Terabyte Internet Speed

I wish that I had this at home Terabit Internet

* Danny M *

Edited By Danny M2Z on 26/05/2020 08:30:39

Edited By Danny M2Z on 26/05/2020 08:31:01

Wow !!

But do remember that they’re quoting bits not Bytes

MichaelG.

Duly noted and edited Michael. It's still a fantastic development in communication technology.

* Danny M *

Agreed !!

I wasn’t being picky ... just sharing a crumb of comfort, to soften your envy.

MichaelG.

I now have up to 223 Mbits and the only benefit which I have noticed is the speed which an ISO of Windows 10 pro 64 downloaded. Most websites don't seem to be any faster, probably because of their limitations. Big businesses can use these speeds as they have thousands of connections simultaneously.

It's worth looking at the original paper. What they have developed is a neat way to implement dense "wavelength division multiplexing" on a fibre in a way that can in principle built on a chip. It's transmitting 80 optical "carrier waves" with different wavelengths (i.e. colours) down a single fibre. This is a common technique, but they can do it with more carriers and so send more data, and potentially using a single chip. At the moment they are (as far as I can tell) modulating all the carriers with the same data for test purposes - perfectly valid as a research approach but for practical applications each carrier needs to be separately modulated with different data. Straightforward in principle but quite a big engineering step.

This sort of approach is very useful in the trunk network where it's worth spending lots of money at each end of an existing fibre link carrying vast amounts of data between big routers ("exchanges" rather than putting in a new multi-fibre cable, unlikely to be much use in the local network to your house where, once you have a fibre, the main limitations are the routers in the exchange and your house, and the servers you are accessing. Usual breathless reporting from BBC, not helped by somewhat sensationalist PR from the research team.

You can transmit white light through optical fibre, as well as some infra red and ultra violet, if that is not the complete spectrum, I don't know what is. More than 80 and with usable separation and bandwidth.

That's right, but the problem is that different wavelengths travel at different speeds ("dispersion", and the attenuation for many of them is rather high (we are talking about "windows" tens or hundreds of km thick here). Dispersion limits the maximum data rate you can send on one wavelength because the pulse "smears out".

Comms fibres are made to have low attenuation in fairly narrow bands generally in the IR spectrum around 1500 nanometres. According to Wikipedia modern WDM systems have up to 160 channels.

I am a couple of years rusty on my optical networking. I spent nearly 20 years on the practical side of this field.

Optical networking is typically either single channel or WDM - Wave Division Multiplexing, where you send multiple wavelengths down the same cable concurrently. Each wavelength (channel) carries a stream of data. The single channel systems are typically 850nm or 1310nm (visible light is about 400-700nm with 700 being at the red end) 850nm is used for short haul, a few 10's or 100's of metres depending on the link speed. 1310nm is long haul, potentially up to about 120km with standard transceivers and much further with high powered devices. WDM is either coarse or dense depending on how many channels you can get onto one fibre, 8 channel systems are relatively low cost and the cost rises with how many channels you add. They can also be passive or active depending on whether they just use what is effecively a prism to combine and split the multiple signals at each end or a more complex system. WDM systems typically sit between 1310 and 1550nm.

Most of these systems use one optical fibre to transmit and one to receive. I am typing now on a FTTP home broadband connection that that transmits and receives on the same fibre strand concurrently, which takes a bit of getting your head around, This is a form of WDM in that the TX and RX frequencies are different and filters in the transceivers prevent interference

As John says above the cable losses and various other optical factors significantly vary by frequency, which does affect how far you can transmit data and how many channels you can squeeze in.

Just musing but ... it seems to me that the capacity of the world wide internet infrastructure depends not only on the number of people using it and their activities but also on the data speed. Doubling the data speed effectively doubles the capacity, which alone may be a good reason for increasing speeds regardless of whether most users can actually capitalise on those speeds.

Or maybe that's stating the obvious