[LINK] fibre distance issues?

[steve jenkin]

Richard Chirgwin wrote on 24/10/07 8:28 PM:

> Well, I have no idea what the "1.5 km" statement means. That sounds
> distinctly like scrambled technical information to me!

Could be true if Telstra are using some cheap system.  [Sound familiar?]
But the cost is dominated by bundling fibre and laying the cable - 5-10%
more for a unconstrained system.

And wouldn't a sensible design use *commodity* products/standards like
802.11 ethernet??

There are many sorts of transceivers.  Longer range == higher cost.
Highly non-linear.
EG:
<http://en.wikipedia.org/wiki/10_gigabit_Ethernet>
<http://www.cisco.com/en/US/products/hw/modules/ps5251/products_data_sheet0900aecd801f92aa.html>

And "fibre ain't fibre":  multi-mode, multi-mode graded index, single-mode.
Again Longer range == higher cost.
<http://www.fiber-optics.info/articles/fiber-types.htm>
<http://en.wikipedia.org/wiki/Optical_Fiber>
<http://en.wikipedia.org/wiki/Multi-mode_optical_fiber>
<http://en.wikipedia.org/wiki/Single-mode_optical_fiber>

The real value in FO systems these days is using
Wave-Division-Multiplexing [different frequencies]
There's coarse (cheap) and dense (not cheap).
Again More bandwidth == higher cost.
<http://en.wikipedia.org/wiki/Wavelength-division_multiplexing>

Adrian Blake around 2000 designed a 4-loop system to connect the town of
Cooma.
He paid AGL to lay empty conduit when they laid gas pipes. Fibre to be
blown in later.
His design used ethernet and WDM. Telstra has since acquired the conduit.
<http://www.computerworld.com.au/index.php/id;972698106>

Project was a casualty of the Tech Wreck - project funding was pulled.
[Same as Transact]

cheers
s

-- 
Steve Jenkin, Info Tech, Systems and Design Specialist.
0412 786 915 (+61 412 786 915)
PO Box 48, Kippax ACT 2615, AUSTRALIA

sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin