Optical Fibres - A Level Physics

This video explains how optical fibres (or optical fibers if you're American) work for A Level Physics.
Optical fibres use total internal reflection in order to send information. A light signal is sent down an optical fibre which can be received quite a distance away. The signal isn't perfect because different light rays travel different distances - this is called modal dispersion. The signal is put through a filter in order to get the original signal back out.
Thanks for watching,
Lewis
This video is recommended for anyone studying A Level Physics in the following exam boards:
AQA
CIE
Edexcel (don't need to know details)
Edexcel IAL
Eduqas
IB
OCR A
OCR B
WJEC
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[@SakSakSakit]

Thanks a ton! I have my AS Physics exam next week, I should have found you earlier!!!

[@BionicSynth]

I know this is two years later but what exam board did you sit?

[@murtazaahmed2502]

Best teacher ever helping in lockdown and you make me think physics is easy 😉😁

[@charworrior]

Your videos are always so good! Youve helped me alot!

[@PhysicsOnline]

Thanks

[@the_hasnat]

0:50 "provided that the critical angle isn't exceeded" Shouldn't it be "provided that the critical angle IS exceeded"

[@milliehenshaw9113]

thought that too

[@alisterdavid5109]

yeh was about to comment that, I think you're right

[@nope-jh6nx]

I agree

[@VonDutchyy]

0.50 , you say "as long as the critical angle inst exceed, the ray of light will continue to travel along", surely the angle must be exceeded each and every time it bounces to reach the end?

[@PhysicsOnline]

+Salty Korean Kid You're right - I just made a mistake as I was speaking. Thanks.

[@VonDutchyy]

+A Level Physics Online no worries, just that I have my exam tomorrow and got a bit panicky

[@RAAAHUM]

Thanks for this video, and sorry to be a bother but u havent talked about material dispersion which I didnt quite understand in class, so I was hoping u could explain it to me.

[@MsFlubbub]

Very good and helpful videos, thank you

[@Tom-ix9dt]

any chance you will do converging and divering lenses?

[@TheAlmostKingOfPotatoes]

Damn, i was hoping you would talk about how the cladding has a different refractive index and how this helps with the light not refracting but instead reflecting. also about the critical angle and its effect..

[@naomiburrows9124]

The cladding has a lower refractive index than the core to ensure that the light totally internally reflects. Something can't totally internally reflect if the outside has a higher refractive index - if you want to prove this to yourself, try using the critical angle equation for something traveling from air into glass with a refractive index of, say, 1.3 (sinθc=n2/n1 , where n1=the refractive index of of the thing you're in (glass) and n2=the refractive index of the thing on the outside (air)). If you try to put it into your calculator, you'll get some form of error message. This is because sinθ only exists between -1 and 1. 1.3/1 >1 so there is no critical angle; TIR can't happen. The actual PURPOSE of the cladding is not so much to make the light totally internally reflect - air would have a lower refractive index than the core anyway so the light would still undergo TIR without any cladding at all! Its purpose is to prevent crossover (if you had a bunch of optical fibre cores together with no cladding to separate them, the signal would just 'jump' between the cables and make a massive mess) and also to prevent damage to the core -- scratches could cause the angle of incidence to be less than the critical angle so the light would escape. Hope this helps :)

[@WarriorOfAllah3]

Hello,For AQA, don’t we also need to learn about material dispersion, pulse broadening and absorption. That is what I read on their specification and was hoping you would go through.

[@PhysicsOnline]

iAmMuslim You do, but I haven’t made a video in that yet. I’ll add it to my list.

[@WarriorOfAllah3]

A Level Physics Online Oh ok. Thank you for the clarification.

[@TheSurrealTV]

Do we need to know optical fibres for the new OCR spec?

[@mattwhitelock4725]

Check the specification - I don't think we do, for OCR B at least (you might be on OCR A)

[@Josephlegoman23]

Do we need to know this for OCR A because it doesn't appear on the spec, however there are past paper questions on it so i'm a little confused? Great videos though, thank you!

[@calteckk]

what is material dispersion

[@sambowater3972]

Isnt n1 the medium you are in and trying to leave and n2 the medium you are trying to enter so those are the wrong way round

[@secretlyanonymous2365]

Optical fibres arent on the G482 checklist? Is this something we need to know for ocr?

[@PhysicsOnline]

Not for OCR G482

[@the_hasnat]

safe bro.

[@leonardodavinci9814]

Why is the refractive power of the outer layer of the fiber smaller? That means that light passes through inside the fiber in a slower velocity than outside it. Why cant it be inverted? For example Refractive power is smaller: n=3.10^8/8 Refractive power is bigger: n=3.10^8/4 Refractive power is bigger that means that light passes through that material slower. Why does it happen INSIDE the optical fiber? Thanks

[@dallah1233]

Ž

[@thibbledibble]

That's not a zoomed in view of an optical fibre its a drawing

[@krypton1142]

shut up