Re: Past one terabit/second on fiber

[droelke@rdxsunhost.aud.alcatel.com (Daniel R. Oelke)]

> 
> In the April 1996 issue of Fiber Optic Product news, there is an article on 
> a Lucent Technologies (formerly Bell Labs...no relation...sigh...) product 
> which wavelength-multiplexes quantity 8, 2.5 Gb/second signals on a single 
> fiber, for a total of 20 Gb/sec.  This is a real, purchaseable system.  On 
> the same page is a somewhat more experimental system, done by Corning and 
> Siemens, in which eight channels at 10 Gb/sec each were transmitted on a 
> single Corning fiber.
> 
> "Wow", I said.  Far faster than the 2.5 Gb/sec transmission that is 
> currently fairly standard for long-haul fiber trunks. 

The ads say they are selling it - that doesn't mean shipping it... yet
at least.  (Note that my employer is a direct competitor of Lucent 
so I have a vested interest in setting the facts straight)

> I wasn't prepared, however, for page 38, in an article titled "Research 
> Teams Achieve 1 Trillion bits a Second."  In fact, three separate groups did 
> this.  I copy the article below.

Yes - this is still very much a lab situation only though.
It will be quite a few years before we hit that in real systems.

[...]
> 
> Even if we only consider that 20 Gb/second fiber from Lucent, that is 
> equivalent to about 300,000 simultaneous voice calls.  

An OC48 signal (~2.5 Gb/sec) will handle 48 T3's or 48 * 672 voice calls.
Multiply by 8 for 20 Gb/second and you get 258048 voice calls.
Pretty close to 300k I guess.

> With a standard, 
> 36-fiber cable, that represents 18x300,000 two-way calls, or about 4.8 
> million calls.  This is probably far greater than the maximum number of 
> people on LD in the US at any given time, and that's just a single cable trunk.

I don't know that any number fiber cable is "standard" but 
36-fiber cable is not unusual.  To find the capacity of a cable, you
have to cut the number of fibers in half (as you did) because
generally each fiber is used only for a single direction of traffic.
You then have to cut it in half again because phone companies have 
everything redundant.  So, for a connection between two cities,
there are generally 2 cables in different locations (so one backhoe
doesn't get both), with on average only 1/2 the fibers in each carrying 
paying traffic.

> If we assume that the fiber cable costs $1/meter per fiber, and the cost of 
> trenching, burial, and interconnects raise this to $10/meter/fiber, and if 
> we generously assume that the average LD call goes 3000 miles (5,000,000m), 
> that call occupies 1/150,000th of a $50 million fiber for a few minutes.  If 
> we suppose that the fiber has to gross $100,000,000 per year to pay for 
> itself, and even if it's only operating at an average 10% load level(both 
> assumptions are pessimistic, that only works out to a cost of 1.3 cents per 
> minute per call.  That's why these LD phone companies are so scared:  If we 
> can transmit Internet on fiber, that fiber can accept this extra traffic at 
> very low marginal cost.

I can't vouch much for your cost numbers - other than to apply the 
factor of 2 adjustment noted above.  I would add that much of a 
phone companies cost is in billing and customer service, etc.
Not the cost of installing and maintaining the fiber and equipement.

This is how the smaller carriers buy lots of bandwidth off of the
big guys, and remove all the billing, etc. problems to themselves.
They big guys are still making money selling the bandwidth, and the
little guy makes his profit by selling for slightly less
than the big guy and somehow making his billing, customer service, etc.
cost him less.

Internet telephony should make the use of bandwidth even more
efficient - thereby cutting costs.  The big guys who own
the fibers will still make money - the pipes that carry internet
traffic are still needed.  But the little guys will get squeezed out.
(until they become ISPs ;-).  Internet traffic could theoretically
be carried over this large amount of protection fiber (mentioned above)
that is out there for a much lower marginal cost than the current 
T3 or OC3 pipes that are being used.  The only "problem" being that these
are lower priority channels, so that if a failure occurs anywhere,
the traffic on them is dropped.  Most customers are demanding 
high uptimes so much that the idea of a very lost cost, 
but much less reliable service hasn't caught on yet.

Dan
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Dan Oelke                                  Alcatel Network Systems
droelke@aud.alcatel.com                             Richardson, TX