reply to post by Yknot
Yes, well done. I am aware of DWDM, it is used within SDH/SONET architecture and as stated, that is what I do for a living.
You also seem to be unaware of the difference between a link (such as STM-256) and a fibre. The 1.6 Tb system you describe will be made of multiple
STM-256, each an individual link in it's own right.
The Asian Terabit system you linked to earlier is a network
, in that it will have multiple elements and many links within it to give the
terabit capacity, but you will not get a single link giving you 1.6 Tb/s in SDH/SONET, but rather that is the total capacity
of the whole
Imagine a highway with multiple lanes. Each lane can only accommodate a certain amount of traffic, yet the whole highway has the capacity of every
lane within it. What you seem to believe is that the highway has no lanes and is just an open pipe with breakneck speed.
This is not so, it will be made at it's most basic level of VC-12 (2Mb/s) channels (which themselves contain 30 64Kb/s channels, but aren't
represented in SDH/SONET architecture), which are then multiplexed up into STM-1, STM-4, STM-16 etc up to STM-256 for transmission. There is no faster
STM frame than 256, which is roughly 40 Gb/s. Each of these will be bundled together on a DWDM element down the fibre, giving a total transmission
speed of every STM frame added together, which would be somewhere in the region of 1.6 Tb/s. Not the same as having a through 1.6 Tb/s link, as such a
thing is not possible.
Again, go read up on SDH/SONET, which is the standard for transmission all over the world. Also, look up the difference between capacity (which is a
network wide term) and then go look up the fastest individual SDH/SONET frame currently possible. Standards exist for STM-512, yet I do not know of
any vendor currently supplying equipment that can do this transmission speed. Each STM frame will be a single wavelength and a single link in it's
Just to make life easier for you:
Capacity: This is a measure of how much traffic a single network can carry in any given moment, but it is not an accurate description of the fastest
transmission speeds for individual links, as the capacity is the TOTAL
of all those links added together.
Rather like saying 5 cars can, between them, cover 500 MPH, but no single car can do that speed on it's own.
Now, I hope you can understand the above, as it seems that on this rather simple premise is what your basing you whole argument on.
[edit on 18/2/08 by stumason]