusoidal function (because it is two sinusoidal functions overlapping and creating a broader, flattened function). Can I transfer this flat image into a single mode waveguide if I put a single mode waveguide behind the multimode waveguide?

davenn
Gold Member
2019 Award
But if I simulate a device, I can also plot the input-output profile of this device,
when you say device, are you referring to the waveguide or something else ?

which is like the spectral response, right?
The waveguide, like all RF components has a frequency response. That is you can plot how it responds to a change in applied frequency

Waveguide is basically a high pass filter. It will only pass frequencies above a certain frequency ( for a given size waveguide)
that lower frequency is called the cutoff frequency.
A note to be made .... although the WG will pass all higher frequencies, above a certain point multi-moding will occur and this will
lead to losses ( greater attenuation) of the signal.
As a result, WG has a stated lower freq of use ( the cutoff frequency) and a high end freq limit before which moding occurs

Dave

sophiecentaur