Exploring the Relationship Between Pulse Shape and Spectrum in Dispersive Media

[eahaidar]

I want to ask how does the wave keep the same amplitude if the wave broadens ?
Thank you for your time

 

[Simon Bridge]

The periodicity of the waves means that as the different frequency waves spread out, they will still add up to the same wave shape. But for a pulse, the amplitude does change.
http://www.acs.psu.edu/drussell/Demos/Dispersion/dispersion.html

 

[eahaidar]

The periodicity of the waves means that as the different frequency waves spread out, they will still add up to the same wave shape. But for a pulse, the amplitude does change.
http://www.acs.psu.edu/drussell/Demos/Dispersion/dispersion.html

Thank u I was watching a lecture about self modulation and dispersion I just having a hard time understanding what do they mean when they say pulse shape changes while the spectrum remains the same with distance and vice versa can u elaborate on that ?
Thank you so much

 

[Simon Bridge]

The pulse is made of traveling sine waves.
The particular mix of sine waves that go to make the pulse is it's spectrum.

In a dispersive media, the different sine waves travel at different speeds - making the pulse change shape - but the mixture is still the same because the individual sine waves go through all space.

But I'd have to see the comment in context to figure what they mean.

The vice versa of "the pulse shape changes while the spectrum stays the same" would be

"the spectrum changes while the pulse shape stays the same"

... for the pulse shape to stay the same, in a dispersive media, the spectrum must change.

 

[eahaidar]

The pulse is made of traveling sine waves.
The particular mix of sine waves that go to make the pulse is it's spectrum.

In a dispersive media, the different sine waves travel at different speeds - making the pulse change shape - but the mixture is still the same because the individual sine waves go through all space.

But I'd have to see the comment in context to figure what they mean.

The vice versa of "the pulse shape changes while the spectrum stays the same" would be

"the spectrum changes while the pulse shape stays the same"

... for the pulse shape to stay the same, in a dispersive media, the spectrum must change.

You are amazing man I really want to thank you so in SPM the spectrum changes while the time pulse stays the same means. That the even though the summation of the pulses is changing the pulses traveling would stay the same?
Thank you so much I hope I understood u correctly