In the Three Body Problem Trilogy by Liu Cixin some of the more advanced civilisations have the ability to change the speed of light locally with very interesting consequences for the that local space
I'm being vague to avoid spoilers, but I'll just say that it serves for a very interesting meditation on the concept of loss, and has stuck with me for the 5+ years since I read the trilogy.
Pedantic note: The speed of light in glass, optical fiber and water is different from vacuum (much lower). On a certain scale, humanity also knows how to locally alter the speed of light though not to this extent.
It's not actually that the speed of light in a singlemode fiber optic cable is slower, but that the photons aren't travelling in a direct path down the fiber like water down a pipe. They're bouncing off the interior walls of it at like a 45 degree angle billions/trillions of times before it reaches the other end of the cable.
Basically imagine like if you wanted to walk in a straight line between two points at both ends of a empty, long, narrow rectangular warehouse, and instead of walking in a straight line from A to B, you bounced off each wall at an angle (like a pool ball ricocheting off the bumpers) to get from one end to the other. Making your cumulative distance travelled on foot much greater.
>the photons aren't travelling in a direct path down the fiber like water down a pipe. They're bouncing off the interior walls of it at like a 45 degree angle billions/trillions of times before it reaches the other end of the cable.
I know there are many other mundane technologies that can be described in sci-fi-ish way, but for some reason I'm particularly amazed by fiber transmitters being compact and cheap enough to be used in mass-produced killer drones.
Not just that but your average russian or ukrainian used expendable munition UAV that uses a singlemode fiber spool uses the cheapest and most mundane of fiber transceivers. There's no requirement for data rates above 1 Gbps, so ordinary SFP optics (not SFP+ or anything) are used, and the distances involved means it works fine with a extended range 1550nm to 1610nm reach thing that can nominally handle 40 to 80 km of fiber.
When I say data rates are way below 1 Gbps, it's because commonly you've got two things going on, a UART serial bridge from operator to flight controller board (same idea as what is implemented in RF with ExpressLRS, TBS Crossfire or similar), this is at most a Mbps or two. Then a possible live video feed over IP which will be easily under 50 Mbps.
The only thing a little bit out of the ordinary about them is that they're often bidirectional single strand optics with the prism built in, and tx/rx on different wavelengths (like 1550 and 1570, or 1550 and 1610, or whatever). Basically same thing that somebody lighting a very low cost metro dark fiber circuit might do to use only 1 strand for a gigabit or 10 Gbps link.
You can get a pretty good 1080p60 video at only 6mbps. Depends on how well the sender is encoding I guess, but it shouldn't be too much more than that.
Some of the more basic ones are a very rudimentary NTSC analog video in to H264 encoder board that is tiny in weight and power consumption. They're using the same NTSC analog video-out forward flight cameras as are used in pure analog FPV. It's also not doing really 'complex' H264 encoding. Very similar to what you would get for the H264 encoder in a cheap $60 IP (RTSP) security camera.
There's more advanced ones that take video input from a MIPI digital video interface or native HDMI input.
Not just because latency but also because of cost, size, weight, power.
> They're bouncing off the interior walls of it at like a 45 degree angle billions/trillions of times before it reaches the other end of the cable
At the risk of exposing how little I remember from physics, doesn't light in a single mode fiber not bounce? (right about now I'm thinking that it's probably not great to think of photons bouncing because this is quantum level stuff, right? light is a wave, etc. gosh it's been a long time since I tried to really know any of this...)
The bouncing is more a metaphor, the refraction of light bending at an angle is sort of like how if you as an exterior observer look at a person who is standing waist deep in a very calm and clear swimming pool, their legs appear to be at a different position than their torso. Now imagine that 'bending' repeating trillions of times.
Right, and it varies with what type of glass, google "refractive index of glass".
If you google image search "refraction fiber optics" you'll get some decent pictorial examples of what I meant by photons bouncing off the interior walls of a 9/125 SM fiber optic strand billions/trillions of times on its path, I guess I was trying to write an extremely simplified explanation of refraction in something like a typical SMF-28e / G.652.D fiber.
You're conflating two very different meanings of "the speed of light". Confusingly, "speed of light" can refer to the universal constant, c, which does not change in glass, or to the speed that light travels in a medium. Here, we're talking about c. Relativistic effects are based only on c. The Three Body Problem trilogy plot device is also about c.
Our little project endeavours to digitise books from the erstwhile Soviet state which were published in many languages
We have, over the last 15 years, acquired/borrowed from libraries, and scanned a couple of thousand books on all topics of interest. All of them are out of print. Some of the physical copies were have, especially in indicate languages might be some of the few surviving ones
I have a macbook air from 2017. I use it when I travel, major work being done on a m4 mac mini. The issue is end of support for brew and many of the new/ latest apps not working but otherwise for simple things is works well
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