lemm.ee

9 points

6 months ago

I’m highly suspicious about group dispersion over long distances. Today’s infrastructure was developed for a certain range of frequencies. Broading it right away wouldn’t be applicable that easy - we would need to introduce error correction which compromises the speed multiplier.

Too lazy to get the original paper though

report

[ - ]

blarth@thelemmy.club

4 points

6 months ago

We already have transceivers that perform forward error correction. That technology is a decade+ old.

report

[ - ]

4 points

6 months ago

It is, but it compromises the speed exponentially with length/broadening

report

[ - ]

blarth@thelemmy.club

1 point

6 months ago

Dispersion compensation and FEC are separate layers of the cake, and work hand in hand.

report

[ - ]

-1 points

6 months ago

I don’t understand why, tho I do not have any kind of expertise here.

I suggest (Haven’t read it), this paper proposes to send much denser and broadened signals around one carrier frequency (they use single mode). Due to dispersion they

Start to overlap with one each other. If you put more frequencies, you would have more overlaps and I fail to see how it won’t lead to errors.
They all arrive at the broader time window, which again could be mitigated either by error correction, or by extending the time window.

report

[ - ]

CileTheSane@lemmy.ca

8 points

6 months ago

“I haven’t read it, but I assume these are things they didn’t take into account.”

Okay then.

report

[ - ]

0 points

6 months ago

Okay, let’s read and find out whether we can find something that we don’t know.

There’s no paper, there is no letter, it’s a simple statement at the institute page. The way science is being communicated nowadays is frustrating.
From the statement

However, alongside the commercially available C and L-bands, we used two additional spectral bands called E-band and S-band. Such bands traditionally haven’t been required because the C- and L-bands could deliver the required capacity to meet consumer needs.

So they indeed broadened the frequency range.

They also did not say anything about limitations. They just pushed this bizarre number everywhere 🤷🏼‍♂️

report

Kazumara@discuss.tchncs.de

Show more comments

[ - ]

2 points

6 months ago

The zero dispersion wavelength of G.652.D fiber is between 1302 nm and 1322 nm, in the O-band.

Dispersion pretty much linearly increases as you move away from its zero dispersion wavelength.

Typical current DWDM systems operate in the range of 1528.38 nm to 1563.86 nm, in the C-band.

Group dispersion in the E-band and S-band is lower than at current DWDM wavelengths, because these bands sit between the O-band and the C-band.

report