Re: [Starlink] mems optical switching

[David Lang <david@lang.hm>]

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Their coverage of the poles and oceans is growing outside of the 'bent pipe' 
model, so I think that's proof that they are working.

I am in southern california and commonly go out a gateway in vancouver BC, I 
think that's more than a simple bent-pipe hop away.

David Lang

On Mon, 20 Mar 2023, Dave Taht via Starlink wrote:

> Date: Mon, 20 Mar 2023 04:32:19 -0700
> From: Dave Taht via Starlink <starlink@lists.bufferbloat.net>
> Reply-To: Dave Taht <dave.taht@gmail.com>
> To: Christian von der Ropp <cvdr@vdr.net>
> Cc: starlink@lists.bufferbloat.net
> Subject: Re: [Starlink] mems optical switching
> 
> 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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>
> -- 
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> Dave Täht CEO, TekLibre, LLC
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