Re: [Starlink] mems optical switching

[Dave Taht <dave.taht@gmail.com>]

We haven't heard much about the starlink ISL links lately. Any sign
they are working anywhere yet?

On Sun, Mar 19, 2023 at 7:33 AM Christian von der Ropp via Starlink
<starlink@lists.bufferbloat.net> wrote:
>
> All-optical switching could greatly reduce complexity and power
> consumption on the satellites at the cost of flexibility. Up to 44
> satellites in an orbital plane would use individual wavelengths which
> would be passed on transparently down the daisy chain and only
> satellites in range of gateways would convert the optical signals back
> into electrical ones, and send them down to earth while they pass a
> gateway. This would result in relatively short duty cycles, hence less
> power draw per orbit and less heat dissipation issues.
>
> Actually I've been suspecting that the SDA targets all-optical switching
> for the Transport Layer constellation as I don't seen any other
> immediate reason for the requirement of their OISL standard to require
> wavelength switching within the ITU channel grid for LCTs (see p. 18 of
> the OISL 3.0:
> https://www.sda.mil/wp-content/uploads/2022/04/SDA-OCT-Standard-v3.0.pdf)
>
> As a matter of fact tuneable wavelenghts were already required in the
> draft version of the OISL standard published in April 2020:
> https://twitter.com/Megaconstellati/status/1310336728595562499
>
> -Christian
>
> Am 19.03.2023 um 16:16 schrieb Brandon Butterworth via Starlink:
> > On Sat Mar 18, 2023 at 03:19:49PM -0700, Dave Taht via Starlink wrote:
> >> Today, this about google's mems switching tech hit,
> > They've been talking about it since last year, seems to have got
> > a hype bump recently.
> >
> > Who expected circuit switching to make a comeback?
> >
> >> I keep wondering where else it could be applied.
> > They've been used for a long time, eg almost 20 years ago -
> > https://archive.nanog.org/meetings/nanog32/presentations/zwart.pdf
> >
> > There is a goal of optical packet switching, until then you're
> > limited to where there are limited flows of long enough duration
> > to make the change from packet to circuit switching viable. So mostly
> > automated testing.
> >
> > I've dabbled with the idea in an archive use case where very few of
> > a large set of storage nodes need to connect to a moderate number
> > of servers. For some cases we could have zero switches. The goal was
> > a mostly dark infrastructure and many 1000s of storage nodes,
> > removing the switches saves a lot of power.
> >
> > Commercial optical switches are expensive so I was looking at
> > making an optical strowger as I wanted a high fan out not
> > large n^2.
> >
> > In the mobile world they are looking at doing flexible bandwidth
> > per node with coherent optics over gpon fibre plant, allocating
> > variable amounts of spectrum to each, which could be adapted to a
> > similar circuit model. It'd be no use to google as they want the
> > full bandwidth between each node but as dwdm coherent optic costs
> > come down you could imagine doing the same with a full channel
> > between each pair, so like a conventional WSS but cheaper. If it
> > wasn't for the optics cost I suspect they'd have done that reducing
> > switching time to a channel change.
> >
> > brandon
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Dave Täht CEO, TekLibre, LLC