[geeks] Whee! Lightning strikes, AGAIN!

[gsm at mendelson.com]

On Tue, Jul 28, 2009 at 07:39:11AM -0400, John Francini wrote:
>
> Yes, there are.  (I use fiber 1- and 10-gigabit extensively (especially 
> the latter) at my work.)

Thanks.

> Interestingly, the IEEE proposals out there for 40-gigabit and 100- 
> gigabit talk about ganging 4 or 10 10-gigabit *fiber* connections  
> together -- I would have thought that they could just use multiple  
> colors (frequencies) over the *single* fiber without interference, using 
> prisms to join/split the colors.  Or am I being way too simplistic?

The problem is that all the current equipment is designed for one color
of laser. As 1000Base-T proved, it was much cheaper to gang 4 channels
together, which is basicly software, then produce something 10 times
the current speed. Two directions on the same pair was simple, telephones
have been doing it since the 1920's and 250mbit was not that much more
difficult in the late 1990's than 100.

The same with fiber. While it may not be colors, but different fequencies
of the same color (ok, that's still colors), some sort of splitter/combiner
would have to be designed and built. 

As long as I have room for the extra ports, and CPU power to combine them,
then ganged fiber is easily scalable. No new hardware is needed, and
software is (relatively) cheap.

In fact, if I were to make it think that the fiber links were ethernet and
used the same multiple card software that was availble by 2002, I could
do it with COTS (commercial of the shelf) technology. 

Building some sort of splitter/combiner setup is much more expensive as it
requires filters that may not exist yet, sensors and lasers tuned to different
frequencies, etc. 

At some point it becomes cheaper to design and build a "color multiplexed"
fiber optic system, but for cheap and rapid development, ganged multiplex
is "it".

This leads me into a rant about how people now just want to re-hash old stuff
(not my first choice of wording) than invent new. I'll spare you it.

Geoff.


-- 
Geoffrey S. Mendelson, Jerusalem, Israel gsm at mendelson.com  N3OWJ/4X1GM