are underwater routers a thing?

Joel Jaeggli joelja at
Fri Mar 18 04:21:56 UTC 2022

On 3/17/22 18:42, Michael Thomas wrote:
> I was reading an article in the Economist about a new fiber route down 
> the Red Sea from Israel and wondered if there were any branches off of 
> those lines and where the routers were for them. The route kind of 
> made it look like it was completely at sea, but it would kind of make 
> sense to leave them at sea if you could put a router there.

There's a limited number of possible branches on a cable and as a result 
you just put the routers on the edges rather than in the middle. What 
you do put in the water is something like:

The more the active electronics are at the ends rather than in the open 
ocean the greater the serviceability is and also over the lifetime of 
the cable the easier it is to upgrade it to higher capacity as the data 
bearing capacity of a given wavelength increases. The FLAG cable has had 
for example has has several capacity increases over it's service life 
which closing in on 25 years at this point.

Amplifiers are still necessary for longer spans but a lot of other logic 
is not. for situations where the distances are manageable passive 
unrepeated systems are greatly prefered because it keeps servicing due 
to electronic faults to a minimum and reduces the cost accordingly. see 
the recent tonga cable fault and repair for a passive system.

The mean depth of the worlds oceans is around ~3700 meters below MSL 
which means most service calls involve deploying to the proximate 
location of the fault, fishing around for a while and then carefully 
re-laying  several kilometers of cable on a splice has been made. which 
typically takes weeks.

> Mike

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