Kenneth, "... I keep reading that metro DWDM requires that new fiber be laid and that cost is why deploying additional SONET with dark fiber remains cheaper."
Huh! That don't compute.
You surely must have misunderstood something in the translation.
This might help clarify your misconceptions, and prevent poisoning the minds of children and the uninformed.
1. SONET (Synchronous Optical Networking) gear costs two to ten times as much as DWDM for equivalent capacity, and it also requires optical fiber.
2. "Dark Fiber" is installed, but unused fiber. It is called dark because there are no modulated laser light signals passing through it. How can it possibly be cheaper than anything? By definition, it is infinitely expensive. Division by zero equals infinity.
3. Metro optical networking demands are rapidly increasing (see my earlier post today) largely due to Internet traffic. These demands can be met by one of three methods:
a. adding more fiber (a fatter pipe),
b. adding more wavelengths (optical multiplexing), or
c. increasing the channel capacity (not to be confused with speed)*, ie 10 G to 40 G.
To put things into perspective SONET gear is big, expensive, power hungry, dumb, and optimized for voice service. The equipment is configured in a very ridgid interlacing ring architecture, that often requires MONTHS to reconfigure.
By contrast, DWDM equipment, has a much smaller footprint, uses considerably less power, is considerably less expensive, is very easy to install, and has imbedded intelligence that permits instantaneous configuration by point and click using a personal computer, if not automatically upon traffic demand.
DWDM was designed to conform to SONET protocol standards, and therefore carries voice, but is optimized for data service. DWDM can be configured into a SONET ring architecture, and frequently it is. It can also be configured for point to point, or a mesh network. DWDM is ideal for data traffic, which is growing at orders of magnitude greater than voice traffic.
Now, if you were building out a new network, which would you choose? To me, at least, the answer is obvious. On the other hand, if you had a 100 year old telephone network, then you might consider adding some SONET gear, since this architecture is what you currently have, and its all you know. Otherwise, you can use that stuff for a bouy anchor.
Jack Hutchison
* Bandwidth is capacity, not speed. Speed is something else again. Since light travels at the speed of light, it cannot be made to go any faster (to increase capacity). In spite of what you might have read elsewhere, electrons also zip along at the speed of light. So why the fuss about the OEO interfaces?
That's another lecture. |
