I am curious to know how exactly does the fiber optics works. I understand the basic concepts of the fiber optics communications but am curious to know if there is a way to send multiple signals in same core at the same time in the fiber optics? How is it possible? Is there a way you can send light of different wavelength and able to detect them at the rx end?
122101
Can optical fibers transmit in both directions simultaneously? Both single mode fibers and multi mode? What about if they we choose non-interfering wavelengths?
105833
I recently watched  by Veritasium where he talks about the One Way Speed of Light and talks about the limiting case where in one direction the speed of light is $c/2$ while it's instantaneous in the other. He also says this is perfectly fine according to our Physics theories. He also points at Einstein's assumption in his famous 1905 paper where he assumes that the speed of light is same in all directions. This made me ask this question is taking the speed of light same in all directions an axiom of some sort? As I've often read no information can be sent at more than the speed of light but here one-way taking the speed to infinite makes no difference. So are all of our physics theories based on the assumption and what would happen if light turns out to be moving at different speeds in different direction? Will that enable transfer of information faster than the speed of light and is there any way for us knowing that the transfer happens faster than the speed of light? The video takes a Earth Mars case where he says it isn't possible for us to every realize this discrepancy but is there a more general proof which says it isn't possible
103093
As the photo shows, the pins are wired "straight across", rather than diagonally. This means that it does not work as an Ethernet/8P8C coupler because the transmit pins are  (for 10/100 Mbit/s at least). Likewise, it doesn't act as a crossover either.  Is it wired wrong? Or is it a special form of a 1000Base-T crossover? Or is it perhaps used to correct the pins from another reversed device...?
30549
If just a single photon hit a single slit interferometer, what would happen? Would you just see a dot on the screen, or would there be a diffraction pattern? Furthermore, if you had a double slit interferometer but also had which-path information would there still be a diffraction pattern even though there is no interference?
13207
I was wondering (since I've looked pretty hard and haven't been able to find anything)-  are there any models that explain the polarization of light upon reflection? Everywhere I've looked I've seen things like the Brewster angle mentioned, and empirical data, but I haven't yet found any theoretical models that explain this type of polarization. Can anybody point me in the right direction? Or have no such models been made?
7219
It is well known that a  can "split light" by separating different frequencies of light:    Many sources state that the reason this happens is that the  is different for different frequencies.  This is known as .  My question is about why dispersion exists.  Is frequency dependence for refraction a property fundamental to all waves?  Is the effect the result of some sort of non-linearity in response by the refracting material to electromagnetic fields?  Are there (theoretically) any materials that have an essentially constant, non-unity index of refraction (at least for the visible spectrum)?
123568
I have some understanding of what frequency modulation entails - it entails "adding" a new frequency to the frequency spectrum of a signal. But how, exactly, is a modulated signal selected in the receiver? Say you're listening to your car radio and want the radio signal modulated at 80 Hz or something. How does the actual system select it? In general, not in car radios specifically.
30334
Does there exist a laser that is tunable over the whole visible spectrum? If so does there exist one that is solid state? This is to settle a score with my dumb workmates.
5281
The book I'm reading about optics says at some point that "each color (wavelength) contained in the white light interferes only with itself". But why is this so?  Edit: I moved the rest of the question .
30326
My book of physics (I don't quote it here, since it is in Catalan) says  that in the 1887 Michelson - Morley experiment, after getting the transversal and longitudinal phase shifts, they claim that the number of fringer observed will belong to the number of times that both phase shifts contains 2 pi because that is the phase two maximums  repeat. My question is: why is here said that waves should form maximums? Because as I understand it, the expected result was to obtain a destructive interference whose phase shift could be jsed to determine Earth's velocity. If they were expecting a destructive interference, shouldn't the book use the phase two minimums repeat?
110992
Pardon me if this has been asked before. I was just thinking about how light from a source like the sun is unpolarized. I have two questions:   Is unpolarized light from the sun 100% random? Meaning all wavelengths in the visible spectrum, polarized in all directions? (please correct me if "polarized" is not the right term here) If that's the case, how do the random waves not cancel each other out, rendering the sun invisible to us when we look at it?   Of course my thinking is flawed, so I'm just wondering what I'm missing. The analogy I could come up with is that waves in the ocean are random (I assume?), yet they still occur. Thanks in advance to anyone who can fix my brain.
19693
What's the smallest aperture a photon can pass through? I mean with no transmission at all.  I'm pretty sure I saw long ago an experiment when they were reducing the size of a hole in a gold film and at about a quarter or a third of the wavelength there was no transmission.   If so, can we say that the size of the aperture can be associated with the dimension of the photon?
2134
Yesterday I read that we can affect the path and the 'form' (particle or wave) of a photon after the fact ().  Part of what is puzzling me is the beam-splitter. Are the individual photons actually being split into two new photons of lesser energy?  This  implies that you cannot split a photon but it seems that beam splitters do exactly that.
3096
If we have 2 beams of light with equal intensities, but with different frequencies, wouldn't the one with the higher frequency generate more power?  If so, how come the intensity, which is in $W/m^2$, of the higher frequency beam is not higher?
23265
Suppose I have two counter-propagating travelling waves of the same frequency but of different amplitude, like the transverse waves produced in a string by partial reflection off an endpoint.  I read that we will get a mixture of standing and traveling waves, and I can see the theoretical part, but what does this mean, exactly? What are the nodes now? Also, can I now say that energy between loops will be non-transmitting? Because now we have both a traveling and a standing wave.  If possible please provide a picture for better visualization.
13076
I'm confused, does the absorption and emission determine the color of something? Or does that only happen when something is emitting energy?  When light hits an object, the photons get absorbed, then emitted with a different wavelength right?
73509
I've tried to search for this answer but found no proper explanation.  My previous ideas were...  1) It is not a point source, so the different points on a filament lamp may cancel out the light from other points on a filament lamp  2) It emits light rays at random (even though I've read this, I don't exactly understand what it means. Does it mean a single point on the filament may emit a photon one second and then the next second not emit anything?)  Are these reasons along the right lines? Could someone give a proper explanation as to why a filament lamp is an incoherent light source?