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To: craig crawford who wrote (1430)	2/22/1998 6:43:00 PM
From: George Dawson	Respond to of 12623

craig, According to IEEE Communications (Feb 1998): The problems in moving to OC-192 include: 1. Engineering problems 2. Some of the installed fiber is unsuitable for 10 Gb/s speed. 3. Span engineering and the need for signal amplification and regeneration rise as the bit rates rise. The article actually talks about OC-768 and how most experts doubt that this will be possible in the forseeable future. Fujitsu, Nortel, and Hitachi claimed they had plans for 16 or 32 wavlengths at 10 Gb/s and MCI said it "wanted to" transmit 32 wavelengths at 40 Gb/s or 1.2 Tb/s per fiber. Clearly, at this point in time the market is so lucrative that many vendors are making claims that do not take points 1-3 into account or the fact that they do not have a product ready to sell. George D.

To: craig crawford who wrote (1430)	2/22/1998 6:47:00 PM
From: Tim Bagwell	Respond to of 12623

I think QWST is running OC-192 because they are laying new fiber which is well-suited to handle OC-192 speeds. Craig, You explained it well. The QWST fiber has lower dispersion so they can run at OC-192 over long distance. AT&T et al. have older fiber and are probably limited to OC-48 without dispersion compensation. Dispersion compensation is possible and many companies are developing components that perform this function. But it's a complex subject and it has a big impact on the complexity of the fiber network. I would think that the older networks will try to live with OC-48 and crank out more channels. It depends on the particular segment of fiber. The longer the link the more challenging it is to stuff bits down the pipe.

To: craig crawford who wrote (1430)	2/22/1998 7:15:00 PM
From: Gary Korn	Read Replies (2) \| Respond to of 12623

Furthermore AT&T has some of the oldest fiber in service. From what I have read some of their fiber might not even be in good enough condition to even run at OC-192 speeds. Therefore solutions running at OC-48 would be the only effective solution. I don't know how much of the installed fiber is not suitable to run at OC-192 but I would bet it's enough to make a difference. Craig, Thanks for pointing this out. When I read about the aging of fiber, and how some simply is not suitable for OC-192, I was wondering how long fiber lasts and/or if newer fiber manufacturing processes are better. Edited: In reading Tim Bagwell's post, it seems that the aging of fiber may not be the issue. Rather, the issue may be the quality of the original manufacturing process (in terms of dispersability). I think another issue is how fast you want to speed up the train. That is, LU's solution (when it exists) might works for some, but not all, portions of the railroad. That is, it may best work where the need to let off data passengers is diminished. (As I understand things, the faster you run the train, the less granularized are the data packets that you offload). Gary Korn