Multimode optical fiber, physics beginner help :D

[sophiecentaur]

I just wonder what I'm doing wrong then.

What you are doing wrong is refusing to read what's written because it's not what you have been thinking. The phase of a wave depends on how far from the source you are looking. To different sources in two different places will be shifted by different amounts except on the centre line. It's their relative phases that govern the result.
If you are still not getting it then use Google and read several different sources. The Hyperphysics site is pretty good for most basic Physics - but you have to READ what it says (the details). You have to open your mind for this. No one can do that for you.

 

[sophiecentaur]

Peaks lines up with peaks and that increases the amplitude or decreases the amplitude.

That is not what has been said! Read!

 

[Xenon02]

The phase of a wave depends on how far from the source you are looking. To different sources in two different places will be shifted by different amounts except on the centre line. It's their relative phases that govern the result.

This is the phase difference that you mentioned ?

This in red and in pink (I guess this is pink). This is what you mentioned about wave phases ?

 

[sophiecentaur]

Just get some reading on the topic. You are the one who’s out of step, as I have implied.

 

[Xenon02]

Just get some reading on the topic. You are the one who’s out of step, as I have implied.

@sophiecentaur
I mean I just got confused.
Many stuff just mixed up in my head and I don't know where to start again.
In the topic there is also everything a bit mixed. Or maybe I read it wrongly some comments.

How light works maybe easy but I just get confused of overflowed information I got from school.
I just think of the phases of the waves that spread all around. Also I think about what happens when there are more sources of light in the multifibre.

As you mentioned I might think wrong but I'm trying to get conclusion out of it. And I'm trying to use pictures and draw on them to show what does it mean to me what I read.
Also I tried to find something why what works but as I said new stuff just mixes with the old ones and even the old ones gets complicated.

Sorry.

 

[Xenon02]

@sophiecentaur

Okey I've read some comments + this article Khanacademy link. Just like you said. I tried to understand it again, but I don't know if what I will say now is correct. I'll use some picture for it.
I'll try to explain some stuff of what did I understand. If you could if it's okey or Correct/Incorrect (sorry again for the problem).
I'm slowly getting it I guess.
So basically when I have two wavelengths that are connected to each other fully then it depends what happens. If the second wavelengths is in phase with the first then it is constructive interference, if the second one is shiftd 180 degree then it is Destructive.

I didn't understand the moment when it was written that it's leading to a new wave. Like creating ?
Maybe I'm wrong but I remember that when they meet each other at certain point then this point is constructive and when waves exit this place then it comes back to normal (maybe I am wrong).
Also about the phase shifts this one is also interesting : Phase shift

About the shifts I've watched some videos and read about how it actually works. I've seen the simulation that showed how it looks like for 2 slits which was also interesting.

Here it looks like it is now how to call it max constructive interference nor max destructive interference. Something between. And that's how it actually works I guess.
But what was disturbing me was how it was called this difference. In the article it was said that it is Path difference. On the video it was wavelength difference.
Usually when I hear wavelength difference I imagine something like this :

Like one is slower and one is faster that is certainly a wavelength difference. But there (for interference) it had a different meaning, or I just didn't understand it fully. It was the path that made the wave delay and it looked like it was shifted.

Something like that ?

 

[hutchphd]

For the multimode/singlemode fiber discussion the most important piece is the path length difference. The single mode fiber greatly diminishes the possibility of alternate paths for any given signal. So the result is much "cleaner" at the end.

 

[berkeman]

Thread closed for Moderation...

For the multimode/singlemode fiber discussion the most important piece is the path length difference. The single mode fiber greatly diminishes the possibility of alternate paths for any given signal. So the result is much "cleaner" at the end.

Exactly, which was the main question in the OP. But there was all kinds of other stuff about coherent interference and multi-wavelength interactions and so on, which has made this thread too muddled for me to be able to follow. I'll try to sort it out in the next couple of days, and maybe have the OP start a new thread on what they really want to ask. Lordy.

UPDATE -- I am discussing the issues with the OP in a PM.