I'm a telecoms engineer that installs fibre and we use red lights to find faults in our telecoms network. The light once shone through can be seen through the fibre at a few kilometers! 👌🏽

I thought the reason why we shouldn't bend the fiber optic cable too much is because the glass inside would snap

I love how this channel brings a sense of whimsy to science. Thank you for your material!

You are the science teacher that I needed in high school. Love your videos!

You’ve taught me so much physics and inspired me to take a physics class over the summer which has expanded my knowledge so much and I understand your videos so much better and I understand my other studies better because it’s changed the way I think about things

Surprising that you didn't mention Lene Hau at all. In 2001 she became the first person to stop light completely, using a Bose Einstein Condensate.

The trouble is light is invisible until it illuminates something visible, and once that's true, light has left the system because it's dispersing everywhere. So even if you successfully trap light in a perfectly reflecting fiber optic cable, it's such a tiny amount length wise that it would require an extremely slow motion camera to witness the exiting light illuminating anything.

The speed of light can be slowed down depending on the medium it travels through. This may be a fun concept to look into to further explore light confinement.

Action lab never fails to entertain and "enlighten" me 😀

The thickness of a fible optic cable core depends on what kind it is. If it is multimode, it is typically 50 microns which is around the thinkness of a human hair. Single mode cables are around 9 microns, a 5th (not a 10th) of a human hair. The closup you show is a thicker multimode one, the one you play with a single mode.

Great video ! I've worked with fibre cables for many years, but not seen some of the things you demonstrated today before.

Great demo of the general principles of fibre optics, and the behaviour of optical fibres. I enjoy this channel and hope it has lots of younger followers.

Just a thought that while light is entering the bend in the closed loop, it is also escaping through the same bend. You would need some kind of 1-way photon valve to do a proper test.

You explained this concept better than my physics teacher did when I went to school.

YOUR PRODUCTION QUALITY HAS INCREASED AND I LOVE IT.

Thanks for the great explanation. I’ve always found fiber optics fascinating.

I had the exact question of can we capture light, thanks for such an awesome video!

Always dreamed of "light trapping" but my theory utilized two way mirrors in a tetrahedron type of ball with multiple surfaces reflecting at many different angles. I do like the fiber cable experiment though AND you should visit Lucent Technologies in Georgia to get a longer fiber optic cable.

I was hiding behind the couch when you shot that powerful torch into the fibre . I was worried you would send the beam both ways at once and make a particle accelerator, and when the beams met they would produce a black hole and obliterate the earth. But you must have got the angle just perfect to only send it one way. Well done... talk about phew!

The idea of trapping light in a mirror room has toyed with my mind since I was about 8 years old. This video MADE MY DAY!

I know something similar to this happens with different kinds of light/electromagnetic waves such as the case with of the waveguide in a microwave oven that guides microwaves into the cooking chamber as well as the ionosphere that enables the long-distance propagation on longwave radio waves such as the ones used in A.M. radios.

Your topic matter is beyond amazing. I find it makes me ponder things I'd never even considered.

You're sharing basic science from 100 years ago with the public. Nice.

4:30 makes me think you might be able to see a faint glow from the coil of fiber if you look at it in a completely dark room.

We learn about refraction and TIR in class 7th or 8th in India But saw the fibre for the first time like this..... beautiful ❤

Im a network consultant so much of this is Knowledge ive already got, but wow, I never thought to test an SFP with a multimeter! Very good idea!

I like how you also actually explained the technology behind the sponsor's product, you know your audience!

The speed of light is just unfathomable 😮. Even after so many reflections, and a long fibre cable, the pass through after he connects the laser still seems instantaneous.

Wow! I knew how fiber optic cables worked but it did not occur to me to “store light” but on second thought I figured it would dissipate at some point because getting 100% percent “efficiency” just seems impossible.

One of my favourite channels. Thanks for your content.

What if the fiber core had some sort of shallow y-fitting where you inject it from the branch, and then the main line is the actual loop?

It is the experiment I imagined in sixth grade when I was first introduced by optic cables in my computer science class. I think you performed the experiment for me.

If the angle required is not too strict, you could design a Y connector that takes light from 2 sources into one outlet, then just loop that outlet into one of the intakes. That way you have one intake free to kick it off and any light will just go on and loop, without the need to connect/disconnect anything.

"I don't know if you've heard this already, but light moves really fast." ❤😂

Love what ur doing with changing the thumbnail to see the results vs the original

During the Apollo missions they left reflectors on the moon. They then shot a laser beam from earth at it to measure the distance to the moon very accurately. What they have effectively done is storing a beam of light for about 2.5 seconds.

Light changes speed through different mediums. Not sure if this would even be possible but a hypothetical material that slows down light to a literal crawl. Then you could "capture" some light from one place and let it out somewhere else.

Although it is a fun thought experiment, I think it is pointless to even try for another reason (but also connected to the lightspeed). Not only are the internal losses (cumulatively) so high that the energy dissipates almost instantly after killing the source, but I do believe that you physically cannot close the loop fast enough after shining light into it to even suggest there was a "stream of light circling in the loop (me paraphrasing)". The time you take to straighten out the fiber is something close to eternity in lightspeed terms. So it is safe to say that the optical fiber has gone dark beyond any all-day means of measuring long before you switched the lamp off at 8:26 ....

"I don't know if you heard this already, but light moves very fast"🤯

Holy crap! I've been theorizing for a few years about sending light through a coil, in a loop. This method could actually do it!

My Fish Aquarium always does this, and its really bright.

5:42 when people who didn't know this expected to see you do it physically ☠☠

A brilliant insight into fibre optics!

How can it be “perfect” reflection in water, glass, etc if you can see it? Wouldn’t that still mean there’s losses and it’s less than 100%?

Love your videos❤️❤️❤️

Interesting video, James, thanks!

Very effective demo.

My father developed a method to splice fiber-optic cables back in the early 80s when he was in the Air Force. Prior to that, full replacement was the only option. Because it was while on duty, he could not patent the process. However, he did receive a $10k "Ideas" award for his efforts.

I've always wanted to build my own home and use even cheaper plastic fiber optics that run from outside my house to the basement and center of the home to give off light during the day. Always thought how cool it would be to light up my house with the sun rather than electricity. And as i typed this, i thought why not have a centralized light source that can be "dampened" rather than individual lights in every room. Anyways, friday night thoughts are done. lol

Great optical fiber cable introduction

❤you can tell your viewers are passionate about physical science and accuracy, and that you encourage thought and discourse❤

Since there’s an “acceptance cone,” ( 3:20 )couldn’t you have one fiber supplying light next to the end of the loop? Would that technically build up how much light was in there?

Even if the trapped light did not dissipate, you would only see a few nano seconds of it when you let it out. So you probably could not see it anyways without a really really high speed camera.

"I don't know if you've heard this already but light moves very fast" -Action Lab 2023

That's very important to have a best idea of total internal reflection.

On top of being an incredibly informative and brilliantly interesting video as everyone of your videos always are that BEAR device is cool beans!

6:28 there was no need to show the video of your last colonoscopy... 😉

Damn, thought I could finally get my perfect light saber.

That’s what I work with daily. And you even had an SFP. That’s a bend insensitive type of wire meaning it’s less prone to loss with tighter bends. The fibers that travel kilometers are usually not bend insensitive due to cost and usually need to maintain a bend radius not smaller than a pop can. The light that travels through them is IR that is outside the range cameras can see. Some people don’t realize this and look into an open fitting thinking there is visible light. This is dangerous because the light is invisible yet high intensity and at the least will cause permanent blind spots in your eyes. What’s kind of crazy is the connectors must be impeccably clean to minimize loss. For this we use handheld microscopes and tip cleaners. Dust specs even 1/10th of that 1/10th “human hair” sized fiber will cause loss. Which can be easily picked up from air exposure. The style you have with the blue connectors are flat faced tips. The style more commonly being used today are green (apsc) which have slanted faced tips. This is to reduce reflectivity back into the fiber, upstream. Think of it like a window you when look outside. You can see some of your own reflection in the window depending on light conditions. But If look through a window off angle your own image isn’t directed back at you. One of the downsides to slanted connectors though is that when they meet through a bulkhead, they exert the pressure (psi) of the standing foot of an elephant against each other. The slants cause a slight diversion and the 1/10th human hair sized openings on the connectors tend to eclipse each other which is why mechanical connectors (splices) are inherent to more loss than fusion splices.

If 100% of the light is reflected off the surface of the water, we wouldn't be able to see it from above.

hello everybody my name is Markiplier

During the cold war on the West side of the Berlin Wall in remote areas of the wall the U.S. installed a Fiber Optic X,Y grid that was buried in the ground it was used for vehicle detection. The way it worked was that the Fiber Optic cable was laid out in an X,Y grid many meters wide that followed along the wall. The points where the X fiber crossed over the Y fiber was a grid reference point such as X1/Y1, or X10/Y20 , Y50/X32 and so on. The cables had light running through them all the time and the light level that was going in and was coming out of the cables was measured. If a vehicle drove over the cable the compression of the ground caused a reduction of the light level through the intersecting cables at or near the grid points where the vehicle was passing over the cable allowing the location of the vehicle to be determined using the grids closest reference points.

We had really long rolls of optical fiber at work years ago, maybe 50 kilometers. It was unsheathed and spooled in a plastic box so it wasn't that big. We used it for testing fiber communications equipment in a lab with latency like you'd get once installed in the real world. We never tried looping it but I bet the lasers would not have made it around those spools too many times. It'd be detectable with equipment (optical time domain reflectometer) but not visually. Some of the equipment also contained sections of doped fiber that were pumped by a laser of a different wavelength and those could actually amplify the light in the fiber without converting it to an electrical signal first. That would have been interesting to connect in a loop but we didn't. Most long haul laser communications gear will power down the lasers if they don't see a valid signal, that's to protect the eyes of the technician who unplugs the wrong patch fiber and looks at it.

Could you use that to see the speed of light if you just had a long enough roll of that cable?

Awesome thought experiment! i learned two things - why fiber needs to have repeater/amplifiers every several km, and - most importantly, i can purchase a device that will turn my 60+y old face, into someone only 20! its an awesome day, today! (seriously, i always enjoy your video's! it is so exciting for every youth - for me, it was transistors at they time they replaced vacuum tubes/valves! God bless you!

Amazing. I always wondered about this.

One of my friend's dad is a fiber optic worker and one time he let us learn and fuse the glass. It was way cool.

My ISP literally just routed a naked optic fiber into my apartment, hot-glued it directly onto the wall and around the doors, and plugged it in, no shielding whatsoever, it also has a bend like the one you made hardwired into the receiver piece AND my cat chewed on it a few times with visible damage to the core haha, but miraculously I have a working gigabit connection and no latency issues etc.

"what's your idea to store light for as long time as possible in a confined space?" me: light bulb

Know what I'd love to see? A cable 186k miles long, culed up, so that if you shine light in one end, you'll see it come out the other a second later.

LoL tomorrow I have physics exam and question on these topics is going to be asked. What a perfect timing this video landed on KZfaq!

Wow that's actually amazing that it's generating a voltage with the transceiver and nothing else. Light really is something else.

This also reminded me of Dr. Mallet's time machine made of looping laser light (it supposed to 'stir up' spacetime enought to connect the moment machine has been turned on with the present moment...).

Nice Video! Thanks!

As a systems administrator, I deal a lot with FOC's. Let me tell you, its so much easier to work with as if theres a sever in the line, you can find out exactly where it is

I get my internet from a small neighborhood ISP whom I worked with for a short period of time. One time he was checking a fiber optic cable to see if it works: He took out an end from his device and plugged it into a little laser then put it on his desk, afterward we both got in the car and drove many streets away to a rather far location, he climbed on the pole took down a connection unwrapped the cables and started looking... there it was, the blinking red light on the other end. I found it fascinating to think how a small battery powered laser in the building far away was shining through a wire far away, it made perfect sense but felt like magic at the same time.

Absolutely LOVE the shirt!

"AH HA, I'VE DONE IT, I'VE TRAPPED LIGHT IN AND ENDLESS REFLECTIVE LOOP!" "Cool, can we see it?" "Well... no."

I thought you would make a 3-way adapter to "inject" the light, but hitting that critical angle might be hard. Oh well🤷🏽‍♂️

You make science fun.

Could you make a video about pentamirrors and how they work compared to pentaprisms? Refraction is also very interesting phenomenon - note that the angle of refraction actually depends on wavelength and this is why optical prism decompose white light into a rainbow. Little people can explain why this happens actually. The physics behind this phenomenon is interestingly tricky to explain and understand. The refraction angle in air/glass interface also changes wildly outside visible spectrum - this is one reason why windows are transparent for visible light but partially reflect infrared and UV light.

Phosphorescent materials, known as glow in the dark pigments, are the answer to the question at the end of the video. They absorb light at a short wavelength and emit it at a longer wavelength that they shouldn't be able to, so the light they should emit is trapped and leaking out slowly due to quantum effects.

Great video!

I remember the Slow Mo Guys doing something a while back to slow light right down so they could record it. It was a while ago and I forget exactly what was involved, but I wonder if that could somehow be combined with this so the light would take longer to decay and thenyou could maybe store it for a more significant number of seconds 🤔

That was very interesting.

I'm so used to fiber optic cables that my first reaction was, "what's the big deal?"

I thought the bend radius on fiber optic cables had to do with them breaking, but I guess the signal is severely degraded first.Thanks, Great video.

Amazing work. ❤❤❤

Bro just created the Lasso of truth!

Great video

The person who will discover something 100% reflective will create the future as we’ll finally have something to store electricity efficiently

it's funny how easily you can do the nicest experiment

Bro, your so smart. I'm surprised you haven't figured out anti-gravity.

I work with fiber cable too. Each splice or termination introduces loss and reflections. Much more than a long section of cable.

My brain has imprinted the dogma "THOU SHALL NOT KINK GLAS FIBRE CABLES" so much that I felt a bit of pain when you did exactly that. :D

Another awesome video.

I saw this once when our home wifi was being fixed. The guy shone a laser light through the fiber optic line to find the faulty/broken parts of the wire. The red light in the faulty sections can be seen close and far. It was amazing to see it in person.

Reminds me of a concept called "slow glass" from an old Sci-fi series of short stories (Bob Shaw). Basically it took decades for the light to travel through the glass, so people used them to replace their windows.

To store the light in a confined space, you need to make it so the loops essentially refresh the light. Its not enough to have total reflectance in the cable..SOME of the light has to be leaked out and back in again at set intervals in the cable to refresh. The "lost" light has to "rejoin" light that had previously lost some of its luster to add up to brighter light. Think of it like a helix. you need an inner and outer carrier area of light in the optical cable that trades light back and forth to maintain brightness.

This reminds me of a Finnish children's story about a family of fools. They built a house without any windows and tried to solve the problem by trapping sunlight into a bag and carry it in to the house.