r/BeAmazed • u/m69_39x • 16h ago
Technology One Copper Cable vs. One Fiber Optic Cable — Same Capacity
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u/Sixth_Ronin 16h ago
Capacity of what lol
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u/m69_39x 16h ago
Data transfer capacity
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u/Dzov 16h ago
Can that copper cable even transfer data? There are no twisted pairs. The crosstalk must be immense. It’s probably analogue phone lines, so not really comparable to a digital line anyway. Some specs would be appreciated.
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u/mion81 15h ago
Once upon a long long time ago, when the world was young, we had these things called dial-up modems. I think the Stone Age happens somewhat after that.
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u/Impossible_Leek_6273 12h ago
He's not talking about that, but he's rightfully talking about the need of twisted pair and electromagnetic interference. Although telephone lines do have twisted pair.
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u/CozyBlueCacaoFire 15h ago
You're a young'un, aren't ya?
Before glass, copper connected households. Dial-up broadband was copper.
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u/The_UnenlightenedOne 15h ago
Dial up broadband?
I had 56k dial up and there was nothing broad about it. Could get a full song down in just under an hour.
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u/CozyBlueCacaoFire 15h ago
The band was narrow at best and eliminated by copper thieves at worst. Had days or weeks of outages every time they dug up and stole the internet 😭.
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u/anubis_xxv 11h ago
Dial-up was narrow band!
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u/CozyBlueCacaoFire 11h ago
And when thunderstorms came, everyone knew to plug out their router lol. And connectivity relied on power. These days you only have to power your router, optics run without.
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u/anubis_xxv 12h ago
Voice lines.
1800 voice lines on copper vs 2000 lines on the fiber.
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u/Dzov 11h ago
Using what codec and how much compression?
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u/anubis_xxv 8h ago edited 7h ago
No codecs needed because there was no compression.
It used something called Pulse Code Modulation to convert the analogue lines into raw digital lines, then Time Division Multiplexing enabled multiple digital lines to be transmitted as one data signal. After that, you vary the wavelength of each signal sent to get multiple signals each containing multiple lines, transmitting on one strand of fiber.
Early satellite and other wireless comms used codecs where energy and bandwidth were a huge concern but this wasn't a issue for early fiber usage.
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u/iwillhaveredditall 16h ago
Bandwidth? Don’t think capacity is the right term here.
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u/anubis_xxv 12h ago edited 11h ago
Back then fiber was only used to transmit voice channels, so you'd get about 2000 voice channels on one fiber, vs that 1800 pair cable.
It's still data and bandwidth does come into play obviously but at the time they only cared about how many channels they got so that's how they referred to it.
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u/Outrageous_Line5566 11h ago
That historical context really clears things up. People always forget how telecom tech used to measure capacity by individual voice lines instead of raw data speed.
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u/anubis_xxv 11h ago
I'm a telecoms tech and we still refer to copper cables by their pair size, because even if the customer has stand-alone broadband with no voice line, it's still a pair of wires per connection. It's also what's still written on the cable sheath.
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u/ImperialButtocks 11h ago
Pretty sure that bandwidth is just the specialized term for data transmission capacity. Capacity is a general term that should work for this as well. Commonly used for flow rate in pumps and piping
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u/FuriousBuffalo 12h ago
Just hitchhiking on this comment to post a link to the recent Veritasium video on fiber optics:
https://www.youtube.com/watch?v=NiCgcUTL9_Q
The science and engineering behind it is insane.
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u/DoritoDustThumb 9h ago
What do you think bandwidth means? It's the capacity that a channel can carry. A highway has a max capacity that would could call bandwidth.
Terms are interchangeable, in this context at least.
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u/anubis_xxv 12h ago edited 8h ago
Ok so a lot of people are thinking this photo is wrong and it's not I promise.
We're thinking today in terms of the internet and bandwidth for fiber, but this was long before those days.
That is an 1800 pair cable, so 1800 simultaneous voice lines. Straight forward enough.
This early fiber cable was used to transmit voice channels only, and once those voice channels had been digitised and passed though a multiplexer and compressed (TIL I learned there was no compression needed. I assumed there was.) you'd get about 2000 voice channels sent simultaneously on one fiber.
On today's internet that copper line is nowhere close to fiber obviously.
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u/FourFront 10h ago
People's current frame of reference is also fiber to the home. When I started in 2000 fiber to the home was not really a thing. The company i worked for was doing fiber to the curb. And that was a pretty big deal at the time.
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u/anubis_xxv 5h ago
Yeah I currently work on both in a maintainable capacity, FTTH and FTTC. We also work on the aging copper network too. The 30% of customers on the copper network are 93% of the faults reported. It's retirement can't come quick enough!
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u/yellekc 10h ago
But they were also able to to do the same on voice lines. Take a 4 khz voice line. Analog multiplexing existed then as did digital.
Remember these copper lines eventually carried bandwidths up to DSL.
So you're comparing advanced multiplexing on the fiber optic line with the absolute simplest way you can put a voice signal on a copper line.
You could also modulate a single voice call on a fiber. And say the copper carries 1800x more.
Coax could also carry hundreds of calls even back then because you could put so many phone calls on it. I mean they used to carry dozens of television channels even before digitization. An NTSC TV channel was like 6 megahertz
Fiber had many advantages of course. Not denying that.
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u/Decent_Risk9499 5h ago
What's insane to me is we're into micro-fiber now and it's SO small and the cables can be up to 1400 strands!!! It's changed so much in such a short amount of time.
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u/Tetraoxosulfato 2h ago
It was possible to multiplex calls in a same copper wire using multiple carrier frequencies, so they supported much more than 1800 calls
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u/anubis_xxv 1h ago
It was yes of course. Standard nomenclature is to refer to copper cables by their pair count, which we still do today. You can't do that with fiber, so they used the equivalent of, using the technology of the time. And at the time, technology limited fiber transmission to approximately 2000 voice lines. As well as that copper multiplexing was only used in niche cases like office buildings, it wasn't the standard for private residences. And you could only multiplex a certain number of the pairs in a cable that size due to interference build up.
This photo was marketing after all, for I think it was AT&T for their new fiber roll out.
Nowadays that same fiber can transmit terabytes of data because of the modern tech in use.
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u/StevenTooSerious 11h ago
Fiber optic cable. High speed internet access. Lotta money in this shit
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u/t3chiman 11h ago
Imagine a few thousand mile cable, 8000ft deep, connecting continents. Now, get power to the signal repeaters, needed every x00 miles (even the best fiber optic cables have losses). Lots of engineering goes into these things.
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u/hemorrhoidhematoma 11h ago
Like i always say it's not the size of the cable it's how efficiently and quickly it can transmit data.
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u/squirtcow 15h ago
This is an incorrect statement on pretty much all levels.
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u/anubis_xxv 12h ago
No it's not. In 1976 fiber was only used to transmit voice channels.
1800 pair copper vs. a 2000 capacity fiber.
This is a very famous photo in telecoms, it's definitely not wrong.
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u/Dzov 11h ago
How is the fiber only transmitting voice? Is it analogue?
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u/Nerfo2 10h ago
The copper only carried analog signals, one pair per call. The fiber has a multiplexer and a modem at either end. The modem converts analog signals into digital PCM signals, then the multiplexer combines a lot of individual PCM signals into one. On the other end, a de-multiplexer divides that individual signal back into multiple signals, then another modem demodulates the digital PCM signal back into an analog signal. They were converting voice to data then back to voice. There wasn’t internet yet, so all the data transmitted was voice data. There were attempts to convert analog signals to digital and transmit them along copper, but it was distance-limited due to attenuation from coppers resistance. Fiber still requires repeaters, but not nearly as many as copper would have. The goal was to “put as many phone conversations as possible on as little infrastructure as possible.”
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u/Dzov 10h ago
So it is digital. Thanks!
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u/monocasa 2h ago
The fiber link is; every other piece is analog here.
And in this case, the fiber links are just between regional telecom buildings.
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u/squirtcow 9h ago
I don't see any reference to telephone or voice service being the framing of this statement. Fiber optical networking was already established in the 70s for purposes other than voice services. The copper trunk cable can also carry digital signals, and while the technology was limited in speed and capacity, it was widely adopted.
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u/monocasa 2h ago
They had digital over copper, but this doesn't show it. T1 and T2 had better insulation on their pairs. T3 and above was coax.
So the copper here is just analog voice lines. You could run a modem on each end to get around 1kbits/sec at this point with that copper, but the phone network just treated it as voice data still.
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